I have used a mobile application for collecting spatial data. During the data collection, noticed the app records the ellipsoid height. Upon further exploration, I discovered the option to upload a Geoid file. Consequently, I acquired the egm08.gtx file from this link and integrated it into the app’s directory. I would appreciate your insights regarding the accuracy and reliability of the model obtained from the provided link
Usually geoid files are created by government agencies that are established for the mapping and geodetic services for each country.
The geoids themselves are based on precise differential leveling throughout the country to establish geoid-orthographic separation using GNSS methodology.
If the selected geoid was established by a government mapping-geodetic entity (as most are), you can be assured they are very accurate to the standards as stated in their metadata.
Here in the USA, we are very fortunate to have the NGS (National Geodetic Survey) and local state government agencies that help define the geoid model (Geoid18) for the North American continental model. There are also different models for Puerto Rico as well as Alaska and the Pacific plate of Hawaii. Most published accuracies for differential leveling passive marks are within the 2-3 cm separation accuracy for orthometric heights.
A good informational source for the Geoid18 and future models can be read here.
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That is insightful. Thank you
Hi @Edudzi,
The best way to do this is to download the geoid model directly from the source. EGM96 and EGM2008 are published by the National Geospatial-Intelligence Agency (NGA).
OSGeo is open-source and used by millions of users worldwide. Like many other free and open-source software, the community, with thousands of expert developers and scientists, works on making and constantly improving the software, including the reliability of the data shared.