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What is a geographic transformation?
A geographic datum transformation is a calculation used to convert between two geographic coordinate systems to ensure that data is properly aligned. Geographic coordinate systems describe how locations on the earth are placed on a hypothetical reference spheroid.
Is a geographic coordinate system a projection?
A geographic coordinate system (GCS) is a reference framework that defines the locations of features on a model of the earth. A projected coordinate system (PCS) is flat. It contains a GCS, but it converts that GCS into a flat surface, using math (the projection algorithm) and other parameters.
How are geographic transformations used in the projection process?
This geographic or datum transformation is often embedded in the procedure to convert between coordinate systems, or in other words, the projection process. This process often involves more than one coordinate transformation. For example, let’s say you want to convert between two projected coordinate systems.
When do you have to choose the geographic transformation?
SO – when you are asked to select the geographic transformation, you are being asked to choose which mathematical calculation will be used to convert coordinates referenced to one datum to coordinates referenced to another datum.
Are there any transformations available in ArcGIS project?
There are no transformations available between the input and output geographic coordinate systems (GCS). The input dataset or feature class has an unsupported or a custom GCS. To resolve the first issue, define the projection of the data using an available coordinate system in ArcGIS Desktop before transforming the GCS using the Project tool.
Clicking the warning icon in the Geographic Transformation section in the Project tool window returns the following warning message: ” WARNING 001839 A datum transformation is expected, but the parameter is empty.” The Geographic Transformation drop-down list is generated by the Projection Engine.