From fff37a106352de2e859829710ba2f8e272cd41d8 Mon Sep 17 00:00:00 2001
From: Frank Warmerdam <warmerdam@pobox.com>
Date: Tue, 30 Apr 2002 17:05:17 +0000
Subject: Added epsg item

git-svn-id: http://svn.osgeo.org/metacrs/proj/trunk@1014 4e78687f-474d-0410-85f9-8d5e500ac6b2
---
 html/faq.html | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

(limited to 'html')

diff --git a/html/faq.html b/html/faq.html
index da4ff0e4..655080da 100644
--- a/html/faq.html
+++ b/html/faq.html
@@ -104,6 +104,37 @@ include expanding the definition of +datum clause. <p>
 
 </ol>
 
+<!-------------------------------------------------------------------------->
+
+<h2>How do I use EPSG coordinate system codes with PROJ.4?</h2>
+
+There is somewhat imperfect translation between 2d geographic and
+projected coordinate system codes and PROJ.4 descriptions of the
+coordinate system available in the <tt>epsg</tt> definition file that
+normally lives in the <tt>proj/nad</tt> directory.  If installed (it is
+installed by default on Unix), it is possible to use EPSG numbers like this:
+
+<code>
+% cs2cs -v +init=epsg:26711
+# ---- From Coordinate System ----
+#Universal Transverse Mercator (UTM)
+#       Cyl, Sph
+#       zone= south
+# +init=epsg:26711 +proj=utm +zone=11 +ellps=clrk66 +datum=NAD27 +units=m
+# +no_defs +nadgrids=conus,ntv1_can.dat
+#--- following specified but NOT used
+# +ellps=clrk66
+# ---- To Coordinate System ----
+#Lat/long (Geodetic)
+#
+# +proj=latlong +datum=NAD27 +ellps=clrk66 +nadgrids=conus,ntv1_can.dat
+</code>
+
+The <tt>proj/nad/epsg</tt> file can be browsed and searched in a text editor 
+for coordinate systems.  There are known to be problems with some coordinate
+systems, and any coordinate systems with odd axes, a non-greenwich prime
+meridian or other quirkyness are unlikely to work properly.  Caveat Emptor!<p>
+
 
 <!-------------------------------------------------------------------------->
 
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