From 26ff15609d6215c9f8d2425f8f01beb77a2b18fe Mon Sep 17 00:00:00 2001
From: knodlseder <>
Date: Sat, 1 Mar 2008 01:08:26 +0000
Subject: [PATCH] implement LAT PSF get dummy

---
 include/GLATResponse.hpp |  1 +
 src/rsp/GLATResponse.cpp | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 35 insertions(+), 0 deletions(-)

diff --git a/include/GLATResponse.hpp b/include/GLATResponse.hpp
index 19b08d4..dd4ef56 100644
--- a/include/GLATResponse.hpp
+++ b/include/GLATResponse.hpp
@@ -78,6 +78,7 @@ private:
 
     // Private PSF methods
     void    psf_init(void);
+    double  psf_get(const double& delta, const double& logE, const double& ctheta);
     double  psf_scale(const double& energy);
     double  psf_base_value(const double& u, const double& gamma);
     GVector psf_base_vector(const GVector& u, const double& gamma);
diff --git a/src/rsp/GLATResponse.cpp b/src/rsp/GLATResponse.cpp
index 63d0404..ce7a9af 100644
--- a/src/rsp/GLATResponse.cpp
+++ b/src/rsp/GLATResponse.cpp
@@ -424,6 +424,40 @@ void GLATResponse::psf_init(void)
 
 
 /***************************************************************************
+ *                              Get PSF value                              *
+ * ----------------------------------------------------------------------- *
+ ***************************************************************************/
+/// Returns the GLAST LAT PSF value
+/// @param delta angular separation between true and observed photon direction
+/// @param logE logarithm of the true photon energy
+/// @param ctheta cosine of the zenith angle with respect to the pointing axis
+double GLATResponse::psf_get(const double& delta, const double& logE, const double& ctheta)
+{
+    // Interpolate sigma and norm tables
+    double sigma = 1.0;  // Perform bi-linear interpolation in logE and ctheta
+    double norm  = 1.0;  // Perform bi-linear interpolation in logE and ctheta
+    
+    // Evaluate scale
+    double energy = pow(10.0,logE);    // DUMMY: t=(0.01*(10.0^logE))^-0.8
+    double scale  = psf_scale(energy);
+    
+    // Get stretch factor
+    double stretch = sigma * scale;
+    
+    // Get PSF value from table
+    double r   = delta * deg2rad / stretch;  // in radians
+    int    inx = (r - m_psf_angle_min) / m_psf_angle_bin;  // Perform linear interpolation
+    double psf = 1.0;
+    
+    // Normalize PSF
+    psf *= norm;
+    
+    // Return PSF value
+    return psf;
+}
+
+
+/***************************************************************************
  *                            Returns PSF scale                            *
  * ----------------------------------------------------------------------- *
  ***************************************************************************/
--
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