diff --git a/NEWS b/NEWS
index ef46b7e..afff79b 100644
--- a/NEWS
+++ b/NEWS
@@ -30,14 +30,20 @@ The following methods have been renamed:
 - GFilename::is_empty(), was GFilename::empty()
 - GFilename::url(), was GFilename::filename()
 
-The following classes now use for filenames a GFilename argument instead
+The following classes now use GFilename for filenames arguments instead
 of std::string:
+- GApplicationPars
+- GArf
+- GCsv
 - GEbounds
-- GGti
 - GEnergies
-- GEvents
 - GEventCube, GCOMEventCube, GCTAEventCube, GLATEventCube, GMWLSpectrum
 - GEventList, GCTAEventList, GLATEventList
+- GEvents
+- GGti
+- GLog
+- GModelSpatialDiffuseCube
+- GSkyMap
 
 The return value has been changed for the following methods:
 - GFits::filename() returns now GFilename instead of std::string
diff --git a/include/GApplicationPars.hpp b/include/GApplicationPars.hpp
index 51673fd..a1c7d3d 100644
--- a/include/GApplicationPars.hpp
+++ b/include/GApplicationPars.hpp
@@ -1,7 +1,7 @@
 /***************************************************************************
  *               GApplicationPars.hpp - Application parameters             *
  * ----------------------------------------------------------------------- *
- *  copyright (C) 2010-2015 by Juergen Knoedlseder                         *
+ *  copyright (C) 2010-2016 by Juergen Knoedlseder                         *
  * ----------------------------------------------------------------------- *
  *                                                                         *
  *  This program is free software: you can redistribute it and/or modify   *
@@ -33,6 +33,9 @@
 #include "GContainer.hpp"
 #include "GApplicationPar.hpp"
 
+/* __ Forward declarations _______________________________________________ */
+class GFilename;
+
 
 /***********************************************************************//**
  * @class GApplicationPars
@@ -49,8 +52,8 @@ class GApplicationPars : public GContainer {
 public:
     // Constructors and destructors
     GApplicationPars(void);
-    explicit GApplicationPars(const std::string& filename);
-    GApplicationPars(const std::string& filename,
+    explicit GApplicationPars(const GFilename& filename);
+    GApplicationPars(const GFilename& filename,
                      const std::vector<std::string>& args);
     GApplicationPars(const GApplicationPars& pars);
     virtual ~GApplicationPars(void);
@@ -80,10 +83,10 @@ public:
     void                   reserve(const int& num);
     void                   extend(const GApplicationPars& pars);
     bool                   contains(const std::string& name) const;
-    void                   load(const std::string& filename);
-    void                   load(const std::string& filename,
+    void                   load(const GFilename& filename);
+    void                   load(const GFilename& filename,
                                 const std::vector<std::string>& args);
-    void                   save(const std::string& filename);
+    void                   save(const GFilename& filename);
     std::string            print(const GChatter& chatter = NORMAL) const;
   
 protected:
diff --git a/include/GArf.hpp b/include/GArf.hpp
index 6809e15..00f1952 100644
--- a/include/GArf.hpp
+++ b/include/GArf.hpp
@@ -1,7 +1,7 @@
 /***************************************************************************
  *              GArf.hpp - XSPEC Auxiliary Response File class             *
  * ----------------------------------------------------------------------- *
- *  copyright (C) 2013-2015 by Juergen Knoedlseder                         *
+ *  copyright (C) 2013-2016 by Juergen Knoedlseder                         *
  * ----------------------------------------------------------------------- *
  *                                                                         *
  *  This program is free software: you can redistribute it and/or modify   *
@@ -29,10 +29,14 @@
 
 /* __ Includes ___________________________________________________________ */
 #include <string>
+#include <vector>
 #include "GBase.hpp"
 #include "GEbounds.hpp"
-#include "GFits.hpp"
-#include "GFitsTable.hpp"
+#include "GFilename.hpp"
+
+/* __ Forward declarations _______________________________________________ */
+class GFits;
+class GFitsTable;
 
 
 /***********************************************************************//**
@@ -45,7 +49,7 @@ class GArf : public GBase {
 public:
     // Constructors and destructors
     GArf(void);
-    explicit GArf(const std::string& filename);
+    explicit GArf(const GFilename& filename);
     explicit GArf(const GEbounds& ebds);
     GArf(const GArf& arf);
     virtual ~GArf(void);
@@ -56,20 +60,20 @@ public:
     const double& operator[](const int& index) const;
 
     // Methods
-    void               clear(void);
-    GArf*              clone(void) const;
-    std::string        classname(void) const;
-    int                size(void) const;
-    double&            at(const int& index);
-    const double&      at(const int& index) const;
-    const GEbounds&    ebounds(void) const;
-    void               load(const std::string& filename);
-    void               save(const std::string& filename,
-                            const bool& clobber = false) const;
-    void               read(const GFitsTable& table);
-    void               write(GFits& fits) const;
-    const std::string& filename(void) const;
-    std::string        print(const GChatter& chatter = NORMAL) const;
+    void             clear(void);
+    GArf*            clone(void) const;
+    std::string      classname(void) const;
+    int              size(void) const;
+    double&          at(const int& index);
+    const double&    at(const int& index) const;
+    const GEbounds&  ebounds(void) const;
+    void             load(const GFilename& filename);
+    void             save(const GFilename& filename,
+                          const bool&      clobber = false) const;
+    void             read(const GFitsTable& table);
+    void             write(GFits& fits) const;
+    const GFilename& filename(void) const;
+    std::string      print(const GChatter& chatter = NORMAL) const;
 
 protected:
     // Protected methods
@@ -78,7 +82,7 @@ protected:
     void free_members(void);
     
     // Protected members
-    mutable std::string m_filename;   //!< Filename of origin
+    mutable GFilename   m_filename;   //!< Filename of origin
     GEbounds            m_ebounds;    //!< Energy boundaries
     std::vector<double> m_specresp;   //!< Spectral response
 };
@@ -163,7 +167,7 @@ const GEbounds& GArf::ebounds(void) const
  * no load() or save() method has been called before.
  ***************************************************************************/
 inline
-const std::string& GArf::filename(void) const
+const GFilename& GArf::filename(void) const
 {
     return (m_filename);
 }
diff --git a/include/GCsv.hpp b/include/GCsv.hpp
index 74160b1..f45e6b7 100644
--- a/include/GCsv.hpp
+++ b/include/GCsv.hpp
@@ -1,7 +1,7 @@
 /***************************************************************************
  *              GCsv.hpp - Comma-separated values table class              *
  * ----------------------------------------------------------------------- *
- *  copyright (C) 2010-2015 by Juergen Knoedlseder                         *
+ *  copyright (C) 2010-2016 by Juergen Knoedlseder                         *
  * ----------------------------------------------------------------------- *
  *                                                                         *
  *  This program is free software: you can redistribute it and/or modify   *
@@ -32,6 +32,9 @@
 #include <string>
 #include "GBase.hpp"
 
+/* __ Forward declarations _______________________________________________ */
+class GFilename;
+
 
 /***********************************************************************//**
  * @class GCsv
@@ -57,7 +60,7 @@ public:
     // Constructors and destructors
     GCsv(void);
     GCsv(const int& nrows, const int& ncols);
-    GCsv(const std::string& filename, const std::string& sep = " ");
+    GCsv(const GFilename& filename, const std::string& sep = " ");
     GCsv(const GCsv& csv);
     virtual ~GCsv(void);
  
@@ -81,8 +84,8 @@ public:
     void        string(const int& row, const int& col, const std::string& value);
     void        real(const int& row, const int& col, const double& value);
     void        integer(const int& row, const int& col, const int& value);
-    void        load(const std::string& filename, const std::string& sep = " ");
-    void        save(const std::string& filename, const std::string& sep = " ",
+    void        load(const GFilename& filename, const std::string& sep = " ");
+    void        save(const GFilename& filename, const std::string& sep = " ",
                      const bool& clobber = false) const;
     std::string print(const GChatter& chatter = NORMAL) const;
   
diff --git a/include/GFits.hpp b/include/GFits.hpp
index 0fd62fe..56589bf 100644
--- a/include/GFits.hpp
+++ b/include/GFits.hpp
@@ -65,7 +65,7 @@ class GFits : public GContainer {
 public:
     // Constructors and destructors
     GFits(void);
-    GFits(const std::string& filename, const bool& create = false);
+    GFits(const GFilename& filename, const bool& create = false);
     GFits(const GFits& fits);
     virtual ~GFits(void);
 
@@ -107,11 +107,11 @@ public:
     bool               contains(const std::string& extname) const;
     const GFilename&   filename(void) const;
     int                extno(const std::string& extname) const;
-    void               open(const std::string& filename,
-                            const bool&        create = false);
+    void               open(const GFilename& filename,
+                            const bool&      create = false);
     void               save(const bool& clobber = false);
-    void               saveto(const std::string& filename,
-                              const bool&        clobber = false);
+    void               saveto(const GFilename& filename,
+                              const bool&      clobber = false);
     void               close(void);
     std::string        print(const GChatter& chatter = NORMAL) const;
 
diff --git a/include/GLog.hpp b/include/GLog.hpp
index a2a2136..96c3db2 100644
--- a/include/GLog.hpp
+++ b/include/GLog.hpp
@@ -1,7 +1,7 @@
 /***************************************************************************
  *                       GLog.hpp - Information logger                     *
  * ----------------------------------------------------------------------- *
- *  copyright (C) 2010-2013 by Juergen Knoedlseder                         *
+ *  copyright (C) 2010-2016 by Juergen Knoedlseder                         *
  * ----------------------------------------------------------------------- *
  *                                                                         *
  *  This program is free software: you can redistribute it and/or modify   *
@@ -30,6 +30,7 @@
 /* __ Includes ___________________________________________________________ */
 #include <string>
 #include <iostream>
+#include "GFilename.hpp"
 #include "GTypemaps.hpp"
 
 /* __ Forward declarations _______________________________________________ */
@@ -63,7 +64,7 @@ class GLog {
 public:
     // Constructors and destructors
     GLog(void);
-    GLog(const std::string& filename, const bool& clobber = false);
+    GLog(const GFilename& filename, const bool& clobber = false);
     GLog(const GLog& log);
     virtual ~GLog(void);
 
@@ -85,7 +86,7 @@ public:
     void               clear(void);
     int                size(void) const;
     std::string        classname(void) const;
-    void               open(const std::string& filename, const bool& clobber = false);
+    void               open(const GFilename& filename, const bool& clobber = false);
     void               close(void);
     void               flush(const bool& force = false);
     void               date(const bool& flag);
@@ -106,7 +107,7 @@ public:
     const int&         max_size(void) const;
     const int&         indent(void) const;
     const GChatter&    chatter(void) const;
-    const std::string& filename(void) const;
+    const GFilename&   filename(void) const;
 
 protected:
     // Protected methods
@@ -126,7 +127,7 @@ protected:
     bool        m_use_date;   //!< Dump date in prefix
     bool        m_linestart;  //!< Signals that buffer is at line start
     FILE*       m_file;       //!< Log file pointer
-    std::string m_filename;   //!< Log file name
+    GFilename   m_filename;   //!< Log file name
     std::string m_name;       //!< Name for prefix
     std::string m_buffer;     //!< Output string buffer
     GChatter    m_chatter;    //!< Chattiness for print() method
@@ -450,7 +451,7 @@ const GChatter& GLog::chatter(void) const
  * Returns the filename of the log file.
  ***************************************************************************/
 inline
-const std::string& GLog::filename(void) const
+const GFilename& GLog::filename(void) const
 {
     return m_filename;
 }
diff --git a/include/GModelSpatialDiffuseCube.hpp b/include/GModelSpatialDiffuseCube.hpp
index 83622b7..a75c4e3 100644
--- a/include/GModelSpatialDiffuseCube.hpp
+++ b/include/GModelSpatialDiffuseCube.hpp
@@ -1,7 +1,7 @@
 /***************************************************************************
  *        GModelSpatialDiffuseCube.hpp - Spatial map cube model class      *
  * ----------------------------------------------------------------------- *
- *  copyright (C) 2010-2015 by Juergen Knoedlseder                         *
+ *  copyright (C) 2010-2016 by Juergen Knoedlseder                         *
  * ----------------------------------------------------------------------- *
  *                                                                         *
  *  This program is free software: you can redistribute it and/or modify   *
@@ -39,6 +39,7 @@
 #include "GXmlElement.hpp"
 #include "GEbounds.hpp"
 #include "GEnergies.hpp"
+#include "GFilename.hpp"
 
 /* __ Forward declarations _______________________________________________ */
 class GFits;
@@ -60,8 +61,8 @@ public:
     // Constructors and destructors
     GModelSpatialDiffuseCube(void);
     explicit GModelSpatialDiffuseCube(const GXmlElement& xml);
-    GModelSpatialDiffuseCube(const std::string& filename,
-                             const double&      value = 1.0);
+    GModelSpatialDiffuseCube(const GFilename& filename,
+                             const double&    value = 1.0);
     GModelSpatialDiffuseCube(const GSkyMap&   cube,
                              const GEnergies& energies,
                              const double&    value = 1.0);
@@ -94,8 +95,8 @@ public:
     int                        pixels(void) const;
     double                     value(void) const;
     void                       value(const double& value);
-    const std::string&         filename(void) const;
-    void                       filename(const std::string& filename);
+    const GFilename&           filename(void) const;
+    void                       filename(const GFilename& filename);
     const GSkyMap&             cube(void) const;
     void                       cube(const GSkyMap& cube);
     GEnergies                  energies(void);
@@ -103,9 +104,9 @@ public:
     const GModelSpectralNodes& spectrum(void) const;
     void                       set_mc_cone(const GSkyDir& centre,
                                            const double&  radius) const;
-    void                       load(const std::string& filename);
-    void                       save(const std::string& filename,
-                                    const bool& clobber = false) const;
+    void                       load(const GFilename& filename);
+    void                       save(const GFilename& filename,
+                                    const bool&      clobber = false) const;
     //void                       read(const GFits& file);
     void                       write(GFits& file) const;
 
@@ -115,18 +116,18 @@ protected:
     void   copy_members(const GModelSpatialDiffuseCube& model);
     void   free_members(void);
     void   fetch_cube(void) const;
-    void   load_cube(const std::string& filename);
+    void   load_cube(const GFilename& filename);
     void   set_energy_boundaries(void);
     void   update_mc_cache(void);
     double cube_intensity(const GPhoton& photon) const;
 
     // Protected members
-    GModelPar    m_value;       //!< Value
-    std::string  m_filename;    //!< Name of map cube
-    bool         m_loaded;      //!< Signals if map cube has been loaded
-    GSkyMap      m_cube;        //!< Map cube
-    GNodeArray   m_logE;        //!< Log10(energy) values of the maps
-    GEbounds     m_ebounds;     //!< Energy bounds of the maps
+    GModelPar  m_value;       //!< Value
+    GFilename  m_filename;    //!< Name of map cube
+    bool       m_loaded;      //!< Signals if map cube has been loaded
+    GSkyMap    m_cube;        //!< Map cube
+    GNodeArray m_logE;        //!< Log10(energy) values of the maps
+    GEbounds   m_ebounds;     //!< Energy bounds of the maps
 
     // Monte Carlo cache
     mutable std::vector<double> m_mc_cache;    //!< Monte Carlo cache
@@ -226,7 +227,7 @@ void GModelSpatialDiffuseCube::value(const double& value)
  * Returns the file name of the spatial map cube model.
  ***************************************************************************/
 inline
-const std::string& GModelSpatialDiffuseCube::filename(void) const
+const GFilename& GModelSpatialDiffuseCube::filename(void) const
 {
     return (m_filename);
 }
@@ -240,7 +241,7 @@ const std::string& GModelSpatialDiffuseCube::filename(void) const
  * Set the file name of the spatial map cube model.
  ***************************************************************************/
 inline
-void GModelSpatialDiffuseCube::filename(const std::string& filename)
+void GModelSpatialDiffuseCube::filename(const GFilename& filename)
 {
     m_filename = filename;
     return;
diff --git a/include/GSkyMap.hpp b/include/GSkyMap.hpp
index c5a9218..de28ff4 100644
--- a/include/GSkyMap.hpp
+++ b/include/GSkyMap.hpp
@@ -33,15 +33,27 @@
 #include "GSkyDir.hpp"
 #include "GSkyPixel.hpp"
 #include "GSkyProjection.hpp"
+/*
 #include "GFits.hpp"
 #include "GFitsTable.hpp"
 #include "GFitsBinTable.hpp"
 #include "GFitsImage.hpp"
 #include "GFitsImageDouble.hpp"
-#include "GMatrix.hpp"
-#include "GVector.hpp"
+*/
+//#include "GMatrix.hpp"
+//#include "GVector.hpp"
 #include "GBilinear.hpp"
 
+/* __ Forward declarations _______________________________________________ */
+class GFilename;
+class GFits;
+class GFitsTable;
+class GFitsBinTable;
+class GFitsImage;
+class GFitsImageDouble;
+class GMatrix;
+class GVector;
+
 
 /***********************************************************************//**
  * @class GSkyMap
@@ -84,20 +96,20 @@ class GSkyMap : public GBase {
 public:
     // Constructors and destructors
     GSkyMap(void);
-    explicit GSkyMap(const std::string& filename);
-    explicit GSkyMap(const std::string& coords,
-                     const int&         nside,
-                     const std::string& order,
-                     const int&         nmaps = 1);
-    explicit GSkyMap(const std::string& wcs,
-                     const std::string& coords,
-                     const double&      x,
-                     const double&      y,
-                     const double&      dx,
-                     const double&      dy,
-                     const int&         nx,
-                     const int&         ny,
-                     const int&         nmaps = 1);
+    explicit GSkyMap(const GFilename& filename);
+    GSkyMap(const std::string& coords,
+            const int&         nside,
+            const std::string& order,
+            const int&         nmaps = 1);
+    GSkyMap(const std::string& wcs,
+            const std::string& coords,
+            const double&      x,
+            const double&      y,
+            const double&      dx,
+            const double&      dy,
+            const int&         nx,
+            const int&         ny,
+            const int&         nmaps = 1);
     GSkyMap(const GSkyMap& map);
     virtual ~GSkyMap(void);
 
@@ -148,8 +160,8 @@ public:
     const double*         pixels(void) const;
     GSkyMap               extract(const int& map, const int& nmaps = 1) const;
     void                  stack_maps(void);
-    void                  load(const std::string& filename);
-    void                  save(const std::string& filename, bool clobber = false) const;
+    void                  load(const GFilename& filename);
+    void                  save(const GFilename& filename, bool clobber = false) const;
     void                  read(const GFitsHDU& hdu);
     void                  write(GFits& file) const;
     std::string           print(const GChatter& chatter = NORMAL) const;
diff --git a/inst/cta/src/GCTAOnOffObservation.cpp b/inst/cta/src/GCTAOnOffObservation.cpp
index 673af46..eb0c380 100644
--- a/inst/cta/src/GCTAOnOffObservation.cpp
+++ b/inst/cta/src/GCTAOnOffObservation.cpp
@@ -1,7 +1,7 @@
 /***************************************************************************
  *          GCTAOnOffObservation.cpp - CTA on-off observation class        *
  * ----------------------------------------------------------------------- *
- *  copyright (C) 2014 by Chia-Chun Lu & Christoph Deil                    *
+ *  copyright (C) 2014-2016 by Chia-Chun Lu & Christoph Deil               *
  * ----------------------------------------------------------------------- *
  *                                                                         *
  *  This program is free software: you can redistribute it and/or modify   *
@@ -412,7 +412,7 @@ void GCTAOnOffObservation::write(GXmlElement& xml) const
 
 		// Handle effective area
 		else if (par->attribute("name") == "Arf") {
-			par->attribute("file", m_arf.filename());
+			par->attribute("file", m_arf.filename().url());
 			npar[4]++;
 		}
 
diff --git a/pyext/GApplicationPars.i b/pyext/GApplicationPars.i
index f1dae19..abf7792 100644
--- a/pyext/GApplicationPars.i
+++ b/pyext/GApplicationPars.i
@@ -1,7 +1,7 @@
 /***************************************************************************
  *           GApplicationPars.i - Application parameter container          *
  * ----------------------------------------------------------------------- *
- *  copyright (C) 2010-2015 by Juergen Knoedlseder                         *
+ *  copyright (C) 2010-2016 by Juergen Knoedlseder                         *
  * ----------------------------------------------------------------------- *
  *                                                                         *
  *  This program is free software: you can redistribute it and/or modify   *
@@ -27,6 +27,7 @@
 /* Put headers and other declarations here that are needed for compilation */
 #include "GApplicationPars.hpp"
 #include "GException.hpp"
+#include "GFilename.hpp"
 %}
 
 
@@ -40,8 +41,8 @@ class GApplicationPars : public GBase {
 public:
     // Constructors and destructors
     GApplicationPars(void);
-    explicit GApplicationPars(const std::string& filename);
-    GApplicationPars(const std::string& filename,
+    explicit GApplicationPars(const GFilename& filename);
+    GApplicationPars(const GFilename& filename,
                      const std::vector<std::string>& args);
     GApplicationPars(const GApplicationPars& pars);
     virtual ~GApplicationPars(void);
@@ -63,10 +64,10 @@ public:
     void              reserve(const int& num);
     void              extend(const GApplicationPars& pars);
     bool              contains(const std::string& name) const;
-    void              load(const std::string& filename);
-    void              load(const std::string& filename,
+    void              load(const GFilename& filename);
+    void              load(const GFilename& filename,
                            const std::vector<std::string>& args);
-    void              save(const std::string& filename);
+    void              save(const GFilename& filename);
 };
 
 
diff --git a/pyext/GArf.i b/pyext/GArf.i
index da3f803..c9476aa 100644
--- a/pyext/GArf.i
+++ b/pyext/GArf.i
@@ -1,7 +1,7 @@
 /***************************************************************************
  *               GArf.i - XSPEC Auxiliary Response File class              *
  * ----------------------------------------------------------------------- *
- *  copyright (C) 2013-2015 by Juergen Knoedlseder                         *
+ *  copyright (C) 2013-2016 by Juergen Knoedlseder                         *
  * ----------------------------------------------------------------------- *
  *                                                                         *
  *  This program is free software: you can redistribute it and/or modify   *
@@ -39,23 +39,25 @@ class GArf : public GBase {
 public:
     // Constructors and destructors
     GArf(void);
-    explicit GArf(const std::string& filename);
+    explicit GArf(const GFilename& filename);
     explicit GArf(const GEbounds& ebds);
     GArf(const GArf& arf);
     virtual ~GArf(void);
 
     // Methods
-    void            clear(void);
-    GArf*           clone(void) const;
-    std::string     classname(void) const;
-    int             size(void) const;
-    double&         at(const int& index);
-    const GEbounds& ebounds(void) const;
-    void            load(const std::string& filename);
-    void            save(const std::string& filename,
-                         const bool& clobber = false) const;
-    void            read(const GFitsTable& table);
-    void            write(GFits& fits) const;
+    void             clear(void);
+    GArf*            clone(void) const;
+    std::string      classname(void) const;
+    int              size(void) const;
+    double&          at(const int& index);
+    const double&    at(const int& index) const;
+    const GEbounds&  ebounds(void) const;
+    void             load(const GFilename& filename);
+    void             save(const GFilename& filename,
+                          const bool&      clobber = false) const;
+    void             read(const GFitsTable& table);
+    void             write(GFits& fits) const;
+    const GFilename& filename(void) const;
 };
 
 
diff --git a/pyext/GCsv.i b/pyext/GCsv.i
index 3a9645c..04cbfae 100644
--- a/pyext/GCsv.i
+++ b/pyext/GCsv.i
@@ -1,7 +1,7 @@
 /***************************************************************************
  *               GCsv.i - Comma-separated values table class               *
  * ----------------------------------------------------------------------- *
- *  copyright (C) 2010-2015 by Juergen Knoedlseder                         *
+ *  copyright (C) 2010-2016 by Juergen Knoedlseder                         *
  * ----------------------------------------------------------------------- *
  *                                                                         *
  *  This program is free software: you can redistribute it and/or modify   *
@@ -87,7 +87,7 @@ public:
     // Constructors and destructors
     GCsv(void);
     GCsv(const int& nrows, const int& ncols);
-    GCsv(const std::string& filename, const std::string& sep = " ");
+    GCsv(const GFilename& filename, const std::string& sep = " ");
     GCsv(const GCsv& csv);
     virtual ~GCsv(void);
  
@@ -106,8 +106,8 @@ public:
     void        string(const int& row, const int& col, const std::string& value);
     void        real(const int& row, const int& col, const double& value);
     void        integer(const int& row, const int& col, const int& value);
-    void        load(const std::string& filename, const std::string& sep = " ");
-    void        save(const std::string& filename, const std::string& sep = " ",
+    void        load(const GFilename& filename, const std::string& sep = " ");
+    void        save(const GFilename& filename, const std::string& sep = " ",
                      const bool& clobber = false) const;
 };
 
diff --git a/pyext/GFits.i b/pyext/GFits.i
index f952311..40b6685 100644
--- a/pyext/GFits.i
+++ b/pyext/GFits.i
@@ -53,7 +53,7 @@ class GFits : public GContainer {
 public:
     // Constructors and destructors
     GFits(void);
-    GFits(const std::string& filename, const bool& create = false);
+    GFits(const GFilename& filename, const bool& create = false);
     GFits(const GFits& fits);
     virtual ~GFits(void);
 
@@ -82,11 +82,11 @@ public:
     bool             contains(const std::string& extname) const;
     const GFilename& filename(void) const;
     int              extno(const std::string& extname) const;
-    void             open(const std::string& filename,
-                          const bool&        create = false);
+    void             open(const GFilename& filename,
+                          const bool&      create = false);
     void             save(const bool& clobber = false);
-    void             saveto(const std::string& filename,
-                            const bool&        clobber = false);
+    void             saveto(const GFilename& filename,
+                            const bool&      clobber = false);
     void             close(void);
 };
 
diff --git a/pyext/GLog.i b/pyext/GLog.i
index 3b73552..ae62837 100644
--- a/pyext/GLog.i
+++ b/pyext/GLog.i
@@ -1,7 +1,7 @@
 /***************************************************************************
  *                        GLog.i - Information logger                      *
  * ----------------------------------------------------------------------- *
- *  copyright (C) 2010-2015 by Juergen Knoedlseder                         *
+ *  copyright (C) 2010-2016 by Juergen Knoedlseder                         *
  * ----------------------------------------------------------------------- *
  *                                                                         *
  *  This program is free software: you can redistribute it and/or modify   *
@@ -39,7 +39,7 @@ class GLog {
 public:
     // Constructors and destructors
     GLog(void);
-    GLog(const std::string& filename, const bool& clobber = false);
+    GLog(const GFilename& filename, const bool& clobber = false);
     GLog(const GLog& log);
     virtual ~GLog(void);
 
@@ -47,7 +47,7 @@ public:
     void               clear(void);
     int                size(void) const;
     std::string        classname(void) const;
-    void               open(const std::string& filename, const bool& clobber = false);
+    void               open(const GFilename& filename, const bool& clobber = false);
     void               close(void);
     void               flush(const bool& force = false);
     void               date(const bool& flag);
@@ -68,7 +68,7 @@ public:
     const int&         max_size(void) const;
     const int&         indent(void) const;
     const GChatter&    chatter(void) const;
-    const std::string& filename(void) const;
+    const GFilename&   filename(void) const;
 };
 
 
diff --git a/pyext/GModelSpatialDiffuseCube.i b/pyext/GModelSpatialDiffuseCube.i
index 017b2b3..cfe3cc6 100644
--- a/pyext/GModelSpatialDiffuseCube.i
+++ b/pyext/GModelSpatialDiffuseCube.i
@@ -1,7 +1,7 @@
 /***************************************************************************
  *        GModelSpatialDiffuseCube.i - Spatial map cube model class        *
  * ----------------------------------------------------------------------- *
- *  copyright (C) 2011-2015 by Juergen Knoedlseder                         *
+ *  copyright (C) 2011-2016 by Juergen Knoedlseder                         *
  * ----------------------------------------------------------------------- *
  *                                                                         *
  *  This program is free software: you can redistribute it and/or modify   *
@@ -39,8 +39,8 @@ public:
     // Constructors and destructors
     GModelSpatialDiffuseCube(void);
     explicit GModelSpatialDiffuseCube(const GXmlElement& xml);
-    GModelSpatialDiffuseCube(const std::string& filename,
-                             const double&      value = 1.0);
+    GModelSpatialDiffuseCube(const GFilename& filename,
+                             const double&    value = 1.0);
     GModelSpatialDiffuseCube(const GSkyMap&   map,
                              const GEnergies& energies,
                              const double&    value = 1.0);
@@ -69,8 +69,8 @@ public:
     int                        pixels(void) const;
     double                     value(void) const;
     void                       value(const double& value);
-    const std::string&         filename(void) const;
-    void                       filename(const std::string& filename);
+    const GFilename&           filename(void) const;
+    void                       filename(const GFilename& filename);
     const GSkyMap&             cube(void) const;
     void                       cube(const GSkyMap& cube);
     GEnergies                  energies(void);
@@ -78,8 +78,8 @@ public:
     const GModelSpectralNodes& spectrum(void) const;
     void                       set_mc_cone(const GSkyDir& centre,
                                            const double&  radius) const;
-    void                       load(const std::string& filename);
-    void                       save(const std::string& filename,
+    void                       load(const GFilename& filename);
+    void                       save(const GFilename& filename,
                                     const bool& clobber = false) const;
     //void                       read(const GFits& file);
     void                       write(GFits& file) const;
diff --git a/pyext/GSkyMap.i b/pyext/GSkyMap.i
index 1922686..bf6d893 100644
--- a/pyext/GSkyMap.i
+++ b/pyext/GSkyMap.i
@@ -1,7 +1,7 @@
 /***************************************************************************
  *                         GSkyMap.i - Sky map class                       *
  * ----------------------------------------------------------------------- *
- *  copyright (C) 2010-2015 by Juergen Knoedlseder                         *
+ *  copyright (C) 2010-2016 by Juergen Knoedlseder                         *
  * ----------------------------------------------------------------------- *
  *                                                                         *
  *  This program is free software: you can redistribute it and/or modify   *
@@ -110,20 +110,20 @@ class GSkyMap : public GBase {
 public:
     // Constructors and destructors
     GSkyMap(void);
-    explicit GSkyMap(const std::string& filename);
-    explicit GSkyMap(const std::string& coords,
-                     const int&         nside,
-                     const std::string& order,
-                     const int&         nmaps = 1);
-    explicit GSkyMap(const std::string& wcs,
-                     const std::string& coords,
-                     const double&      x,
-                     const double&      y,
-                     const double&      dx,
-                     const double&      dy,
-                     const int&         nx,
-                     const int&         ny,
-                     const int&         nmaps = 1);
+    explicit GSkyMap(const GFilename& filename);
+    GSkyMap(const std::string& coords,
+            const int&         nside,
+            const std::string& order,
+            const int&         nmaps = 1);
+    GSkyMap(const std::string& wcs,
+            const std::string& coords,
+            const double&      x,
+            const double&      y,
+            const double&      dx,
+            const double&      dy,
+            const int&         nx,
+            const int&         ny,
+            const int&         nmaps = 1);
     GSkyMap(const GSkyMap& map);
     virtual ~GSkyMap(void);
 
@@ -168,8 +168,8 @@ public:
     const double*         pixels(void) const;
     GSkyMap               extract(const int& map, const int& nmaps = 1) const;
     void                  stack_maps(void);
-    void                  load(const std::string& filename);
-    void                  save(const std::string& filename, bool clobber = false) const;
+    void                  load(const GFilename& filename);
+    void                  save(const GFilename& filename, bool clobber = false) const;
     void                  read(const GFitsHDU& hdu);
     void                  write(GFits& file) const;
 };
diff --git a/src/app/GApplicationPars.cpp b/src/app/GApplicationPars.cpp
index 7effd5b..376a81b 100644
--- a/src/app/GApplicationPars.cpp
+++ b/src/app/GApplicationPars.cpp
@@ -1,7 +1,7 @@
 /***************************************************************************
  *               GApplicationPars.cpp - Application parameters             *
  * ----------------------------------------------------------------------- *
- *  copyright (C) 2010-2015 by Juergen Knoedlseder                         *
+ *  copyright (C) 2010-2016 by Juergen Knoedlseder                         *
  * ----------------------------------------------------------------------- *
  *                                                                         *
  *  This program is free software: you can redistribute it and/or modify   *
@@ -34,9 +34,10 @@
 #include <sys/stat.h>      // mkdir() function
 #include <cstdlib>         // std::getenv() function
 #include <cstdio>          // std::fopen(), etc. functions
-#include "GApplicationPars.hpp"
 #include "GTools.hpp"
 #include "GException.hpp"
+#include "GFilename.hpp"
+#include "GApplicationPars.hpp"
 
 /* __ Method name definitions ____________________________________________ */
 #define G_ACCESS                 "GApplicationPars::operator[](std::string&)"
@@ -49,10 +50,10 @@
 #define G_REMOVE1                            "GApplicationPars::remove(int&)"
 #define G_REMOVE2                    "GApplicationPars::remove(std::string&)"
 #define G_EXTEND                "GApplicationPars::extend(GApplicationPars&)"
-#define G_LOAD1                        "GApplicationPars::load(std::string&)"
-#define G_LOAD2                       "GApplicationPars::load(std::string&, "\
+#define G_LOAD1                          "GApplicationPars::load(GFilename&)"
+#define G_LOAD2                         "GApplicationPars::load(GFilename&, "\
                                                  "std::vector<std::string>&)"
-#define G_SAVE                         "GApplicationPars::save(std::string&)"
+#define G_SAVE                           "GApplicationPars::save(GFilename&)"
 #define G_OUTPATH                   "GApplicationPars::outpath(std::string&)"
 #define G_READ                         "GApplicationPars::read(std::string&)"
 #define G_WRITE                       "GApplicationPars::write(std::string&)"
@@ -91,7 +92,7 @@ GApplicationPars::GApplicationPars(void)
  *
  * @param[in] filename Parameter filename. 
  ***************************************************************************/
-GApplicationPars::GApplicationPars(const std::string& filename)
+GApplicationPars::GApplicationPars(const GFilename& filename)
 {
     // Initialise private members for clean destruction
     init_members();
@@ -109,7 +110,8 @@ GApplicationPars::GApplicationPars(const std::string& filename)
  * @param[in] filename Parameter filename. 
  * @param[in] args Command line arguments. 
  ***************************************************************************/
-GApplicationPars::GApplicationPars(const std::string& filename, const std::vector<std::string>& args)
+GApplicationPars::GApplicationPars(const GFilename&                filename,
+                                   const std::vector<std::string>& args)
 {
     // Initialise private members for clean destruction
     init_members();
@@ -631,15 +633,15 @@ bool GApplicationPars::contains(const std::string& name) const
  *
  * Loads all parameters from parameter file.
  ***************************************************************************/
-void GApplicationPars::load(const std::string& filename)
+void GApplicationPars::load(const GFilename& filename)
 {
     // Reset parameters
     m_parfile.clear();
 
     // Get path to parameter file for input
-    std::string path = inpath(filename);
+    std::string path = inpath(filename.url());
     if (path.length() == 0) {
-        throw GException::par_file_not_found(G_LOAD1, filename);
+        throw GException::par_file_not_found(G_LOAD1, filename.url());
     }
 
     // Read parfile
@@ -667,16 +669,16 @@ void GApplicationPars::load(const std::string& filename)
  * Loads all parameters from parameter file. Parameters are overwritten by
  * the values specified in the command line arguments.
  ***************************************************************************/
-void GApplicationPars::load(const std::string& filename,
-                 const std::vector<std::string>& args)
+void GApplicationPars::load(const GFilename&                filename,
+                            const std::vector<std::string>& args)
 {
     // Reset parameters
     m_parfile.clear();
 
     // Get path to parameter file for input
-    std::string path = inpath(filename);
+    std::string path = inpath(filename.url());
     if (path.length() == 0) {
-        throw GException::par_file_not_found(G_LOAD2, filename);
+        throw GException::par_file_not_found(G_LOAD2, filename.url());
     }
 
     // Read parfile
@@ -741,12 +743,12 @@ void GApplicationPars::load(const std::string& filename,
  * @exception GException::par_file_not_found
  *            No valid directory to write the parameter file has been found.
  ***************************************************************************/
-void GApplicationPars::save(const std::string& filename)
+void GApplicationPars::save(const GFilename& filename)
 {
     // Get path to parameter file for output
-    std::string path = outpath(filename);
+    std::string path = outpath(filename.url());
     if (path.size() == 0) {
-        throw GException::par_file_not_found(G_SAVE, filename);
+        throw GException::par_file_not_found(G_SAVE, filename.url());
     }
 
     // Update parameter file
diff --git a/src/app/GLog.cpp b/src/app/GLog.cpp
index 98acc47..3cf5d31 100644
--- a/src/app/GLog.cpp
+++ b/src/app/GLog.cpp
@@ -1,7 +1,7 @@
 /***************************************************************************
  *                       GLog.cpp - Information logger                     *
  * ----------------------------------------------------------------------- *
- *  copyright (C) 2010-2014 by Juergen Knoedlseder                         *
+ *  copyright (C) 2010-2016 by Juergen Knoedlseder                         *
  * ----------------------------------------------------------------------- *
  *                                                                         *
  *  This program is free software: you can redistribute it and/or modify   *
@@ -75,7 +75,7 @@ GLog::GLog(void)
  *
  * Construct a logger with an open log file.
  ***************************************************************************/
-GLog::GLog(const std::string& filename, const bool& clobber)
+GLog::GLog(const GFilename& filename, const bool& clobber)
 {
     // Initialise private members for clean destruction
     init_members();
@@ -212,13 +212,13 @@ GLog& GLog::operator<<(GLog& log)
         log.flush(true);
 
         // Get the filename
-        std::string filename = log.filename();
+        GFilename filename = log.filename();
 
         // Close log's file
         log.close();
 
         // Open log's file in read mode
-        std::ifstream file(filename.c_str(), std::ios::in);
+        std::ifstream file(filename.url().c_str(), std::ios::in);
         if (file) {
 
             // Append all lines from file to this buffer
@@ -232,7 +232,7 @@ GLog& GLog::operator<<(GLog& log)
         }
 
         // Open log's file in append mode
-        log.open(filename,false);
+        log.open(filename, false);
     }
 
     // Flush
@@ -477,7 +477,7 @@ int GLog::size(void) const
  * Opens a file for logging. If a log file was already open it is closed
  * before opening a new file.
  ***************************************************************************/
-void GLog::open(const std::string& filename, const bool& clobber)
+void GLog::open(const GFilename& filename, const bool& clobber)
 {
     // Store the filename
     m_filename = filename;
@@ -487,10 +487,10 @@ void GLog::open(const std::string& filename, const bool& clobber)
 
     // Open file
     if (clobber) {
-        m_file = std::fopen(filename.c_str(), "w");
+        m_file = std::fopen(filename.url().c_str(), "w");
     }
     else {
-        m_file = std::fopen(filename.c_str(), "a");
+        m_file = std::fopen(filename.url().c_str(), "a");
     }
 
     // Return
diff --git a/src/fits/GFits.cpp b/src/fits/GFits.cpp
index c0e7fcf..7d4da74 100644
--- a/src/fits/GFits.cpp
+++ b/src/fits/GFits.cpp
@@ -80,6 +80,8 @@
 
 /***********************************************************************//**
  * @brief Void constructor
+ *
+ * Constructs empty FITS file.
  ***************************************************************************/
 GFits::GFits(void)
 {
@@ -100,7 +102,7 @@ GFits::GFits(void)
  * Construct an object by opening a FITS file. If the file does not exist it
  * will be created if @p create is set to true.
  ***************************************************************************/
-GFits::GFits(const std::string& filename, const bool& create)
+GFits::GFits(const GFilename& filename, const bool& create)
 {
     // Initialise class members
     init_members();
@@ -1009,23 +1011,23 @@ int GFits::extno(const std::string& extname) const
  * hdu(int extno) method.
  * Any environment variable present in the filename will be expanded.
  ***************************************************************************/
-void GFits::open(const std::string& filename, const bool& create)
+void GFits::open(const GFilename& filename, const bool& create)
 {
     // Remove any HDUs
     m_hdu.clear();
 
     // Expand environment variables
-    std::string fname(gammalib::expand_env(filename));
+    std::string fname(gammalib::expand_env(filename()));
 
     // Don't allow opening if a file is already open
     if (m_fitsfile != NULL) {
         std::string msg;
-        if (m_filename.filename() == GFilename(fname).filename()) {
-            msg = "FITS file \""+m_filename.filename()+"\" has already been "
+        if (m_filename.url() == GFilename(fname).url()) {
+            msg = "FITS file \""+m_filename.url()+"\" has already been "
                   "opened, cannot open it again.";
         }
         else {
-            msg = "A FITS file \""+m_filename.filename()+"\" has already "
+            msg = "A FITS file \""+m_filename.url()+"\" has already "
                   "been opened, cannot open another FITS file \""+
                   fname+"\" before closing the existing one.";
         }
@@ -1146,7 +1148,7 @@ void GFits::save(const bool& clobber)
     // If we attempt to save an existing file without overwriting permission
     // then throw an error
     if (!m_created && !clobber) {
-        throw GException::fits_file_exist(G_SAVE, m_filename.filename());
+        throw GException::fits_file_exist(G_SAVE, m_filename.url());
     }
 
     // If no FITS file has been opened then throw an error
@@ -1223,10 +1225,10 @@ void GFits::save(const bool& clobber)
  * Saves object into a specific FITS file.
  * Any environment variable present in the filename will be expanded.
  ***************************************************************************/
-void GFits::saveto(const std::string& filename, const bool& clobber)
+void GFits::saveto(const GFilename& filename, const bool& clobber)
 {
     // Expand environment variables
-    std::string fname = gammalib::expand_env(filename);
+    std::string fname = gammalib::expand_env(filename());
 
     // Create gzipped file name version
     std::string gzfname = fname + ".gz";
@@ -1320,7 +1322,7 @@ std::string GFits::print(const GChatter& chatter) const
 
         // Append file information
         result.append("\n"+gammalib::parformat("Filename"));
-        result.append(m_filename.filename());
+        result.append(m_filename.url());
         result.append("\n"+gammalib::parformat("History"));
         if (m_created) {
             result.append("new file");
diff --git a/src/model/GModelSpatialDiffuseCube.cpp b/src/model/GModelSpatialDiffuseCube.cpp
index c9c19bb..f500ab6 100644
--- a/src/model/GModelSpatialDiffuseCube.cpp
+++ b/src/model/GModelSpatialDiffuseCube.cpp
@@ -1,7 +1,7 @@
 /***************************************************************************
  *       GModelSpatialDiffuseCube.cpp - Spatial map cube model class       *
  * ----------------------------------------------------------------------- *
- *  copyright (C) 2010-2015 by Juergen Knoedlseder                         *
+ *  copyright (C) 2010-2016 by Juergen Knoedlseder                         *
  * ----------------------------------------------------------------------- *
  *                                                                         *
  *  This program is free software: you can redistribute it and/or modify   *
@@ -51,7 +51,7 @@ const GModelSpatialRegistry    g_spatial_cube_registry(&g_spatial_cube_seed);
 #define G_READ                 "GModelSpatialDiffuseCube::read(GXmlElement&)"
 #define G_WRITE               "GModelSpatialDiffuseCube::write(GXmlElement&)"
 #define G_ENERGIES           "GModelSpatialDiffuseCube::energies(GEnergies&)"
-#define G_LOAD_CUBE                   "GModelSpatialDiffuseCube::load_cube()"
+#define G_LOAD_CUBE         "GModelSpatialDiffuseCube::load_cube(GFilename&)"
 
 /* __ Macros _____________________________________________________________ */
 
@@ -113,8 +113,8 @@ GModelSpatialDiffuseCube::GModelSpatialDiffuseCube(const GXmlElement& xml) :
  * Constructs map cube model by loading a map cube from @p filename and by
  * assigning the normalization @p value.
  ***************************************************************************/
-GModelSpatialDiffuseCube::GModelSpatialDiffuseCube(const std::string& filename,
-                                                   const double&      value) :
+GModelSpatialDiffuseCube::GModelSpatialDiffuseCube(const GFilename& filename,
+                                                   const double&    value) :
                           GModelSpatialDiffuse()
 {
     // Initialise members
@@ -649,7 +649,7 @@ void GModelSpatialDiffuseCube::write(GXmlElement& xml) const
     }
 
     // Set filename
-    xml.attribute("file", m_filename);
+    xml.attribute("file", m_filename.url());
 
     // Return
     return;
@@ -975,7 +975,7 @@ void GModelSpatialDiffuseCube::set_mc_cone(const GSkyDir& centre,
  *
  * Loads cube into the model class.
  ***************************************************************************/
-void GModelSpatialDiffuseCube::load(const std::string& filename)
+void GModelSpatialDiffuseCube::load(const GFilename& filename)
 {
     // Load cube
     load_cube(filename);
@@ -992,12 +992,12 @@ void GModelSpatialDiffuseCube::load(const std::string& filename)
  * @brief Save cube into FITS file
  *
  * @param[in] filename Cube FITS file name.
- * @param[in] clobber Overwrite existing FITS file (default=false).
+ * @param[in] clobber Overwrite existing FITS file (default: false).
  *
  * Saves spatial cube model into a FITS file.
  ***************************************************************************/
-void GModelSpatialDiffuseCube::save(const std::string& filename,
-                                    const bool&        clobber) const
+void GModelSpatialDiffuseCube::save(const GFilename& filename,
+                                    const bool&      clobber) const
 {
     // Create empty FITS file
     GFits fits;
@@ -1056,7 +1056,8 @@ std::string GModelSpatialDiffuseCube::print(const GChatter& chatter) const
         result.append("=== GModelSpatialDiffuseCube ===");
 
         // Append parameters
-        result.append("\n"+gammalib::parformat("Map cube file")+m_filename);
+        result.append("\n"+gammalib::parformat("Map cube file"));
+        result.append(m_filename.url());
         if (m_loaded) {
             result.append(" [loaded]");
         }
@@ -1210,7 +1211,7 @@ void GModelSpatialDiffuseCube::free_members(void)
 void GModelSpatialDiffuseCube::fetch_cube(void) const
 {
     // Load cube if it is not yet loaded
-    if (!m_loaded && !m_filename.empty()) {
+    if (!m_loaded && !m_filename.is_empty()) {
 
         // Put in a OMP critical zone
         #pragma omp critical
@@ -1235,7 +1236,7 @@ void GModelSpatialDiffuseCube::fetch_cube(void) const
  *
  * Load diffuse cube.
  ***************************************************************************/
-void GModelSpatialDiffuseCube::load_cube(const std::string& filename)
+void GModelSpatialDiffuseCube::load_cube(const GFilename& filename)
 {
     // Initialise skymap
     m_cube.clear();
@@ -1248,13 +1249,14 @@ void GModelSpatialDiffuseCube::load_cube(const std::string& filename)
     m_filename = filename;
 
     // Get expanded filename
-    std::string fname = gammalib::expand_env(filename);
+    //std::string fname = gammalib::expand_env(filename);
 
     // Load cube
-    m_cube.load(fname);
+    //m_cube.load(fname);
+    m_cube.load(filename);
 
     // Load energies
-    GEnergies energies(fname);
+    GEnergies energies(filename);
 
     // Extract number of energy bins
     int num = energies.size();
diff --git a/src/sky/GSkyMap.cpp b/src/sky/GSkyMap.cpp
index edd9ed9..bd83ef7 100644
--- a/src/sky/GSkyMap.cpp
+++ b/src/sky/GSkyMap.cpp
@@ -1,7 +1,7 @@
 /***************************************************************************
  *                       GSkyMap.cpp - Sky map class                       *
  * ----------------------------------------------------------------------- *
- *  copyright (C) 2010-2015 by Juergen Knoedlseder                         *
+ *  copyright (C) 2010-2016 by Juergen Knoedlseder                         *
  * ----------------------------------------------------------------------- *
  *                                                                         *
  *  This program is free software: you can redistribute it and/or modify   *
@@ -31,13 +31,18 @@
 #include "GException.hpp"
 #include "GMath.hpp"
 #include "GTools.hpp"
+#include "GFits.hpp"
+#include "GFitsTable.hpp"
+#include "GFitsBinTable.hpp"
+#include "GFitsImage.hpp"
+#include "GFitsImageDouble.hpp"
+#include "GFitsTableDoubleCol.hpp"
 #include "GSkyMap.hpp"
 #include "GHealpix.hpp"
 #include "GWcsRegistry.hpp"
 #include "GWcs.hpp"
-#include "GFits.hpp"
-#include "GFitsTableDoubleCol.hpp"
-#include "GFitsImageDouble.hpp"
+#include "GMatrix.hpp"
+#include "GVector.hpp"
 
 /* __ Method name definitions ____________________________________________ */
 #define G_CONSTRUCT_HPX                "GSkyMap::GSkyMap(std::string&, int&,"\
@@ -105,7 +110,7 @@ GSkyMap::GSkyMap(void)
  *
  * @param[in] filename FITS file name.
  ***************************************************************************/
-GSkyMap::GSkyMap(const std::string& filename)
+GSkyMap::GSkyMap(const GFilename& filename)
 {
     // Initialise class members for clean destruction
     init_members();
@@ -1739,7 +1744,7 @@ void GSkyMap::stack_maps(void)
  * @todo Do we have to restrict a HEALPix map to a BinTable and a WCS map
  * to a Double precision image???
  ***************************************************************************/
-void GSkyMap::load(const std::string& filename)
+void GSkyMap::load(const GFilename& filename)
 {
     // Free memory and initialise members
     free_members();
@@ -1808,7 +1813,7 @@ void GSkyMap::load(const std::string& filename)
  *
  * The method does nothing if the skymap holds no valid WCS.
  ***************************************************************************/
-void GSkyMap::save(const std::string& filename, bool clobber) const
+void GSkyMap::save(const GFilename& filename, bool clobber) const
 {
     // Continue only if we have data to save
     if (m_proj != NULL) {
diff --git a/src/support/GCsv.cpp b/src/support/GCsv.cpp
index 0c3c13a..7134224 100644
--- a/src/support/GCsv.cpp
+++ b/src/support/GCsv.cpp
@@ -1,7 +1,7 @@
 /***************************************************************************
  *              GCsv.cpp - Comma-separated values table class              *
  * ----------------------------------------------------------------------- *
- *  copyright (C) 2010-2015 by Juergen Knoedlseder                         *
+ *  copyright (C) 2010-2016 by Juergen Knoedlseder                         *
  * ----------------------------------------------------------------------- *
  *                                                                         *
  *  This program is free software: you can redistribute it and/or modify   *
@@ -31,12 +31,13 @@
 #include <cstdio>            // std::fopen, std::fgets, std::fclose, etc...
 #include "GCsv.hpp"
 #include "GTools.hpp"
+#include "GFilename.hpp"
 #include "GException.hpp"
 
 /* __ Method name definitions ____________________________________________ */
 #define G_ACCESS                               "GCsv::operator()(int&, int&)"
-#define G_LOAD                       "GCsv::load(std::string&, std::string&)"
-#define G_SAVE                "GCsv::save(std::string&, std::string&, bool&)"
+#define G_LOAD                         "GCsv::load(GFilename&, std::string&)"
+#define G_SAVE                  "GCsv::save(GFilename&, std::string&, bool&)"
 
 /* __ Macros _____________________________________________________________ */
 
@@ -96,7 +97,7 @@ GCsv::GCsv(const int& nrows, const int& ncols)
  * @param[in] filename Filename.
  * @param[in] sep Column separator (default is whitespace).
  ***************************************************************************/
-GCsv::GCsv(const std::string& filename, const std::string& sep)
+GCsv::GCsv(const GFilename& filename, const std::string& sep)
 { 
     // Initialise private
     init_members();
@@ -370,7 +371,7 @@ void GCsv::integer(const int& row, const int& col, const int& value)
  * Load CSV table from ASCII file. Any environment variable present in the
  * filename will be expanded.
  **************************************************************************/
-void GCsv::load(const std::string& filename, const std::string& sep)
+void GCsv::load(const GFilename& filename, const std::string& sep)
 {
     // Clear instance
     clear();
@@ -380,7 +381,7 @@ void GCsv::load(const std::string& filename, const std::string& sep)
     char  line[n];
 
     // Expand environment variables
-    std::string fname = gammalib::expand_env(filename);
+    std::string fname = gammalib::expand_env(filename.url());
 
     // Open CSV table (read-only)
     FILE* fptr = std::fopen(fname.c_str(), "r");
@@ -456,25 +457,26 @@ void GCsv::load(const std::string& filename, const std::string& sep)
  * Save CSV table into ASCII file. Any environment variable present in the
  * filename will be expanded.
  **************************************************************************/
-void GCsv::save(const std::string& filename, const std::string& sep,
-                const bool& clobber) const
+void GCsv::save(const GFilename&   filename,
+                const std::string& sep,
+                const bool&        clobber) const
 {
     // Throw exception if file exists but clobber flag is false
-    if (!clobber && gammalib::file_exists(filename)) {
-        std::string msg = "File \""+filename+"\" exists already but the "
-                          "clobber flag is set to \"false\". Set the "
+    if (!clobber && gammalib::file_exists(filename.url())) {
+        std::string msg = "File \""+filename.url()+"\" exists already but "
+                          "the clobber flag is set to \"false\". Set the "
                           "clobber flag to true to overwrite the existing "
                           "file or specify another file name.";
         throw GException::invalid_value(G_SAVE, msg);
     }
 
     // Expand environment variables
-    std::string fname = gammalib::expand_env(filename);
+    std::string fname = gammalib::expand_env(filename.url());
 
     // Open CSV table (write-only)
     FILE* fptr = std::fopen(fname.c_str(), "w");
     if (fptr == NULL) {
-        std::string msg = "Unable to create file \""+filename+"\".";
+        std::string msg = "Unable to create file \""+filename.url()+"\".";
         throw GException::file_error(G_SAVE, msg);
     }
 
diff --git a/src/xspec/GArf.cpp b/src/xspec/GArf.cpp
index e371920..cd311ba 100644
--- a/src/xspec/GArf.cpp
+++ b/src/xspec/GArf.cpp
@@ -1,7 +1,7 @@
 /***************************************************************************
  *               GArf.cpp - XSPEC Auxiliary Response File class            *
  * ----------------------------------------------------------------------- *
- *  copyright (C) 2013 by Juergen Knoedlseder                              *
+ *  copyright (C) 2013-2016 by Juergen Knoedlseder                         *
  * ----------------------------------------------------------------------- *
  *                                                                         *
  *  This program is free software: you can redistribute it and/or modify   *
@@ -30,7 +30,10 @@
 #endif
 #include "GArf.hpp"
 #include "GException.hpp"
+#include "GFilename.hpp"
 #include "GTools.hpp"
+#include "GFits.hpp"
+#include "GFitsTable.hpp"
 #include "GFitsBinTable.hpp"
 #include "GFitsTableShortCol.hpp"
 #include "GFitsTableFloatCol.hpp"
@@ -69,7 +72,7 @@ GArf::GArf(void)
  *
  * @param[in] filename File name.
  ***************************************************************************/
-GArf::GArf(const std::string& filename)
+GArf::GArf(const GFilename& filename)
 {
     // Initialise members
     init_members();
@@ -250,7 +253,7 @@ const double& GArf::at(const int& index) const
  *
  * @param[in] filename File name.
  ***************************************************************************/
-void GArf::load(const std::string& filename)
+void GArf::load(const GFilename& filename)
 {
     // Clear any existing models
     clear();
@@ -279,9 +282,9 @@ void GArf::load(const std::string& filename)
  * @brief Save Auxiliary Response File
  *
  * @param[in] filename File name.
- * @param[in] clobber Overwrite existing file? (defaults to true)
+ * @param[in] clobber Overwrite existing file? (defaults: false)
  ***************************************************************************/
-void GArf::save(const std::string& filename, const bool& clobber) const
+void GArf::save(const GFilename& filename, const bool& clobber) const
 {
     // Open FITS file
     GFits fits;
diff --git a/test/test_GModel.cpp b/test/test_GModel.cpp
index cdbfe94..bbddf81 100644
--- a/test/test_GModel.cpp
+++ b/test/test_GModel.cpp
@@ -1,7 +1,7 @@
 /***************************************************************************
  *                   test_GModel.cpp - test GModel class                   *
  * ----------------------------------------------------------------------- *
- *  copyright (C) 2009-2015 by Juergen Knoedlseder                         *
+ *  copyright (C) 2009-2016 by Juergen Knoedlseder                         *
  * ----------------------------------------------------------------------- *
  *                                                                         *
  *  This program is free software: you can redistribute it and/or modify   *
@@ -584,7 +584,7 @@ void TestGModel::test_diffuse_cube(void)
         GModelSpatialDiffuseCube model;
         test_assert(model.type() == "MapCubeFunction",
                                     "Model type \"MapCubeFunction\" expected.");
-        test_assert(model.filename() == "", "Model filename \"\" expected.");
+        test_assert(model.filename().url() == "", "Model filename \"\" expected.");
         test_try_success();
     }
     catch (std::exception &e) {
@@ -596,7 +596,8 @@ void TestGModel::test_diffuse_cube(void)
     try {
         GModelSpatialDiffuseCube model(m_cube_file, 3.0);
         test_value(model.value(), 3.0);
-        test_assert(model.filename() == m_cube_file, "Expected \""+m_cube_file+"\"");
+        test_assert(model.filename().url() == m_cube_file,
+                    "Expected \""+m_cube_file+"\"");
         test_try_success();
     }
     catch (std::exception &e) {
@@ -613,7 +614,7 @@ void TestGModel::test_diffuse_cube(void)
         }
         GModelSpatialDiffuseCube model(map, energies, 3.0);
         test_value(model.value(), 3.0);
-        test_assert(model.filename() == "", "Expected \"\"");
+        test_assert(model.filename().url() == "", "Expected \"\"");
         //test_assert(model.cube() == map, "Map cube is not the expected one");
         test_try_success();
     }
@@ -631,8 +632,8 @@ void TestGModel::test_diffuse_cube(void)
         test_value(model.size(), 1);
         test_assert(model.type() == "MapCubeFunction", "Expected \"MapCubeFunction\"");
         test_value(model.value(), 1.0);
-        test_assert(model.filename() == m_cube_file,
-                                        "Model filename \""+m_cube_file+"\" expected.");
+        test_assert(model.filename().url() == m_cube_file,
+                    "Model filename \""+m_cube_file+"\" expected.");
 
         // Test value method
         model.value(3.9);
@@ -640,8 +641,8 @@ void TestGModel::test_diffuse_cube(void)
 
         // Test filename method
         model.filename("Help me!");
-        test_assert(model.filename() == "Help me!",
-                                        "Model filename \"Help me!\" expected.");
+        test_assert(model.filename().url() == "Help me!",
+                    "Model filename \"Help me!\" expected.");
 
         // Test cube method
         model.cube(GSkyMap("GAL", 16, "RING", 10));
diff --git a/test/test_GXspec.cpp b/test/test_GXspec.cpp
index 13278d9..e95cd3b 100644
--- a/test/test_GXspec.cpp
+++ b/test/test_GXspec.cpp
@@ -1,7 +1,7 @@
 /***************************************************************************
  *                  test_GXspec.hpp - Test Xspec module                    *
  * ----------------------------------------------------------------------- *
- *  copyright (C) 2013 by Juergen Knoedlseder                              *
+ *  copyright (C) 2013-2016 by Juergen Knoedlseder                         *
  * ----------------------------------------------------------------------- *
  *                                                                         *
  *  This program is free software: you can redistribute it and/or modify   *
@@ -210,11 +210,11 @@ void TestGXspec::test_GArf(void)
 
     // Test saving and loading
     arf.save("arf.fits", true);
-    test_assert(arf.filename() == "arf.fits",
-                "Unexpected filename \""+arf.filename()+"\".");
+    test_assert(arf.filename().url() == "arf.fits",
+                "Unexpected filename \""+arf.filename().url()+"\".");
     arf.load("arf.fits");
-    test_assert(arf.filename() == "arf.fits",
-                "Unexpected filename \""+arf.filename()+"\".");
+    test_assert(arf.filename().url() == "arf.fits",
+                "Unexpected filename \""+arf.filename().url()+"\".");
     test_value(arf[0], 5.0, 1.0e-6);
     test_value(arf[1], 3.7, 1.0e-6);
     for (int i = 2; i < 9; i += 2) {
@@ -228,8 +228,8 @@ void TestGXspec::test_GArf(void)
 
     // Test constructing
     GArf arf2("arf.fits");
-    test_assert(arf2.filename() == "arf.fits",
-                "Unexpected filename \""+arf2.filename()+"\".");
+    test_assert(arf2.filename().url() == "arf.fits",
+                "Unexpected filename \""+arf2.filename().url()+"\".");
     test_value(arf2[0], 5.0, 1.0e-6);
     test_value(arf2[1], 3.7, 1.0e-6);
     for (int i = 2; i < 9; i += 2) {