Coordinate systems
The positions of objects on the earth's spherical surface are measured in degrees of latitude and longitude, also known as geographic coordinates. Latitude and longitude are not uniform units of measure; only along the equator does the distance represented by one degree of longitude approximate the same distance of latitude.
To overcome measurement discrepancies, data is often transformed from the three-dimensional geographic coordinate system (GCS) to a two-dimensional planar surface in a projected coordinate system (PCS). Setting the GCS or PCS for a layer is also known as setting its spatial reference. You set the spatial reference for a layer by providing a well-known ID (WKID) or a definition string (well-known text, or WKT).
For Android, iOS, and OS X
When you need to convert a layer from one coordinate system to another, make sure it's on the list of supported mobile datum transformations.
For a complete list of IDs and their corresponding definition strings supported by ArcGIS Runtime for Android and iOS, see the following topics:
For Java, Qt, and WPF
ArcGIS Runtime for Java, Qt, and WPF support the same coordinate systems and transformations that ArcGIS for Desktop supports. For a complete list of supported IDs and their corresponding definition strings, see the following REST API topics:
If your application is having projection difficulty, checking the Additional Projection Engine Transformations check box in the Deployment Builder may address the issue. Checking this check box includes in your deployment data for the transformation methods that require files on disk, such as:
- NADCON
- HARN
- NTv2
For example, checking the check box includes the NAD_1927_To_NAD_1983_NADCON transformation and the AGD_1984_To_GDA_1994_5_NTv2 transformation.
Note that Canadian NTv2 files are not included due to permissions restrictions. For details, see the Esri technical article Where can I get datum transformation grids for Canada?