A comparison of radar altimetry and repeat pass interferometry as methods of producing digital terrain elevation models

Two methods used to produce digital terrain elevation models (DTEMs) are considered: radar altimetry and repeat-pass interferometry. In the case of the radar altimetry-derived DTEM, elevation values are obtained by subtracting aircraft altimeter measurements from GPS measurements of absolute aircraft height. Discrete elevation values are interpolated to form a continuous surface. Repeat-pass interferometry with RADARSAT-1 data is used to produce the second DTEM, which has then been georeferenced by means of ground control points. The two models are compared in terms of positional accuracy of terrain features and resolution of small-scale landforms. The interferometry-derived model is of higher resolution than the altimetry-derived model; this is expected based on the method of data collection. Positional discrepancies between terrain features are also identified. These discrepancies are attributed to the incidence angle of the RADARSAT-1 satellite relative to feature orientation. Georeferencing using control points is essential to the success of producing terrain models using repeat-pass interferometry.