This page describes only the use and application of Coordinate Reference Systems in Orbit.
For a clear and short overview of the concepts of coordinate systems, datum and projections, read crs_theory.

• Supported CRS
  • EPSG Library
  • Local CRS Definitions
  • Custom CRS Definition
  • Vertical CRS Definitions - Geoid or DEM
• Dataset CRS
• MapCanvas CRS

A coordinate reference system (CRS) or spatial reference system (SRS) is a coordinate-based local, regional or global system used to locate geographical entities referring to a horizontal or vertical reference frame.. A coordinate reference system defines inter alia the representative volume of the earth, in case of projected systems the map projection method and the transformation between different spatial reference systems.
Coordinate reference systems can be referred to using a SRID integer, including EPSG codes defined by the International Association of Oil and Gas Producers.

Read more, crs_theory.

Orbit has the objective to support coordinate systems as they are defined by the OGP (International Association of Oil and Gas Producers) and described in the EPSG library.

Up to now Orbit supports any combination Geographic, Geocentric and Metric projected coordinate systems ¹⁾.
If it is your wish to use Feet projected coordinate system, please let us know. It is on our wishlist for a future update.

The following local coordinate are supported as defined by their local entity, both for XY and Z.

Contact the Orbit support to embed your local defined coordinate system.

The EPSG dataset does not and cannot record all possible geodetic parameters in use around the world. Orbit supports custom created CRS definitions if they are structured as well-known text as described by the Open Geospatial Consortium :

• International documentation : Well-known-text (WKT).
• Practical documentation for use in Orbit : prj

1. Create a plain ASCII text file with the extension .prj and insert the projection parameters as a WKT (well known text) definition on a single line
2. The prj-file should be placed in the “<installdir>\program\system\crs” directory
3. The name of the file should be a numeric code, like “1031370.prj” for example.
   The numeric code should be larger than 1000000 (one million) to avoid overlap with existing EPSG codes. An optional description can be added to the filename if an underscore character follows the numeric code, like “1031370_Belge 1972 - Belgian Lambert 72.prj” for example.
4. After starting Orbit the newly added CRS systems can be found by selecting “Undefined Area” from the CRS area (By Country) list.

Since Orbit 10.5 an intelligent engine can be used to add any geoid model or dem via an Orbit raster file or via a mathematical description.

To support your local geoid model in Orbit you can provide your geoid (raster) definition and specifications to the Orbit support team (support[at]orbitgis.com).

This can be as text/csv file (containing X,Y,Z) or any supported raster resource.
The Orbit team will process the required configuration files which can be added on the fly like a custom CRS definition.

Every single resource has a CRS.
If no Orbit datsaet CRS is set, Orbit will read the resource assuming that dataset has the same coordinate system as the MapCanvas (see below). When combining resources with different coordinate system it is strongly recommended to define the coordinate system for every single resource.

There are two ways to set the CRS of a dataset in Orbit :

• general
• context_menu

The dataset CRS is saved in the Orbit Resource Descriptor file :

• ord

The MapCanvas CRS is the coordinate system that will be used as display coordinate system for all your listed datasets. If required datasets will be re-projected on the fly to be displayed on the MapCanvas.
But make a wise decision :

• It will require processing power to reproject large vector datasets into another MapCanavas CRS. It is advised to use the CRS of the largest vector dataset or combination of datasets as MapCanvas CRS. This will reduce re-projection calculations and will speed up map rendering considerably.
• Re-projecting means deforming. To retain your familiar “projection shapes” use again the same CRS for your MapCanavas as defined for your datastets.

The MapCanavas CRS can be changed quickly via the Set Coordinate Reference System Window which one opens with a single click on the current MapCanvas CRS in the middle of the MapCanvas Statusbar.

The MapCanvas CRS will follow automatically the CRS of the first checked / displayed dataset with a defined CRS.

The MapCanvas CRS will be saved in the workspace :

• Orbit Standalone : ogw
• Orbit Client Server : workspace