PDFlib 8 Windows COM/.NET Tutorial

EPSG. EPSG is a collection of thousands of coordinate systems which are referenced
via numeric codes. EPSG is named after the defunct European Petroleum Survey Group and
now maintained by the International Association of Oil and Gas Producers (OGP).
EPSG reference codes point to one of the coordinate systems in the EPSG database.
The full EPSG database can be downloaded from the following location:
www.epsg.org
Well-known text (WKT). The WKT (Well-Known Text) system is descriptive and consists
of a textual specification of all relevant parameters of a coordinate system. WKT is specified
in the document OpenGIS® Implementation Specification: Coordinate Transformation
Services, which has been published as Document 01-009 by the Open Geospatial Consortium
(OGC).It is available at the following location:
www.opengeospatial.org/standards/ct
WKT has also been standardized in ISO 19125-1. Although both WKT and EPSG can be
used in Acrobat (and are supported in PDFlib), Acrobat does not implement all possible
EPSG codes. In particular, EPSG codes for geographic coordinate systems don’t seem to
be supported in Acrobat. In this case the use of WKT is recommended. The following
Web site delivers the WKT corresponding to a particular EPSG code:
www.spatialreference.org/ref/epsg
3.7.3 Coordinate System Examples
Examples for geographic coordinate systems. The WGS84 (World Geodetic System)
geographic coordinate system is the basis for GPS and many applications (e.g. Open-
StreetMap). It can be expressed as follows in the worldsystem suboption of the georeference
option:
worldsystem={type=geographic wkt={
GEOGCS["WGS 84",
DATUM["WGS_1984", SPHEROID["WGS 84", 6378137, 298.257223563]],
PRIMEM["Greenwich", 0],
UNIT["degree", 0.01745329251994328]]
}}
The ETRS (European Terrestrial Reference System) geographic coordinate system is almost
identical to WGS84. It can be specified as follows:
worldsystem={type=geographic wkt={
GEOGCS["ETRS_1989",
DATUM["ETRS_1989", SPHEROID["GRS_1980", 6378137.0, 298.257222101]],
PRIMEM["Greenwich", 0.0],
UNIT["Degree", 0.0174532925199433]]
}}
Note EPSG codes for the WGS84 and ETRS systems are not shown here because Acrobat doesn’t seem
to support EPSG codes for geographic coordinate systems, but only for projected coordinate
systems (see below).
94 Chapter 3: Creating PDF Documents (Edition for COM, .NET, and REALbasic)