RTK Coordinate Systems & Datums Explained
RTKdata mountpoints and the regional datum each delivers. Fix 50 cm to 1 m coordinate offsets, datum mismatches and ellipsoidal vs orthometric heights.
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RTKdata mountpoints and the regional datum each delivers. Fix 50 cm to 1 m coordinate offsets, datum mismatches and ellipsoidal vs orthometric heights.
RTKdata corrections are available in multiple geodetic reference frames. The mountpoint you choose determines the coordinate system of the corrections streamed to your device.
RTKdata provides four mountpoints. Names are case-sensitive and must be entered in ALL CAPS.
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
AUTOunless your project specifically requires a global reference frame. AUTO eliminates the most common source of coordinate shifts by delivering corrections in your regional datum.
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.
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,
AUTOfalls back to WGS84(G2139) at the mid-year epoch.
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:
Use AUTO — it delivers corrections in your regional datum, eliminating the shift in most cases.
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.
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 for a detailed guide.
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.
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