Index: trunk/psastro/src/psastroFindChip.c
===================================================================
--- trunk/psastro/src/psastroFindChip.c	(revision 24572)
+++ trunk/psastro/src/psastroFindChip.c	(revision 24651)
@@ -110,4 +110,59 @@
 }
 
+// identify chips which land on this column (FP coords)
+bool psastroFindChipInXrange (pmFPA *fpa, int nChip, double xFPA, double yFPA) {
+
+    if (!chipXmin || !chipXmax) {
+	psAbort ("chip bounds not set");
+    }
+
+    if (xFPA <  chipXmin->data.F32[nChip]) return false;
+    if (xFPA >= chipXmax->data.F32[nChip]) return false;
+    return true;
+}
+
+// identify chips which land on this row (FP coords)
+bool psastroFindChipInYrange (pmFPA *fpa, int nChip, double xFPA, double yFPA) {
+
+    if (!chipYmin || !chipYmax) {
+	psAbort ("chip bounds not set");
+    }
+
+    if (yFPA <  chipYmin->data.F32[nChip]) return false;
+    if (yFPA >= chipYmax->data.F32[nChip]) return false;
+    return true;
+}
+
+// return the FPA coordinates of the Y edges of the chip
+bool psastroFindChipYedges (double *yFPAs, double *yFPAe, pmFPA *fpa, int nChip) {
+
+    *yFPAs = chipYmin->data.F32[nChip];
+    *yFPAe = chipYmax->data.F32[nChip];
+    return true;
+}
+
+// return the FPA coordinates of the X edges of the chip
+bool psastroFindChipXedges (double *yFPAs, double *yFPAe, pmFPA *fpa, int nChip) {
+
+    *yFPAs = chipXmin->data.F32[nChip];
+    *yFPAe = chipXmax->data.F32[nChip];
+    return true;
+}
+
+// convert FPA to Chip coordinates
+bool psastroFPAtoChip (double *xChip, double *yChip, pmFPA *fpa, int nChip, double xFPA, double yFPA) {
+
+    pmChip *chip = fpa->chips->data[nChip];
+
+    psPlane ptCH, ptFP;
+    ptFP.x = xFPA;
+    ptFP.y = yFPA;
+    psPlaneTransformApply (&ptCH, chip->fromFPA, &ptFP);
+
+    *xChip = ptCH.x;
+    *yChip = ptCH.y;
+    return true;
+}
+
 bool psastroExtractFreeChipBounds () {