From 095213539bf55ec1a9e6f7f93ae6c012139dbd80 Mon Sep 17 00:00:00 2001
From: Craig Warren <craig_warren@me.com>
Date: Thu, 7 Apr 2016 15:40:49 +0100
Subject: [PATCH] Updated dispersion check function to return the spatial
 resolution of the minimum wavelength in the model.

---
 gprMax/grid.py | 23 +++++++++++------------
 1 file changed, 11 insertions(+), 12 deletions(-)

diff --git a/gprMax/grid.py b/gprMax/grid.py
index 6a82f712..365b2d08 100644
--- a/gprMax/grid.py
+++ b/gprMax/grid.py
@@ -99,9 +99,12 @@ def dispersion_check(G):
         G (class): Grid class instance - holds essential parameters describing the model.
     
     Returns:
-        (boolean): Potential numerical dispersion
+        resolution (float): Potential numerical dispersion
     """
     
+    # Minimum number of spatial steps to resolve smallest wavelength
+    resolvedsteps = 10
+    
     # Find maximum frequency
     maxfreqs = []
     for waveform in G.waveforms:
@@ -137,25 +140,21 @@ def dispersion_check(G):
         
         # Find minimum wavelength
         ers = [material.er for material in G.materials]
-        miner = max(ers)
+        maxer = max(ers)
 
         # Minimum velocity
-        minvelocity = c / np.sqrt(miner)
-
-        # Minimum number of spatial steps to resolve smallest wavelength
-        resolution = 10
+        minvelocity = c / np.sqrt(maxer)
         
         # Minimum wavelength
         minwavelength = minvelocity / maxfreq
         
-        # Test for numerical dispersion
-        if max((G.dx, G.dy, G.dz)) > (minwavelength / resolution):
-            return True
-        else:
-            return False
+        # Resolution of minimum wavelength
+        resolution = minwavelength / resolvedsteps
 
     else:
-        return False
+        resolution = 0
+
+    return resolution
 
 
 def get_other_directions(direction):