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What is an RTCM CRS?
An RTCM coordinate reference system (CRS) is a coordinate system created from the RTCM messages included in the GNSS differential corrections sent by certain mount points of some NTRIP servers.
RTCM messages have a number that identifies them and, in this case, those that include information on coordinate transformations range from identifier 1021 to 1027.
The following table describes what each one includes:
RTCM Message | Description / Function |
|---|---|
1021 | Helmert/Abridged Molodensky Transformation (Control) – Defines the transformation parameters between datums. |
1022 | Molodensky‑Badekas Transformation (Control) – Alternative transformation method. |
1023 | Ellipsoidal Datum Change Grid Residual – Corrects local or regional distortions. |
1024 | Plane Grid Residual – For adjustments in cartographic projections. |
1025 | Projection – Defines cartographic projection parameters (e.g., UTM). |
1026 | Lambert Conformal Conic Projection – Defines Lambert projection. |
1027 | Oblique Mercator Projection – Defines oblique Mercator projection. |