A coordinate system is a reference system used to represent the locations of project data within a common coordinate framework. Coordinate systems are geographic (latitude-longitude), geocentric (X, Y, Z), or projected (X, Y). A coordinate system can optionally include a vertical datum that defines the origin for height values. Each coordinate system is defined by a Well-Known Text (WKT) definition string, a simple structured, text-based format for spatial reference system information that is easy to store and share between systems (See http://portal.opengeospatial.org/files/?artifact_id=999 and https://en.wikipedia.org/wiki/Well-known_text_representation_of_coordinate_reference_systems).
All project layers must be displayed in the terrain coordinate system. When you add a new layer to a project, TerraExplorer tries to read its coordinate system. If TerraExplorer is able to do so, it automatically reprojects the layer to the project’s coordinate system.
If your project layers use coordinate systems with different vertical datums, vertical datum grid shift files in GTX format are used to shift and transform between these datums, by offsetting the vertical input coordinates by a specific amount. Sometimes the Well-Known Text (WKT) of one of the coordinate systems in your project references a particular GTX file that was not bundled with your installation, or the reference itself is missing from the WKT. In this case, you can manually add the missing GTX information. More about: How to add missing GTX information >
If a layer does not include coordinate system information or TerraExplorer is unable to read this information, you can indicate the coordinate system of this source, as provided by the data supplier, in the Coordinate System dialog box. TerraExplorer then converts the layer data to the project’s coordinate system. Although the source file retains its original coordinate system, it is placed on the terrain according to the reprojection parameters.
The Coordinate System dialog box is a high-level dialog box that allows you to select, view, and edit a coordinate system. You can also use this dialog box to define new coordinate systems that are not already defined. This dialog box is accessed in the following cases:
- To manually define the coordinate system of a project’s base MPT (Project Settings, Terrain Database tab). More about: Setting the terrain database coordinate system >
- To define a feature, raster, or point cloud layer's coordinate system so TerraExplorer can reproject it to the project’s coordinate system (Layer’s property sheet, in the Coordinate System field).
- To change a navigation map’s coordinate system (Navigation Map Settings dialog box. More about: Changing a navigation map's coordinate system >
More about: Using the coordinate system dialog box >