From d9c04c5472048d3b2eeef41df0905d5fd5edb08d Mon Sep 17 00:00:00 2001
From: Joe Taylor <k1jt@arrl.org>
Date: Wed, 27 Apr 2016 17:03:24 +0000
Subject: [PATCH] Fix a bug in azdist() that can cause bad behavior when
 computed distance is 0.

git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@6650 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
---
 lib/azdist.f90 | 22 ++++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/lib/azdist.f90 b/lib/azdist.f90
index 528801f47..dd2c51a86 100644
--- a/lib/azdist.f90
+++ b/lib/azdist.f90
@@ -1,5 +1,6 @@
-subroutine azdist(MyGrid,HisGrid,utch,nAz,nEl,nDmiles,nDkm,nHotAz,nHotABetter)
+subroutine azdist(grid1,grid2,utch,nAz,nEl,nDmiles,nDkm,nHotAz,nHotABetter)
 
+  character*(*) grid1,grid2
   character*6 MyGrid,HisGrid,mygrid0,hisgrid0
   real*8 utch,utch0
   logical HotABetter,IamEast
@@ -11,6 +12,11 @@ subroutine azdist(MyGrid,HisGrid,utch,nAz,nEl,nDmiles,nDkm,nHotAz,nHotABetter)
   data mygrid0/"      "/,hisgrid0/"      "/,utch0/-999.d0/
   save
 
+  MyGrid=grid1
+  HisGrid=grid2
+  if(ichar(grid1(5:5)).eq.0) MyGrid(5:6)='  '
+  if(ichar(grid2(5:5)).eq.0) HisGrid(5:6)='  '
+
   if(MyGrid.eq.HisGrid) then
      naz=0
      nel=0
@@ -46,7 +52,19 @@ subroutine azdist(MyGrid,HisGrid,utch,nAz,nEl,nDmiles,nDkm,nHotAz,nHotABetter)
 
   call grid2deg(MyGrid,dlong1,dlat1)
   call grid2deg(HisGrid,dlong2,dlat2)
-  call geodist(dlat1,dlong1,dlat2,dlong2,Az,Baz,Dkm)
+  eps=1.e-6
+  if(abs(dlat1-dlat2).lt.eps .and. abs(dling1-dling2).lt.eps) then
+     Az=0.
+     Dmiles=0.
+     Dkm=0.0
+     El=0.
+     HotA=0.
+     HotB=0.
+     HotABetter=.true.
+     go to 900
+  else
+     call geodist(dlat1,dlong1,dlat2,dlong2,Az,Baz,Dkm)
+  endif
 
   ndkm=Dkm/100
   j=ndkm-4