Index: trunk/doc/design/phase4.txt
===================================================================
--- trunk/doc/design/phase4.txt	(revision 10833)
+++ trunk/doc/design/phase4.txt	(revision 10833)
@@ -0,0 +1,39 @@
+
+output from ppImage is (in general) a multiple file, multiple
+extension set of FITS images:
+
+exp01.chipNN.p2.fits
+
+along with the output object files with the associated astrometry:
+
+exp01.chipNN.p2.cmp
+
+for phase3, output is a single MEF file per exposure with one chips
+per extension.  
+
+ISP:
+exp01.p2.fits (image data in PHU)
+exp01.p2.cmp (astrometry data in PHU, object in table, chip mode)
+
+Megacam:
+exp01.p2.fits (one chip per extension)
+exp01.p2.cmp (mosaic astrometry in PHU, chip astrometry per extension)
+
+GPC:
+exp01.chipNN.p2.fits (one chip per extension)
+exp01.chipNN.p2.cmp (astrometry in PHU, chip astrometry per extension)
+
+exp01.p3.cmp (mosaic astrometry in PHU, chip astrometry per extension)
+
+
+user interface to warp:
+
+warp skycell.fits -image exp01.p2.fits -header exp01.p3.cmp output.fits
+ - if -header is not supplied, assume image file contains astrometry
+ - skycell astrometry + NAXIS1,2 defines output grid
+ - output.fits is created (will be replaced if it exists)
+ - allow a subset of the input image to be warped? (specific
+ extensions)
+ - EXTNAME in input.fits is matched to EXTNAME in header.fits
+   - use the WRP / DIS astrometry if available
+