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1. What is KSA-GEOID17?
KSA-GEOID17 is a geoid model for the Kingdom of Saudi Arabia determined by using land, ship-borne and GOCE satellite gravity data, and satellite altimetry and GPS levelling data. The KSA-GEOID17 is a major component of KSA-VRF, which allows to compute orthometric heights for the points over KSA different from KSA-NVN benchmarks.
2. How accurate is KSA-GEOID17?
Accuracy of KSA-GEOID17 is not homogeneous through the while kingdom due to the distribution of the input data, the accuracy of derived orthometric height from KSA-GEOID is:​
  • ≈2-3 cm in the Eastern region with good data coverage and close to GPS/Leveling points.
  • ≈10-20 cm in the rest of KSA.
3. What will be the accuracy of orthometric heights if KSA-GEOID17 is used?
The accuracy of orthometric heights computed by using KSA-GEOID17 model will depend on the two following factors:
  • Accuracy of the KSA-GEOID17 model (see FAQ 2).
  • Accuracy of the ellipsoidal height provided by the user.
4. Who is responsible for maintaining the KSA-GEOID?
General Authority for Survey and Geospatial Information (GASGI, former GCS).
5. How can I access and use KSA-GEOID17?
There are several ways how to do it:
  • You can use KSA-CORS network services and transform your observed ellipsoidal heights in online mode.
  • If you need geoid heights for single points or grid, please, contact us  by e-mail address info@gcs.gov.sa
6. What is the resolution of the KSA-GEOID17 model?
Original resolution of the KSA-GEOID17 model is 2 x 2 km. If you would like to access the model for generating a grid of geoid heights for some local area, please, contact us by e-mail address info@gcs.gov.sa
7. What are the geoid models available in KSA?
The only previous geoid model was KSA-GEOID09.
8. How can I convert data from KSA-GEOID09 to KSA-GEOID17?
A specially designed online tool is ready for use by you. Please, follow this link Online KSA-GEOID Transformation Tool  to transform geoid height of a single point (manual input) or geoid heights of multiple points (file input).
9. How  to transform my data from KSA-GEOID09 to KSA-GEOID17 using Online Height Transformation Tool?
If you have only one point then you will need the following input data:
  • Latitude & Longitude of your point in decimal degrees or degrees, minutes and seconds.
  • Geoid height in KSA-GEOID09.
If you will have more than one point and you can enter the above mentioned values, separated by single space, into the ASCII text file (*.txt or *.dat extension) in the following order:
Latitude
Space delimiter​Longitude​Space delimiter​Orthometric height​
​Latitude​Space delimiter​Longitude​​Space delimiter​​Orthometric height​​
.....​.....​.....​.....​.....​
​Latitude​Space delimiter​Longitude​​Space delimiter​​Orthometric height
​​​​
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