| 1. |
- Ardö, J., et al.
(författare)
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On the accuracy of the global positioning system-a test using a hand-held receiver
- 1992
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Ingår i: International Journal of Remote Sensing. - : Informa UK Limited. - 0143-1161 .- 1366-5901. ; 13:16, s. 3229-3233
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Tidskriftsartikel (refereegranskat)abstract
- This study aims to evaluate the accuracy of location (x, y and z) using a Magellan GPS NAV 1000 receiver. The position of a known reference point was compared with 50 fix points measured in two-dimensional (2D) mode (x, y) and with 50 fix points measured in three-dimensional (3D) mode (x, y and z). The mean errors and the root mean square errors (RMSE) in the Euclidian distances between the reference poinl and the measured fix points were 17.9m and 20.0m respectively for the 2D measurements, and 25.7m and 34.8m respectively for the 3D measurements. The mean error in elevation was 0-2 m and the corresponding RMSE was 39.1 m. The study indicates a significant difference in the total error (Euclidian distance) between points obtained with different signal qualities and different geometric qualities. The error in the Euclidian distance never exceeded 44.0 m using 2D mode, which suggests that the Magellan GPS NAV 1000 receiver should be a useful supportive tool for many remote sensing applications.
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| 2. |
- Larsson, Helena, et al.
(författare)
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Remote sensing for forest management in semi-arid environments
- 1990
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Ingår i: Proceedings of the International Symposium on Remote Sensing of Environment. ; 1, s. 573-580
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Konferensbidrag (refereegranskat)abstract
- The aim of the study is to (i) evaluate a method, based on the normalized difference vegetation index (NDVI) calculated from Landsat TM data, for estimation of tree canopy cover in semi-arid environments and (ii) determine canopy cover changes in a forest area in the Sudan by applying the method on Landsat MSS data from 1972 and 1979. Primarily, the NDVI based method was applied on NDVI values, calculated from corrected Landsat TM scene from 1987. The output of the applied model was a continuous canopy cover map. The result was compared to field data from 1989. The total accuracy is above 70 per cent for the classified areas. To determine canopy cover changes from 1972 to 1987 the Landsat TM scene was complemented by two Landsat MSS scenes from 1972 and 1979. The same regression model as in the first part of the study was applied on the scenes. Between 1972 and 1979 an increase, from 60 per cent to 76 per cent, in mean canopy cover was determined. In 1987 the mean canopy cover was only 16 per cent.
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