diff -r 44897b1ba4e2 -r 15b51d278bf0 gui/mapstorage.cc
--- a/gui/mapstorage.cc	Wed Jul 27 11:19:35 2005 +0000
+++ b/gui/mapstorage.cc	Wed Jul 27 11:35:13 2005 +0000
@@ -6,14 +6,22 @@
 
 int MapStorage::addNodeMap(const std::string & name, Graph::NodeMap<double> *nodemap)
 {
-  nodemap_storage[name]=nodemap;
-  return 0;
+  if( nodemap_storage.find(name) == nodemap_storage.end() )
+    {
+      nodemap_storage[name]=nodemap;
+      return 0;
+    }
+  return 1;
 }
 
 int MapStorage::addEdgeMap(const std::string & name, Graph::EdgeMap<double> *edgemap)
 {
-  edgemap_storage[name]=edgemap;
-  return 0;
+  if( edgemap_storage.find(name) == edgemap_storage.end() )
+    {
+      edgemap_storage[name]=edgemap;
+      return 0;
+    }
+  return 1;
 }
 
 double MapStorage::maxOfNodeMap(const std::string & name)