Follow me to model your own geoid quickly using SRBF, then you will be pleasantly surprised!

Demonstrates a streamlined, six-step workflow for all-element gravity field modeling based on the Spherical Radial Basis Function (SRBF) approximation method on both the ground and the geoid. The approach directly utilizes observed gravity disturbances (terrestrial, marine, and airborne) and GNSS-leveling height anomalies (or geoidal heights) without employing complex schemes of terrain effects and traditional pre-processing. This workflow aims to facilitate a rapid understanding of key aspects in spectral-domain local SRBF modeling, including observation data analysis, computational quality control, and gravity field reconstruction techniques.

🌏 Primary Data Sources

(1) Observed Gravity Disturbances (obsdistgrav.txt)

Format: Point ID/Station Name, Longitude (decimal degrees), Latitude (decimal degrees), Ellipsoidal Height (m), Observation Gravity Disturbance (mGal).

(2) GNSS-Leveling Observation Height Anomalies (obsGNSSlksi.txt)

Format: Point ID/Station Name, Longitude (decimal degrees), Latitude (decimal degrees), Ellipsoidal Height (m), Observation Height Anomaly or Geoidal Height (m).

Normal Height System: The "Ellipsoidal Height" attribute corresponds to the GNSS-derived ellipsoidal height at the GNSS-leveling site.

Orthometric Height System: The observation geoidal height represents the ellipsoidal height of the geoid. In the file record, this value populates the "Ellipsoidal Height" field.

Note: The SRBF-based all-element modeling workflow is identical for both height systems; only the appropriate ellipsoidal heights for the GNSS-leveling sites are required. This example employs observation height anomalies under the Normal Height System. Both datasets are simulated by adding noise to EGM2008 model values (degrees 1 – 1800).

(3) Computation Surface Ellipsoidal Height Grids

For Geoidal Modeling: The computation surface is defined by the model geoidal height grid. In this example: mdlgeoidh30s.dat.

For Ground Modeling: The computation surface is defined by the ground ellipsoidal height grid. In this example: surfhgt30s.dat (= Land-Sea DEM DEM30s.dat + Model Geoidal Height mdlgeoidh30s.dat).

Model Derivation: Model geoidal heights and ground height anomalies are derived from a 180-degree gravity field model (steps omitted).

Requirement: The extent of the computation surface grid must exceed the target extent to mitigate edge effects.