====== Projection Type ======

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|WKT 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&500 |Graphical representation of the projection editor}}]

===== EGO Script =====

A constant representing a projection in a [[EGO Script]] can be defined in two different ways:

==== Using ERMapper parameters ====

<code cpp>
[| "COORDINATE_TYPE", "ERMAPPER_PROJECTION", "ERMAPPER_DATUM", "ERMAPPER_UNIT" |]
</code>

All parameters are case-insensitive and must be surrounded by double quotes.

Example:
<code cpp>
[| "LATLONG", "GEODETIC", "WGS84", "METERS" |]
</code>

==== Using a WKT (Well-Known Text) description ====

<code cpp>
[| "COORDINATE_TYPE", WKT_PROJECTION |]
</code>

The syntax used to the represent the WKT_PROJECTION can be found [[wkt format|here]].

It is worth nothing that only the COORDINATE_TYPE must be surrounded by double quotes.

Example:
<code cpp>
[| "LATLONG",
   PROJCS["unnamed",
       GEOGCS["WGS 84",
           DATUM["WGS_1984",
               SPHEROID["WGS 84",6378137,298.257223563,
                   AUTHORITY["EPSG","7030"]],
               TOWGS84[0,0,0,0,0,0,0],
               AUTHORITY["EPSG","6326"]],
           PRIMEM["Greenwich",0,
               AUTHORITY["EPSG","8901"]],
           UNIT["degree",0.0174532925199433,
               AUTHORITY["EPSG","9108"]],
           AUTHORITY["EPSG","4326"]],
       PROJECTION["Transverse_Mercator"],
       PARAMETER["latitude_of_origin",0],
       PARAMETER["central_meridian",90],
       PARAMETER["scale_factor",0.9996],
       PARAMETER["false_easting",500000],
       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",
   7030
|]
</code>

----
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.