Index: /issm/trunk-jpl/src/m/classes/geometry.m
===================================================================
--- /issm/trunk-jpl/src/m/classes/geometry.m	(revision 19572)
+++ /issm/trunk-jpl/src/m/classes/geometry.m	(revision 19573)
@@ -70,5 +70,5 @@
 				md = checkfield(md,'fieldname','geometry.base'      ,'NaN',1,'size',[md.mesh.numberofvertices 1]);
 				md = checkfield(md,'fieldname','geometry.thickness','NaN',1,'size',[md.mesh.numberofvertices 1],'>',0);
-				if any((self.thickness-self.surface+self.base)>10^-9),
+				if any(abs(self.thickness-self.surface+self.base)>10^-9),
 					md = checkmessage(md,['equality thickness=surface-base violated']);
 				end 
Index: /issm/trunk-jpl/src/m/classes/geometry.py
===================================================================
--- /issm/trunk-jpl/src/m/classes/geometry.py	(revision 19572)
+++ /issm/trunk-jpl/src/m/classes/geometry.py	(revision 19573)
@@ -49,5 +49,5 @@
 		md = checkfield(md,'fieldname','geometry.base'      ,'NaN',1,'size',[md.mesh.numberofvertices])
 		md = checkfield(md,'fieldname','geometry.thickness','NaN',1,'size',[md.mesh.numberofvertices],'>',0,'timeseries',1)
-		if any((self.thickness-self.surface+self.base)>10**-9):
+		if any(abs(self.thickness-self.surface+self.base)>10**-9):
 			md.checkmessage("equality thickness=surface-base violated")
 		if solution==TransientSolutionEnum() and md.transient.isgroundingline: