Artificial satellites play an important role in different fields of surveying. These satellites are used for taking images of any area on the earth with different spatial resolution and different wave length. This research presents a study for using different types of satellite images such as SRTM-three arc second, ASTER-one arc second, and Google Erath satellite image (Geoeye-1) to obtain the best source for extracting streams network in Egypt. The mathematical model which, is used in this research was the "Regression analysis" model. The streams network were extracted using DTM with SRTM and ASTER which based on automatic extraction and Google Erath satellite image (Geoeye-1) with topographic map at scale 1: 25000 based on manual extraction. The regression analysis (R) and RMS for the extracted streams network were computed for each source (SRTM, ASTER and GeoEye-1). Theoretically, it is known that when the values of R ≈ 1 and less RMS the best results. The results shows that the values of R and RMS for streams network were 0.993, 77.73 m for ASTER, 0.996, 62.08 m for SRTM and 0.999, 33.42 for Google satellite image. These results indicate that the best source was Google Erath satellite image (Geoeye-1) compared with the topographic map, but Google earth didn’t have the same spatial resolution for all areas. SRTM of free download for the whole globe gives result close from that of Google Earth satellite image (Geoeye-1) followed by ASTER. |
