Digital terrain elevation models produced using radar altimetry and GPS data

Acquisition of any airborne geophysical data set involves two parameters: measurement of the actual signal being sought and definition of the position where each data observation is acquired. GPS provides accurate, estimates of the location of the sensor position relative to a defined ellipsoid. If at the same time one measures the distance from the observation platform to the surface of the Earth, using a radar altimeter, it is then possible to obtain an estimate of the elevation of the Earth´s surface at that point. By generating a grid image of discrete elevation data it is possible to produce a digital terrain elevation model (DTEM) of the survey area. Most aeromagnetic surveys comprise a series of flight lines and orthogonal tie-lines. With ideal data a second pass over the same location (either on the tie-line versus the flight-line, or even en a subsequent survey) should give the same elevation. However, attributes of the source data and characteristics of the terrain being modeled can significantly affect the accuracy of results. Comparing elevation data generated from two aeromagnetic surveys of the same area in Southern Alberta shows it is necessary to apply a series of corrections to elevation data just as one might with aeromagnetic data.