Index: /trunk/pswarp/src/pswarpTransformReadout_Opt.c
===================================================================
--- /trunk/pswarp/src/pswarpTransformReadout_Opt.c	(revision 14799)
+++ /trunk/pswarp/src/pswarpTransformReadout_Opt.c	(revision 14800)
@@ -218,5 +218,5 @@
             float dxOut, dyOut;         // Errors in output coordinates
             dxOut = sqrt(PS_SQR(map->Xx * dxIn) + PS_SQR(map->Xy * dyIn));
-            dxOut = sqrt(PS_SQR(map->Xx * dxIn) + PS_SQR(map->Xy * dyIn));
+            dyOut = sqrt(PS_SQR(map->Yx * dxIn) + PS_SQR(map->Yy * dyIn));
 
             new->modelPSF->params->data.F32[PM_PAR_XPOS] = xOut;