DatumShiftInfo.OriginalAccuracy Property
Gets the original accuracy of the datum shift (in the area of use).
Syntax
public System.Double OriginalAccuracy { get; }Property Value
Default: 999
The original accuracy of the datum shift in meters.
Remarks
The original accuracy is usually the same as the ordinary Accuracy, but sometimes there is an interesting difference.
Carmenta Engine requires datum shifts that transform to Wgs84, but many of these were originally published as transforming to a ground-fixed version of Wgs84, like ETRS89 in Europe, GDA94 in Australia or SIRGAS 2000 in South America. When transforming to a ground-fixed version of Wgs84, the original datum shifts may have submeter accuracy. For example, there is a datum shift from CH1903+ to ETRS89 with 0.1 meter accuracy.
EPSG will publish such datum shifts in two versions: the original version and a cloned version that transforms to Wgs84. For the cloned version to Wgs84, EPSG will set the accuracy to be at least 1 meter, to account for tectonic motion since the ground-fixed datum was defined. (Tectonic motion makes the ground-fixed datums diverge from Wgs84 by up to 10 cm per year, so the current differences are typically in the range 0.5 to 1.5 meters.)
So, for the datum shift from CH1903+ to Wgs84, Carmenta will consider the Accuracy to be 1 meter in accordance with EPSG, but we consider the OriginalAccuracy to be 0.1 meter.
For the meaning of the special values 999 meters (the default) and 1111 meters, see Accuracy.
Platforms
Windows, Linux, Android