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Regional Models

Colorado - USA (ColLSMSA-KTH2019)

  Author: J. Ågren   Created: 2019    Resp: J. Ågren  
                       Status: PUBLIC   Licence: CC BY 4.0
The ColLSMSA-KTH2019 gravimetric quasi-geoid and geoid models have been computed by the University of Gävle, the Lantmäteriet and the Royal Institute of Technology (KTH) in Sweden. They have been worked out in the frame of the International Association of Geodesy Joint Working Group 2.2.2 "The 1 cm geoid experiment" and the so called "Colorado experiment". The area covered by the models is 251°E ≤ longitude ≤ 257°E, 36°N ≤ latitude ≤ 39°N with a grid spacing of 1' in both latitude and in longitude. The quasi-geoid is computed using a two-step procedure. First, the terrestrial and de-biased airborne gravity anomalies are gridded using a Remove-Compute-Restore technique and three-dimensional Least Squares Collocation (LSC) with spherical Tscherning and Rapp (1974) type of covariance functions. This step achieves downward continuation of the airborne gravity data and combination with the terrestrial observations. In the second step, the resulting surface gravity anomaly grid is used to compute height anomalies by using Least Squares Modification of Stokes’ formula with Additive corrections (LSMSA or KTH method). The GEOID17RefB global gravity model up to degree 2190 is used in the first gridding step, while the satellite-only GOCO05S model up to degree 240 is used in the second step. Finally, the classical formula by Heiskanen and Moritz (1967) is used for quasi-geoid to geoid conversion. The accuracy of the quasi-geoid and geoid models, when compared against GSVS17 GPS/leveling, is equal to 2.8 cm and 2.7 cm, respectively.

L.E. Sjöberg (2003). A computational scheme to model the geoid by the modified Stokes' formula without gravity reductions. Journal of Geodesy, 77, pp. 423-432. DOI: 10.1007/s00190-003-0338-1
J. Ågren (2019). Notes on the LM-KTH quasigeoid and geoid computations. Report of the Joint Working Group 2.2.2 "The 1 cm geoid experiment", pp.1-5.