Differences

This shows you the differences between two versions of the page.

--- projection_type [2013/03/01 03:04]
admin
+++ projection_type [2016/11/22 21:59]
hermann [Using a Proj4 description]
@@ Line 1: / Line 1: @@
 ====== Projection Type ======
-Represents a [[wp>Map_projection|map projection]].
+Represents a [[wp>Map_projection|map projection]]. Projections can be defined using the predefined options (UTM, Geodetic etc), using a WKT specification, using an EPSG code or using a Proj4 specification.
+WKT specifications must follow the [[wkt format|standard syntax]]. See the example below:
+    PROJCS["SUTM21",
+        GEOGCS["SOUTH AMERICAN 1969",
+            DATUM["SAD69",
+                SPHEROID["INT67",6378160,298.25]],
+            PRIMEM["Greenwich",0],
+            UNIT["degree",0.0174532925199433]],
+        PROJECTION["Transverse_Mercator"],
+        PARAMETER["latitude_of_origin",0],
+        PARAMETER["central_meridian",-57],
+        PARAMETER["scale_factor",0.9996],
+        PARAMETER["false_easting",500000],
+        PARAMETER["false_northing",10000000],
+        UNIT["Meter",1]]
+The Proj4 syntax must also follow the [[http://proj4.org/parameters.html|Proj4 specification syntax]]. Example:
+    [ +proj=latlong +ellps=GRS80 +towgs84=-199.87,74.79,246.62 ]
 ===== GUI Editor =====
-[{{ :editors:projection_editor.png?nolink& |Graphical representation of the projection editor}}]
+[{{ :editors:projection_editor.png?nolink&500 |Graphical representation of the projection editor}}]
 ===== EGO Script =====
@@ Line 23: / Line 43: @@
 [| "LATLONG", "GEODETIC", "WGS84", "METERS" |]
 </code>
 ==== Using a WKT (Well-Known Text) description ====
@@ Line 55: / Line 76: @@
        PARAMETER["false_northing",-2000000],
        UNIT["METERS",1]]]
+|]
+</code>
+==== Using a Proj4 description ====
+<code cpp>
+[| "COORDINATE_TYPE", [ PROJ4_PROJECTION ] |]
+</code>
+The syntax used to the represent the PROJ4_PROJECTION can be found [[http://proj4.org/parameters.html|here]].
+Example:
+<code cpp>
+[| "LATLONG",
+   [ +proj=longlat +ellps=WGS84 +towgs84=0,0,0,0,0,0,0 +no_defs ]
+|]
+</code>
+==== Using a EPSG code ====
+<code cpp>
+[| "COORDINATE_TYPE", EPSG_CODE ] |]
+</code>
+Example:
+<code cpp>
+[| "LATLONG",
 |]
 </code>
@@ Line 60: / Line 109: @@
 ----
 A COORDINATE_TYPE is also case-insensitive and must be represented using keywords "en" (Easting/Northing), "latlong" (Latitude/Longitude) and "none". The latter  can be used to automatically derive the coordinate type based on the projection parameters.
+===== Automatic Conversions =====
+  * **Converted from**: [[Map Type]] and [[Categorical Map Type]].
+  * **Converted to**: None.