Distribution Of SRTM Error Across China

The SRTM larc (～90m) data has been widely used in the Geographic Research since its first version published in 2003, however the quality of SRTM data is one of the most important issues that should be considered. In this thesis, the magnitude of the elevation error and its distribution in the data from the Shuttle Radar Topography Mission (SRTM) over the continent and main islands of China and its association with topographic and land cover factors were systematically evaluated. Based on spatial registration, landscape features were extracted from more than 500,000 sites from different datasets across China to determine the pattern of variation in the error under different landscape characteristics through single factor analysis. The results showed that the elevation, slope and aspect data from the SRTM could well represent the topographic attributes in various terrains of China. The mean elevation error of the entire sample was-0.35m, and the 90% error was 7.4m, which attained the absolute error specification of 16 m of SRTM. However, there was extensive and observable but low proportion of areas with anomalies in the SRTM data. Slope was the key factor affecting elevation error and also affected the pattern of the variation of error in other land-scape features. The elevation error changed from positive to negative, and the absolute error, up to a maximum of-0.86m, generally rose with increasing slope. The positive errors were concentrated along the northerly aspect within 315° to 360° and 0° to 45°, whereas the negative errors were concentrated along the westerly and southwesterly aspects within 45° to 315°. In flat areas less affected by slope, the mean elevation errors due to the vegetation cover ranged from 0.15m to 1.67m, and the magnitude of the standard deviation gradually increased with increasing slope and vegetation coverage. The mean errors were negative in glaciers, deserts and wetlands, and the magnitude was-1.05m,-2.03m,-2.43m respectively. In contrast, the mean error of the built-up urban areas was positive with a magnitude greater than lm. In general, because of the complex topography and various land cover types, the elevation error in the SRTM data resulted in a complex pattern of variation over China.