Volume 7 ,2005

Enhanced False –Color Composite image from Landsat TM Spectral Bands 7,4,2 (RGB), showing a conspicuous sand dune field in the Western Desert of Egypt. It extends along the western margin of the Nile Valley between Asyut and Aswan. This field comprises longitudinal sand dunes trending NW-SE parallel to the prevailing wind direction. The Southeastern movement of these dunes represents a hazard to Lake Nasser

Integrating Remote Sensing, Image Processing and GIS Techniques for Developing a Model for Sand Fly Distribution and Risk Map

The aim of this study is to develop a GIS model based on applying an appropriate procedure for image processing techniques on satellite remote sensing data for mapping the spatial distribution of two types of sand flies (phlebotomus papatasi and phlebotomus bergeroti) in central arid southern Sinai. This study is divided into two phases; the first deals with image processing techniques for multispectral satellite data, including geometric correction, mosaicking, and enhancement using a high-pass filter for extracting information needed for the second phase. The second phase deals with model development for relating landscape variables characterizing flies' habitats and the corresponding information extracted from satellite data, as well as information from topographic, soil, and geologic maps. A risk map has been developed through relating the human activities and the spatial distribution of the considered species of sand flies using the designed logic model. Such a map provides guidance to disease control efforts and urbanization plans.

Comparative Study for The DEM Generation from Radarsat Stereoscopic Data and Topographic Maps

Radar satellite images could be used to produce digital elevation models (DEM) of certain areas by processing a couple of images, covering the same area, obtained at two different angles. In this study, the DEM generated from the Canadian RADARSAT stereoscopic data for a north western area of the Gulf of Suez, Egypt, is compared to the DEM generated from the topographic contour maps, scale 1:50,000. An evaluation and assessment of the results were conducted. The study shows that the DEM derived from RADARSAT data has a high precision as compared to the one generated from the topographic maps. It is also accurate enough to provide information where other sources of digital elevation are not available.

Use of Aster and Landsat Data in Mapping Land Use/ Land Cover and Soil Conditions in The Eastern Nile Delta, Egypt

The study area is located at northeastern part of the Nile Delta of Egypt, between latitudes 31°12'40" and 30°42'49" N, and longitudes 32°06'53" and 31°20'31"E, and it presents a promising area for both agricultural expansion and urban development. It covers an area of about 1031 Km2. Major activities in the area are running in relation with the installation of the eastern irrigation commands of EI- Salam Canal. Projects of fisheries and reclamation of saline soils dominate in the area. This study aims to test the recent satellite data obtained from new generation of space sensors (i.e. ASTER) in mapping land use/land cover. It is also desired to conclude the additional advantages of ASTER data over the conventional Landsat images.

In this study the ASTER image of May 2000 released by NASA Web Site, and Landsat ETM+ image, dated 2001, were used to map different classes of land use / land cover (LU/LC). The images were geometrically corrected, enhanced and classified on the basis of their spectral characteristics. The obtained enhanced and classified images were interpreted and validated by collection of soil and landscape data.

It was possible to identify 10 land use/ land cover classes from ASTER data and 8 classes from Landsat ETM+. The classes of "dried fish farms for land reclamation" and "fish farms and water bodies" nearly represent similar percentages in both LU/ LC maps. Fallow fields, halophytic plants and gypsiferous soils were accurately delineated from ASTER data, but were mixed with other classes in the Landsat ETM+ data. ASTER data permitted to separate 10.7% of study area as irrigated fields and shallow water bodies It was possible to delineate a zone of sandy deposits at the south of study area, however many of pivot irrigation systems were erected referring to reclamation of sandy soils. Spectral interference between saline soils and sandy deposits could be overcome by combining both types of data, thus multi sensor approach is recommended to handle spectral conflicts. Land suitability classification for 11 crops proved that the major limitations in the salt-affected soil are salinity, alkalinity and soil depth. The suitability limiting factors in newly reclaimed sandy soils include soil texture and depth. Predicted yield for wheat, corn and cotton in the northern part of study area are highly compared with the southern district. Also, the change detection revealed that serious environmental changes have occurred in the study area, mainly due to the dryness of some parts of Manzala Lagoon for land reclamation purposes. It could be concluded that ASTER data is a powerful tool for operational monitoring of land use / land cover, comparing with Landsat one.

Terrain Analyses and Soil Characteristics as a Base for Land Capability Assessment of Arable Lands, Sinai, Egypt

The present study aimed at analyzing some terrains of Sinai Peninsula to identify soil characteristics and their capability. Integration of Remote Sensing (RS) and Geographic Information Systems (GIS) provides convenient tools for terrain analyses and soil types recognition. Terrain analyses, including contour, hillshade, slope and aspect, were performed to be raster inputs for Cervatana land capability model. On the other hand, soil characteristics represented by the main physical and chemical properties as well as soil morphological description were used for two purposes: (a) as model inputs and (b) to identify, with other parameters, soil taxonomic groups of the Peninsula. Fifteen geomorphologic and their associated soil units have been identified as follows: Flood plains, Coastal plains, Sand beaches, Decantation basins, Aeolian sand strips, Dry valleys, Pediplains , Evaporites, Sand dune areas, Wet and dry sabkhas, Outwash plains, Old river terraces, Sandy plain, Alluvial fans and Footslopes. Additional twelve miscellaneous geomorphologic units with no developed soils were recognized. Seven soil taxonomic great groups were identified i.e. Typic Haplocalcids, Typic Aquisalids, Typic Torrifluvents, Typic Torripasmments, Typic Calcigypsids, Calcic Aquisalids, and Lithic Torripasmments. Land capability classes using Cervatana model were represented by S2, S3 and N.

Geomorphology of the Area Southeast of Aswan, Egypt

The use of Remote Sensing and GIS techniques enables the geomorphologic analysis of the area of southeast Aswan, by preparing a geomorphologic map and performing a morphometric analysis of the surface drainage basins, to evaluate their flash flood hazards. A preliminary land-use map for the study area has been suggested. The main identified landforms are structurally controlled plateaus including three types (plateaus with dense drainage lines, plateaus with highly eroded surfaces and plateaus covered with ferruginous sandstone). Structurally controlled features also include cuestas and tors. Landforms of volcanic origin are present as circular features (ring complexes), lava sheets, cones and igneous dykes. Landforms of fluvial origin are expressed as dry valleys, badlands, alluvial fans, terraces and wadi deposits. Landforms of aeolian origin are represented by longitudinal sand dunes and sand sheets. The surface drainage net is, to a large extent, structurally controlled and displays dendritic and rectangular patterns. Analysis of thirty surface drainage basins in the study area enables the construction of a flash flood risk map showing highly, moderately and low hazardous basins. A preliminary land-use map is presented with four main categories (1 through 4). Category 1 is the best site for development in low-lying areas in the mouth of basins with low flash flood hazard and Category 4 is the least suitable for development and includes areas situated on the top of plateaus or highlands, or in areas covered by tors.

Monitoring of Sand Dunes Migration for Developing Mitigative Measures in El-kharga Depression, Western Desert, Egypt

Sand dunes cover extensive areas over El-Kharga Depression in the Western Desert of Egypt. Sand dunes encroachment represents the main natural hazard for development projects. This study aims at monitoring sand dunes movements using high resolution satellite imagery at different dates. Detection of rates of movement and pathway of sand dunes migration could help in understanding the most critical controls on dunes movement in El-Kharga Depression.

The southern part of Ghard Abu Muharik is the main source of sand that form the dunes in El-Kharga Depression and the southern sand sheets. This sand is transported in parallel belts, along the depression and the surrounding plateaux without end point. The dunes within belts move at different rates in a southeasterly to southerly pathways controlled by the prevailing wind direction, corridors and local relief. These belts virtually do not shift laterally or advance down the prevailing wind, reflecting consistency of sand supply from source areas. The wind regime, local relief and geological structures play major role in eolian sand dynamics, but the source sediment availability could be more important than climate controls.

Monitoring the directions of the dunes migration and detection of the movement rates are important in management of mitigative measures and detection of immune sites for development projects, as well as selection of suitable paths for alternative roads crossing active dune belts. Using multi-temporal satellite images from Landsat satellite resulted in an accurate and reasonable movement rate and direction which has been calculated to be about 8 m/y in the southward direction.

Discrimination of Basement Rocks and Alteration Zones in Shalatein Area, Southeastern Egypt, Using Landsat TM Imagery Data

The Shalatein area, in the southeastern corner of Egypt, is occupied by metamorphic and intrusive Precambrian basement assemblages nonconformably overlain by Cretaceous sandstones. Both Precambrian and Cretaceous rocks are extruded by Tertiary basalts. The metamorphic rocks comprise dismembered ophiolitic serpentinites and calc-alkaline metavolcanics with their related pyroclastics, while the intrusive rocks include syn-tectonic tonalite-granodiorite (G1) and late tectonic intrusions which are represented by ultramafic-mafic rocks and monzogranite-alkali feldspar granite (G2).

Landsat Thematic Mapper (TM) imagery data was digitally processed where geometric corrections, radiometric balancing, contrast stretching and ratioing techniques were applied. To get the accurate discrimination of the encountered basement rocks and the mineralized alteration zones, their spectral signature profiles were delineated in different bands and band ratios using the data of both Landsat TM and false colour composite ratio images. The study revealed that the false colour composite ratio image (5/1, 5/7, 5/4*3/4) is the best to discriminate the different basement rocks and to detect the mineralized alteration zones hosted within Wadi Beida sheared metavolcanics.

Utilization of Landsat-7 ETM+ and SIR-C/X SAR Data for Mapping the Basaltic Rocks and their Alteration Products, Gebel Qatrani–6th October District, North Western Desert, Egypt

Landsat- 7 ETM+ imagery and SIR-C/X SAR radar data were used to recognize the spectral characteristics, as well as the surface roughness of the basaltic sheets at Gebel Qatrani-6th October district, North Western Desert, Egypt. Band ratios generated from the reflectance images and speckle filter are the main procedures carried throughout this research. Based on the variance and standard deviation of the band ratios the following ratios (4/3, 7/1 and 4/5) were selected to differentiate between the fresh and altered basalts over the study area. The basaltic sheets at Gebel Qatrani-6th October district are dark on the 7/1 and the 4/3 band ratio images and bright on the 4/5 band ratio image. The low 4/3 value is attributed to the presence of absorption features around the band 4 wavelength region related to the abundance of pyroxene crystals. The modal analysis of the altered basalt at Gebel Qatrani revealed that the alteration products (chlorite, illite and montmorillonite) amount up to 21 % per vol. On the false color composite ratio image (4/3: R; 7/1: G; and 4/5: B), the altered basalt has low 7/1 reflectance values and high 4/5 and 4/3 reflectance values. The low 7/1 value is attributed to the presence of absorption features around the band 7 wavelength region related to the abundance of alteration products and calcite that fills the amygdales. The false-color composite ratio image 4/3: R; 7/1: G; and 4/5: B; was merged using IRS transform method with the panchromatic band (15 meters spatial resolution) to generate an 1:50 000 image map for the study area. The 6th October-El-Sheikh Zayed basalts with smooth surface scatter the radar return away from the radar sensor and appear to have a dark image signature on SIR-C/X SAR radar image. On the contrary, the Gebel Qatrani basalts possess a relatively rough surface and thus, scatter radar signal back to the detector and hence appear bright on the radar imagery.