Changes between Version 3 and Version 4 of UserGuide

Timestamp:

Jul 10, 2008, 12:52:21 PM (16 years ago)

Author:

madair

Comment:

--

UserGuide

@@ -1 @@
-=== User Guide ===
+= User Guide =
 
-Using Proj4js is a matter of including the library in your page, creating source and destination Proj objects, transforming point coordinates.  
+Using Proj4js is a matter of:
+ 1. including the library in your page
+ 1. creating source and destination Proj4js objects
+ 1. transforming point coordinates.  
 
 {{{
+// include the library
+<script src="lib/proj4js-combined.js"></script>  //adjust the path for your server
+                                                 //or else use the compressed version
 
-<script src="lib/proj4js-combined.js"></script>  //adjust the path for your server
+. . .
 
-…
-//somewhere in your JavaScript code where you need this
-
+// creating source and destination Proj4js objects
+// once initialized, these may be re-used as often as needed
 var source = new Proj4js.Proj(‘EPSG:4236’);    //source coordinates will be in Longitude/Latitude
 var dest = new Proj4js.Proj(‘EPSG:27563’);     //destination coordinates in LCC, south of France
 
+. . .
+
+// transforming point coordinates
 var p = new Proj4js.Point(-76.0,45.0);   //any object will do as long as it has 'x' and 'y' properties
 Proj4js.transform(source, dest, p);      //do the transformation.  x and y are modified in place
 
 //p.x and p.y are now EPSG:27563 easting and northing in meters
-…
+. . .
+}}}
 
-}}}
+'''Note:''' Proj4js currently depends on some core [http://openlayers.org/ OpenLayers] classes which are compiled into the file OLprotoype.js.  If you are using Proj4js in a page that already includes the OpenLayers library, there is no need to include this file, otherwise you must also include OLprototype in a <script> tag.  The development plan for Proj4js is to factor out this requirement so that the OpenLayers classes will only be required for dynamic lookup of the CRS definitions (see below).
 
 == Proj4js.Proj constructor ==
 
-Every Proj object must be initialized with the parameters of the CRS to be used.  The argument to the constructor is a key in the Proj4js.defs initialization parameters object.
+Every Proj4js.Proj object must be initialized with the parameters of the CRS to be used.  The argument to the constructor is a key in the Proj4js.defs object.
 
 
@@ -31 +40 @@
 }}}
 
-Proj4js uses the same initialization parameters that PROJ4 uses [link] and these values must be defined before the constructor is called.
+Proj4js uses the same initialization parameters that [wiki:proj] uses and these values must be defined before the constructor is called.
 
 == If you know the projections to be used in your application ==
@@ -43 +52 @@
 == Dynamic lookup of initialization parameters ==
 
-set libPath
-set proxy
-spatialreference.org
+If you don't know the CRS's to be used by the application, Proj4js can dynamically look up the initialization parameters at run-time.  By default, it will use the REST web service at [http://spatialreference.org spatialreference.org] as the lookup service.
+
+To use Proj4js in this way, you will need to:
+ 1. include the OLprotoype.js file in a script tag (only if your page doesn't already include OpenLayers)
+ 1. define a proxy script to allow cross domain HTTP requests
+ 1. define the value for the /lib path
+
+The way dynamic definition string lookup works is to first check for the definition at the path lib/defs.  If the appropriate file is found there, it will be loaded and used by Proj4js.  If it is not found there ('''note:''' in this case it is normal to see an error in the Firebug console), an HTTP request will be issued to spatialreference.org