Index: trunk/doc/release.2015/ps1.datasystem/datasystem.tex
===================================================================
--- trunk/doc/release.2015/ps1.datasystem/datasystem.tex	(revision 40565)
+++ trunk/doc/release.2015/ps1.datasystem/datasystem.tex	(revision 40566)
@@ -776,7 +776,4 @@
 \label{sec:warp}
 
-\note{re-read and improve the text: better description of RINGS.V3 and
-  other related tessellations.}
-
 The \ippstage{warp} stage transforms the image pixels from the regular
 grid laid out on the chips in the camera to a system of pixels with
@@ -792,7 +789,7 @@
 centers are typically separated by several degrees on the sky; for
 pixel scales appropriate to GPC1, the resulting collection of pixels
-would be unwieldy in terms of memory in the processing computer.  The
+would be unwieldy in terms of memory in the processing computers.  The
 pixel grid is thus subdivided into smaller sub-images called
-'skycells'.
+`skycells'.
 
 A tessellation can be defined for a limited region, with only a small
@@ -800,10 +797,10 @@
 even a single projection center (e.g., for the Medium Deep fields).
 For the $3\pi$ survey, the tessellation contains projection centers
-covering the entire sky.  The version used to for the PV3 analysis is
+covering the entire sky.  The version used for the PV3 analysis is
 called the \ippmisc{RINGS.V3}.  In this tessellation, projection
 centers are spaced every four degrees in DEC and the RA spacing is
 approximately four degrees as well, adjusted to ensure an integer
 number of equal-sized regions.  \ippmisc{RINGS.V3} uses a pixel scale
-of $0\farcs{}25$ per pixel.  The projections subdivided into a
+of $0\farcs{}25$ per pixel.  The projections are subdivided into a
 $10\times{}10$ grid of skycells, with an overlap region of
 60\arcsec\ between adjacent skycells to ensure that objects of modest
@@ -812,11 +809,12 @@
 $y$ direction and east to the negative $x$ direction.  The
 tessellations used by the IPP are stored in the DVO format (see
-Section~\ref{sec:DVO}), with \ippdbtable{SkyTable} entries defining
-the projection centers and image boundaries for all skycells.
+Section~\ref{sec:DVO}).  A table in the processing database,
+\ippdbtable{SkyTable}, lists the projection centers and image
+boundaries for all skycells.
 
 The first step of the \ippstage{warp} stage is to determine which
 skycells overlap with the input exposure.  These overlaps are
 determined by the \ippprog{dvoImageOverlaps} program, which compares
-the astrometrically calibrated catalog from the \ippstage{camera}
+the astrometrically-calibrated catalog from the \ippstage{camera}
 stage to the DVO database defining the target tessellation.  The
 output of this command is used to populate the
@@ -829,11 +827,12 @@
 \ippstage{chip} stage images (including the variance images and the
 updated masks) to the \ippprog{pswarp} program.  For details on the
-warping algorithm, see \cite{waters2017}.  The output of this program
-are the geometrically transformed images containing all input pixels
-warped to the common skycell pixel grid, which can subsequently be
-used for stacking and difference image analysis.  For the $3\pi$
-survey data, the signal, mask, and variance images generated at this
-stage are being made available from the image extraction tools at the
-MAST archive at STScI as part of the DR2 data release.  
+warping algorithm, see \cite{waters2017}.  The outputs of this program
+are the geometrically transformed images (signal, variance, and mask)
+containing all input pixels warped to the common skycell pixel grid,
+These can subsequently be used for stacking and difference image
+analyses.  For the $3\pi$ survey data, the signal, mask, and variance
+images generated at this stage are being made available from the image
+extraction tools at the MAST archive at STScI as part of the DR2 data
+release.
 
 %% A catalog is