The AllTrans EGM2008 Calculator is a free geodetic utility developed by Hans-Gerd Duenck-Kerst. It computes global EGM2008 geoid undulations to convert Global Navigation Satellite System (GNSS/GPS) ellipsoidal heights into precise orthometric heights (height above Mean Sea Level). Key Features & Technical Details
Core Function: It calculates the precise separation (undulation) between the WGS84 reference ellipsoid and the EGM2008 gravity geoid model.
Input Flexibility: Supports manual point inputs, batch file processing (like ASCII datasets), and geoid grid computations.
NMEA Integration: Capable of directly modifying Mean Sea Level (MSL) heights and geoid undulations within live or recorded NMEA GGA data streams.
Software Specs: It is a lightweight Windows-compatible software (~7.3 MB file size) that serves as a dedicated component of the larger, premium AllTrans Coordinate Transformation Suite. Utility in Precise Surveying
GNSS equipment natively captures height relative to a mathematically smooth ellipsoid (
), which does not account for local gravity. Land surveyors, civil engineers, and hydrologists require orthometric height ( ) relative to actual sea level. By using the formula
is the geoid undulation calculated by the software), surveyors can instantly achieve centimeter-level vertical precision without needing extensive, manual leveling equipment lines over long distances. Software Availability & Downloads
The standalone calculator is freeware and can be downloaded from platforms like the AllTrans EGM2008 Calculator Soft112 Portal.
Note: While version 1.2 remains widely utilized in field surveying workflows, it is an older tool. For broader, modern deployments across multi-model gravimetric projects, many agencies utilize updated online web applications such as the UNAVCO Geoid Height Calculator or the official ICGEM Calculation Service. If you are setting up a workflow, tell me:
What GNSS receiver model or raw data format (e.g., RINEX, NMEA) you are using?
What local vertical datum or target reference frame your project requires?
I can provide the exact steps to convert your field coordinates accurately.
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