| The local geoid in a test area in the Canadian Rocky Mountains is computed using airborne gravimetry data. The geoid is computed by using the vertical and horizontal components (VC and HC) of the gravity disturbance vector. In addition, the combination of the three components by least squares collocation (LSC) is done. The use of crossovers to estimate biases and trends in the gravity signals, and the use of minimal control as constraints in the crossover adjustment are studied. Moreover, the downward continuation and direct and indirect effects due to removal and restoration of masses are investigated. An expression for the effect of the masses applied to disturbing potential is provided.;Geoid estimates coming from VC and HC, computed using Hotine's and line integral, show the same level of accuracy when compared to the Canadian geoid. Relative accuracies on the order of 3 to 7 cm for the VC geoid, and of 4 to 12 cm for the HC geoid are achieved. The VC geoid suffers from edge effects on the results, while the HC geoid is highly dependent on ground control.;Regarding the estimation of the geoid by LSC, using the three components of the gravity disturbance vector (3C-LSC), we observe differences in the range of 4 to 6 cm, with respect to the Canadian geoid. Comparing the 3C-LSC geoid with the VC geoid using Hotine's integral, the 3C-LSC are comparable and improved for some lines. In general the result from the 3C-LSC are better than those from HC, by line integral. On the other hand, the use of only the vertical component by least squares collocation (VC-LSC) provides, in general, better results than those from 3C-LSC, and those from the VC and HC by the use of Hotine's and line integral. We could expect better results for the case of 3C-LSC if we are able to improve the quality of the measured horizontal components of the gravity disturbance vector.;The application of a wave correlation filter to both HC and VC geoids show promising results for the improvement of the accuracy of the combined geoid. |
