Contribution of remote sensing to cartography (Application in the djanet area, east Hoggar, Algeria)

Abstract

The application of space techniques to geological studies is an important source of information for geological mapping. The optimal exploitation of high spatial resolution satellite imagery can contribute to the improvement of the geological map, particularly when it comes to mapping in arid and desert areas where outcrops are often inaccessible. Indeed, the region of Djanet, main object of our study, is characterized by rather important reliefs and this made the access difficult or sometimes even impossible in certain zones. The study area is located at the northeastern end of East Hoggar. It covers the terrane of Djanet and part of the terrane of Edembo. In addition, this region is probably one of the least explored areas of the Hoggar. This is why different remote sensing techniques have been used to make geological mapping faster and more efficient. The obtained images were subject to various treatments ranging from contrast enhancements to spectral enhancements, and using images in 742 RGB color compositions and calculation processing of bands (3/1, 5/4, 7/5) and the (5/7, 2/1, 4/2), Thus, the analysis of the processed Landsat-7 ETM + images from the Djanet area allowed us to establish a tele-analytical lithological map. The correlation of this map with the field data allowed us to check the validity and the correspondence of the different facies and especially to clarify the lithological contours derived from the analysis of Landsat satellite data.