# Coordinate Systems & Datums RTKdata corrections are available in multiple geodetic reference frames. The mountpoint you choose determines the coordinate system of the corrections streamed to your device. *** ## Mountpoints RTKdata provides four mountpoints. Names are **case-sensitive** and must be entered in **ALL CAPS**. | # | Mountpoint | Details | | - | ------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------- | | 1 | **`AUTO`** | Regional Geodetic Coordinate System (RGCS) — automatically delivers corrections in your region's local datum. **Recommended for most workflows.** | | 2 | **`AUTO_ITRF2020`** | ITRF2020 Geodetic Coordinate System at epoch 2015.0 | | 3 | **`AUTO_ITRF2014`** | ITRF2014 Geodetic Coordinate System with current epoch | | 4 | **`AUTO_WGS84`** | WGS84(G2139) in the middle of the current year (e.g., 2025.5 for year 2025, 2024.5 for year 2024) | > **Recommendation:** Use `AUTO` unless your project specifically requires a global reference frame. AUTO eliminates the most common source of coordinate shifts by delivering corrections in your regional datum. *** ## Regional Geodetic Coordinate System (RGCS) When you connect with the `AUTO` mountpoint, RTKdata automatically selects the correct regional geodetic coordinate system based on your location. The table below shows exactly which datum and epoch is delivered per region. | # | Geodetic Coordinate System Name | Epoch # | Effective Regions | | -- | ------------------------------------------ | ------------- | -------------------- | | 1 | **NAD83(2011)** | 2010.0 | USA | | 2 | **NAD83(PA11)** | 2010.0 | USA Hawaii | | 3 | **NAD83(MA11)** | 2010.0 | Guam | | 4 | **NAD83(CSRS)v7** | 2010.0 | Canada | | 5 | **ETRS89(ETRF2010)(2010.0)** | 2010.0 | Europe | | 6 | **GDA2020(2020.0)** | 2020.0 | Australia | | 7 | **NZGD2000(2000.0)** | 2000.0 | New Zealand | | 8 | **TUREF(2005.0)=ITRF96(2005.0)** | 2005.0 | Turkey | | 9 | **ITRF2008(2005.0)=ITRF2008(2005.0)** | 2005.0 | India | | 10 | **ITRF2008(2011.811)** | 2011.811 | Egypt | | 11 | **NGD2012(2012.0)=ITRF2008(2012.0)** | 2012.0 | Nigeria | | 12 | **PGD2020=ITRF2014(2020.044)** | 2020.044 | Philippines | | 13 | **ITRF2014(2010)** | 2010.0 | Mexico | | 14 | **ITRF2014** | current epoch | Kenya | | 15 | **CGCS2000(2000.0)=ITRF97(2000.0)2** | 2000.0 | China | | 16 | **JGD2011(2011.3945)=ITRF2008(2011.3945)** | 2011.3945 | Japan | | 17 | **IGRS2013(2012.0)=ITRF2008(2012.0)** | 2012.0 | Indonesia | | 18 | **ITRF1991(1994.0)** | 1994.0 | South Africa | | 19 | **WGS84(G730)(1994.0)** | 1994.0 | Sri Lanka | | 20 | **ITRF2020(2025.0)** | 2025.0 | Taiwan | | 21 | **ITRF2014(2010)** | 2010.0 | Thailand | | 22 | **KGD2002(2002.0)=ITRF2000(2002.0)** | 2002.0 | South Korea | | 23 | **MGRF2020(2020.0)=ITRF2020(2020.0)** | 2020.0 | Malaysia | | 24 | **MTRF2000(2004.0)=ITRF2000(2004.0)** | 2004.0 | United Arab Emirates | | 25 | **SIRGAS2000(2000.4)=ITRF2000(2000.4)** | 2000.4 | South America | | 26 | **GGD=ITRF2008(2011.353)** | 2011.353 | Georgia | | 27 | **WGS84(G2139)(20xx.5)1** | 20xx.5 | Other regions | > **Note:** For regions not listed above, `AUTO` falls back to WGS84(G2139) at the mid-year epoch. *** ## Why Your Coordinates May Be Offset If you see a consistent **50 cm – 1 m offset** compared to local survey control, this is almost certainly a **datum mismatch**, not an accuracy problem. The earth's tectonic plates move. Global frames like ITRF2014 track current plate positions, while regional datums (NAD83, ETRS89, GDA2020) were fixed at a specific point in time. The difference grows every year. **This is not a bug — it's physics.** **The Fix:** 1. **Use `AUTO`** — it delivers corrections in your regional datum, eliminating the shift in most cases. 2. **Software transformation:** If you must use a global mountpoint (`AUTO_ITRF2020`, `AUTO_WGS84`), set your rover/drone software to transform from WGS84/ITRF to your local system. *** ## Vertical Reference: Ellipsoidal vs. Orthometric Heights RTKdata provides **ellipsoidal heights** (height above the WGS84 ellipsoid). These are NOT the same as: * Mean Sea Level (MSL) * Orthometric height * Local vertical datum To convert to orthometric heights, apply a **geoid model** in your software: * **EGM96 / EGM2008** — global geoid models * **OSGM15** — UK geoid model * **GEOID18** — US geoid model * **AUSGeoid2020** — Australian geoid model Most surveying software and GIS applications can apply geoid corrections automatically when the correct vertical datum is selected. See [Understanding Heights](https://docs.rtkdata.com/get-started/understanding-heights) for a detailed guide. *** ## US Survey Feet vs. International Feet If you see a steady **\~4 ft / 1.2 m offset** in the United States, check your controller's unit settings. The difference between US Survey Feet and International Feet causes a noticeable shift at scale. **Fix:** Set your controller/software project to use the correct foot definition for your state. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.rtkdata.com/get-started/coordinate-systems-and-datums.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.