False Color Composite Image Research Articles

Mapping of hydrothermal alteration in the upper mantle-lower crust transition zone of the Tayin Massif, Sultanate of Oman using remote sensing technique

This study maps hydrothermal alteration of Wadi Tayin Massif of the Sultanate of Oman using the spectral bands of Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and the image processing methods namely band ratios, false color composite (FCC), spectral angle mapper (SAM), mixture tuned matched filtering (MTMF) and linear spectral unmixing (LSU) to understand alteration of the upper mantle-lower crust transition zone. The study of FCC image of the spectral bands 8, 4, and 1 in Red (R), Green (G), and Blue (B), respectively, showed the presence of the hydrothermal alteration in shades of purple and brown over the mantle peridotites, dunites, and crustal gabbros. The ASTER band ratios R:9/8, G:4/3, B:2/1 used in this study able to show the occurrence and distribution of alteration in orange distinctly. The SAM, LSU and MTMF image processing methods applied over the region confirmed the presence of alteration and altered minerals in the rocks. The assessment of accuracy for the methods provided the high accuracy of 91.86% and Kappa Coefficient = 0.89 in the LSU method. The image interpretations are studied in the field and the occurrence of alterations are validated by presence of strong serpentinization in the peridotites and dunites, and secondary veins in the micro cracks of gabbros. Laboratory studies showed presence of the serpentinization, iddingsitization, chloritization and development of pargasite in the altered rocks. This study shows application of the ASTER sensor to map hydrothermal alteration found near the fast-spreading oceanic ridge.

DELINEATION AND MAPPING OF ALLUVIAL FANS BY THE USE OF LANDSAT/TM AND TERRA/ASTER SATELLITE IMAGES.

The purpose of the study was the precise delineation and mapping of alluvial fans, locating in mountainous areas of Northern Greece, by the use of: a) LANDSAT/TM and TERRA/ASTER satellite images (pixel size 30 m and 15-90 m respectively), b) topographic and geological maps and c) ground truth procedure (visiting the test sites). The digital processing of the satellite images was performed with EASI/PACE software. False Colour Composite (FCC) images, that helped to the better delineation of the fans, were derived by various image processing techniques, such as contrast stretching, ratioing, Principal Components Analysis (PCA),etc. The above processed images were imported into a Geographical Information System (GIS) and they were georeferenced to UTM Projection System. Next, the delineated (on the images) fans were digitized and overlaid to topographic and geological maps. From the above procedure and in comparison to ground-truth observations, it was concluded that the boundaries of the alluvial fans appear more precisely on the satellite images than in geological and topographic maps. The results of this study could be useful to geomorphologists dealing with morphological study and analysis of the alluvial fans. Also, they could be helpful to the improvement and updating of the present geological maps, by defining the boundaries of the fans mere precisely. Finally, conclusions can be drawn concerning the sorting of the materials comprising the fans. This information could be useful to hydrogeologists, since the alluvial fans are usually rich in water content.

Analytic signal, depth and multispectral interpretation of areas within the Continental Terminal, North-western Nigeria

This study utilized the ability of remote sensing and aeromagnetic data of the Continental Terminal, Northwestern Nigeria, to accentuate structural and lithological geologic features as well as depth estimation and mineral potential for exploitation purposes. The analytic signal and source parameter imaging filtering techniques on the magnetic data helped to identify causative magnetic bodies and space-depth relationship, two important indices in regional and ore body modelling. Depth interpretation result ranged from 120m to 2000m in the entire regolith cover where the basement rocks are overlain by clastic materials. Areas of deeper depths coincided well with regions of higher magnetic anomalies while areas of shallow depth coincided well with regions of lower magnetic anomalies with magnetic values ranging from 33121nT to 32980nT suggestive of a likelihood of having the magnetic unit of the basement at the top of the basement surface. The study identified the structural trend from the aeromagnetic map, showing a perfect agreement with the geologic map and Landsat-8 imagery. The Landsat-8 data was used for structural and lithological mapping and in general geological interpretation. Single band combination of 764 representing Red, Green and Blue were processed from the false colour composite image and pan-sharpened using the pan chromatic band to enhance structural features on the map. The study area showed no promise of hydrocarbon accumulation from the structural interpretation for economic benefits. However, economic-grade minerals were inferred due to magnetic anomalies that suggested accumulation of magnetic materials located within the proximity of lineaments.

Comparative Analysis of Potentials of ASTER Thermal Infrared Band Derived Emissivity Composite, Radiance Composite and Emissivity–Temperature Composite in Geological Mapping of Proterozoic Rocks in Parts of Banswara, Rajasthan

In this study, we have compared the potential utility of relative emissivity bands derived from Level 1B (at sensor georectified radiance) and Level 2 (multiband emissivity product provided by ASTER service provider) data products of Advanced Space-borne Thermal Emission and Reflection Radiometer (ASTER) sensor for delineating different geological units of volcano-sedimentary provinces in parts Banswara, Rajasthan. Reference channel method was used for deriving emissivity from Level 1B data whereas temperature emissivity separation algorithm was used to derive Level 2 emissivity data products. In the false colour composite image of emissivity bands of two different data products, quartzite was enhanced but other rocks were not discernible. On the other hand, other rocks of the study area were detectable (basalt, gneiss, dolomitic marble) in Level 1B radiance data. In radiance image, variations in surface temperature and emissivity were recorded and this was helpful for delineating different rocks. Surface temperature is sensitive to land cover, moisture and it helped in detecting rocks like dolomite which was covered with moisture rich soil and vegetation. Similarly, emissivity–temperature composite was also proved useful in delineating basalt, quartzite (chloritic), dolomite/dolomitic marble and associated gneiss/migmatites as it brought out the contrast of composition and the differences in the thermophysical parameters resulted temperature variation. An image composite prepared using emissivity band 13, ratio band derived using emissivity band 12 and band 11 and radiant temperature band also could delineate all the major rock types. Further, scatter plots of emissivity bands and temperature used for clustering of different rock units could delineate these rocks from each other. Therefore, conjugate composite images of emissivity and radiant temperature was suitable in delineating all the rocks than the emissivity composite images of different types.

Discrimination of bedrocks and landslide area of Jabal Samhan – Zalawt Plain region of the southern Oman using remote sensing technique

This study discriminates bedrocks, landslides region and land slid materials (rock falls and debris) of previous landslides occurred along the Radhuma escarpment of the Jabal Samhan Mountain – Zalawt plain, southern Oman. We used spectral bands of ASTER, and PCA and SAM image processing methods to understand the occurrence and spatial distribution of landslides of the region. The study of false color composite image (R:8; G:3; B1) of ASTER showed the occurrence of thin shale intercalation at the top of massive bioclastic limestone formation in the Jabal Samhan Mountain. The developed principal components image (PC1, PC2 and PC6) discriminated well the occurrence of landslides area and land slid materials over Mirbat formations of the Zalawt plain along the Radhuma escarpment. The SAM method detected minerals of the bedrocks and land slid materials, and showed their occurrences and distributions. The Radhuma escarpment is studied using ASTER global digital elevation map (GDEM). Study of drainage, relief, geomorphology and structure of the region showed that the wadi drainages are flowing in trellis and dendritic patterns with anti-directions over the mountains and plains region. Interpretation of geomorphological units of the region exhibited the occurrence of slope pediments along the escarpment. The presence of major structures namely Sala Afan Graben, extensional fractures and tensional joints in the Tertiary formations of Jabal Samhan are studied over the images. All results are verified and confirmed through field studies.

Automatic near real-time flood detection using Suomi-NPP/VIIRS data

Near real-time satellite-derived flood maps are invaluable to river forecasters and decision-makers for disaster monitoring and relief efforts. With support from the JPSS (Joint Polar Satellite System) Proving Ground and Risk Reduction (PGRR) Program, flood detection software has been developed using Suomi-NPP/VIIRS (Suomi National Polar-orbiting Partnership/Visible Infrared Imaging Radiometer Suite) imagery to automatically generate near real-time flood maps for National Weather Service (NWS) River Forecast Centers (RFC) in the USA. The software, which is called VIIRS NOAA GMU Flood Version 1.0 (hereafter referred to as VNG Flood V1.0), consists of a series of algorithms that include water detection, cloud shadow removal, terrain shadow removal, minor flood detection, water fraction retrieval, and floodwater determination. The software is designed for flood detection in any land region between 80°S and 80°N, and it has been running routinely with direct broadcast SNPP/VIIRS data at the Space Science and Engineering Center at the University of Wisconsin-Madison (UW/SSEC) and the Geographic Information Network of Alaska at the University of Alaska-Fairbanks (UAF/GINA) since 2014. Near real-time flood maps are distributed via the Unidata Local Data Manager (LDM), reviewed by river forecasters in AWIPS-II (the second generation of the Advanced Weather Interactive Processing System) and applied in flood operations. Initial feedback from operational forecasters on the product accuracy and performance has been largely positive. The software capability has also been extended to areas outside of the USA via a case-driven mode to detect major floods all over the world. Offline evaluation efforts include the visual inspection of over 10,000 VIIRS false-color composite images, an inter-comparison with MODIS automatic flood products and a quantitative validation using Landsat imagery. The steady performance from the 3-year routine process and the promising evaluation results indicate that VNG Flood V1.0 has a high feasibility for flood detection at the product level.

Evaporite mineral mapping and determining their source rocks using remote sensing data in Sirjan playa, Kerman, Iran

In this research, evaporite minerals of Sirjan playa, Iran were mapped using Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and Landsat 8 images. Spectral angle mapper (SAM) was applied to map evaporite minerals of the study area. Two kinds of reference spectra were used for classifying the images that consist of: (1) recorded reflectance spectra of evaporite minerals and (2) image-derived spectra which were acquired from images based on GPS coordinates of samples. Determination of evaporite minerals assessed by X-ray diffraction (XRD) on field samples which were collected in October 2015 when the lake was completely dry. After image classification, the overall accuracy of 95.27% for Landsat 8 images and 91.81% for ASTER images were achieved, respectively, using image-derived spectra. SAM classification using samples’ spectra showed lower accuracy of 85.96 and 80.31% for ASTER and Landsat images, respectively. Therefore, the image-derived spectra produced better classification accuracy. For determining the main source of inflows of the sediments into the playa, drainage system of Sirjan basin, that was derived using digital elevation model, false color composite image, mosaic of old aerial photographs and map of evaporite minerals were used. It showed that the main source of inflows of the sediments to the playa is from volcanic and sedimentary rocks of Urumieh-Dokhtar mountains located in the north-east and eastern parts of the playa.

Archaeological Exploration in Srirangapatna and Its Environ Through Remote Sensing Analysis

This study involves exploration of archaeological structures in Srirangapatana and virtual reconstruction of Srirangapatana fort using geo-spatial techniques. Antiquity of this river island town goes back to ninth century AD which continued till British rule and hence has abundance of archaeological structures on it. Some of these structures are known and well-maintained while others are unprotected, unexcavated, hidden under thick vegetation or forgotten. To identify archaeological features such as buried/dilapidated/vegetation infested structures/features on ground, we used high resolution multispectral remote sensing data (0.5 and 5.6 m), Cartosat 1 stereo pairs (2.5 m), anaglyphs, historical documents, and analysed them on GIS platform. This study enabled us to: trace the concentric moats and fort-wall by using false colour composite image together with anaglyphs generated from Cartosat 1 stereo pair; explore hitherto unexplored and unexcavated archaeological features; identify unknown and abandoned temples/structures smothered with wild vegetation; locate exact location of currently non-existent site mentioned in historical records; identify the location of buried canal. This study also demonstrates how methodic use of various interpretation keys, image processing and analysis (such as NDVI, DEM, anaglyphs) can help in extracting archaeological features and direct archaeologists for further exploration.

Identification of Rocks and Their Quartz Content in Gua Musang Goldfield Using Advanced Spaceborne Thermal Emission and Reflection Radiometer Imagery

Quartz is an important mineral element and the most abundant rock-forming mineral that controls the mineralogy of a reservoir. At the surface, quartz is more stable than most other rock minerals because it is made up of interlocking silica that makes it quite resistant to mechanical weathering. Quartz abundance is an indication of mineralization in many metal deposits; therefore, identification and mapping of quartz in rocks are of great value for exploration and resource potential assessments. In this study, thermal infrared (TIR) bands of the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) imagery were used to identify quartz contained rocks in Gua Musang. First, the image was corrected for atmospheric effect and the study area subset for further processing. Thereafter, spectral transformation (principal component analysis (PCA)) was implemented on the TIR bands and the resulting principal component (PC) images were analysed. The three optimal PCs were selected using the strength of spectral interaction and the eigenvalues of each band. To discriminate between quartz-rich and quartz-poor rocks, RGB false colour composite and greyscale image of one of the PCs were analysed. The result shows that volcanogenic igneous rock and carbonate sedimentary rocks of Permian formation are quartz-poor while Triassic sedimentary rock made up of organic particles and sandstone is quartz-rich. On the contrary, the quartz content in the metamorphic rock varies across the area but is richer in quartz content than the igneous and carbonate rocks. Classification of the composite image classified using maximum likelihood (ML) supervised classification method produced overall accuracy and Kappa coefficient of 96.53%, and 0.95, respectively.

Identifying Alluvial fans features using multispectral image processing techniques in selected area, northern Iraq

Landsat 7 Enhanced Thematic Mapper Plus image data was used to identify and map alluvial fans features in Shaikh Ibrahim anticline northern Iraq. In the present study, an active flowchart was design to extract and determine alluvial fans using digital image processing operations and digital elevation analysis. Two image processing methods including (image transformation and image enhancement) were used. Image transformation including principal component analysis (PCA) and ratio images (RI) analysis, while image enhancement operation including false color composite images (FCC). In image transformation processing, Based on the detailed analysis of eigenvectors and eigenvalues derived from different combinations of (PCA), five (PC) images of bands (13457) have been extracted and –PC4 has relatively strong positive loading for band 5 (0.632166) and high negative loading for band 7 (-0.369417) consequently, PC4 was given effective delineation about the major alluvial fans at the southwestern footslope from Shaikh Ibrahim anticline. In ratio image analysis, A combination of (RI) based on the spectral characteristics of alluvial fans materials were selected. Image enhancement includes A false color image of the subscene was produced by assigning band (741). This color composite was found to be useful in emphasizing to the all materials of alluvial fans. Digital elevation models (DEM) were used for describing topographic features related to the alluvial fans.

A Biophysical Image Compositing Technique for the Global-Scale Extraction and Mapping of Barren Lands

As the barren lands play a key role in the interaction between land cover dynamics and climate system, an efficient methodology for the global-scale extraction and mapping of the barren lands is important. The discriminative potential of the existing soil/bareness indexes was assessed by collecting globally distributed reference data belonging to major land cover types. The existing soil/bareness indexes parameterized at the local scale did not work satisfactorily everywhere at the global level. A new technique called the Biophysical Image Composite (BIC) is proposed in the research by exploiting time-series of the multi-spectral data to capture global-scale barren land attributes effectively. The BIC is a false color composite image made up of Normalized Difference Vegetation Index (NDVI), short wave infrared reflectance, and green reflectance, which were specially selected from the highest vegetation activity period by avoiding signals from the seasonal snowfall. The drastic contrast between the barren lands and vegetation as exhibited by the BIC provides a robust extraction and mapping of the barren lands, and facilitates its visual interpretation. Random Forests based supervised classification approach was applied on the BIC for the mapping of global barren lands. A new global barren land cover map of year 2013 was produced with high accuracy. The comparison of the resulted map with an existing map of the same year showed a substantial discrepancy between two maps due to methodological variation. To cope with this problem, the BIC based mapping methodology, with a special account of the land surface phenological changes, is suggested to standardize the global-scale estimates and mapping of the barren lands.

UTILIZATION OF LANDSAT-8 DATA FOR LITHOLOGICAL MAPPING OF BASEMENT ROCKS OF PLATEAU STATE NORTH CENTRAL NIGERIA

Abstract. This paper utilized the Landsat-8 image data to map the lithology’s of Plateau state north central Nigeria. This is includes the rocks, with particular emphasis on their description and classification. We are living in geologic times and sciences that provide adequate knowledge of the natures of what we live on so as to preserve and have means of sustaining human life. Plateau State is covered by four scenes of Landsat Data, and to describe the lithology’s, each scene was processed to produce images. Two different false colour composite images of Landsat-8 (FCC 7, 5 and 3 and BR composites) in RGB were generated and used for the production of 1:100,000 geological map of the study area. The identification of predominant biotitic granitic rocks was revealed and that are distributed along the Jos-Bukuru complex and underlying almost half of the entire state. Moreover, the other rock complexes such as basalts and rhyolites volcanic rocks were also discriminated. This study indicates that Landsat-8 image data has great capability to discriminate lithological units and the production of up-to-date geological maps at regional scale and could be applicable in other regions of the African continent.

Utilization of ETM+ Landsat data in geologic mapping of wadi Ghadir-Gabal Zabara area, Central Eastern Desert, Egypt

The Wadi Ghadir area, Central Eastern Desert, Egypt is covered by a sequence of Pan-African basement rocks comprising allochthonous ophiolitic rock assemblage thrust over Gabal Zabara gneiss. The ophiolite sequence comprises layered gabbro, pillowed basalts, island arc metavolcanics and low grade metasediments. These rocks are intruded by syn-to late tectonic intrusions followed by basic and acidic dyke swarms. The processed digital data of Landsat 7 ETM+ covering the study area have been used. Several products of Landsat-7 ETM+ digital data such as true color image (3, 2 and 1 in RGB), false color composite images (7, 4, 2 and 7, 5, 1 in RGB), principal component (PC2, PC1, PC4), band rationing images (5/1, 3/2, 7/2), (5/3, 4/2, 3/1) and (3/1, 4/2, 5/7) are generated. Products of image processing improve lithological discrimination specially of serpentinites talc carbonate rocks and different varieties of intrusive rocks. Supervised and unsupervised classifications have been used to recognize and discriminate between the different rock units.The obvious color contrast of ratio images enabled easier delineation of major structural features characterizing the mapped area. NNW-SSE striking, easterly dipping, thrust faults are located in the western part within the study area. They are associated with asymmetrical folds whose axial planes are parallel to these thrusts. Other NW folds affecting gabbro masses and mélange rocks could easily be delineated and verified during field observations. Two sets of shear zones of NW and NE trends affect the mapped area. Lineament analysis revealed the prevalence of two main structural trends NW-SE and NE-SW.

Signature capture of red soil patches and their acidity-A case study of Banka district, Bihar, India

Colour in soils as well as other object is the visual perceptual property which is perceived by human eye. They are governed by spectrum of light corresponding to wavelength or reflected energy of the material. Developed model for soil acidity is based on visual interpretation, principal component and spectral enhancement techniques by using of the satellite image (IRS LISS III, 2014). In this context, red soil patch is much sensitive in red spectral band comparison to green and blue spectral bands and perceived as red tone by human eyes but same soil patch appears green in false colour composite (FCC) image of NIR (0.70-0.80?m), Red (0.60-0.70 ?m) and Green (0.50-0.60?m) bands. The maximum coverage of red soil patches having low pH < 6.5 (1:2.5) was recognized in 44.07 per cent of the total geographical area (3019.56 sq.km) under Banka district. Maximum red soil patches having their acidity were recognised in Katoria (18.56%), Chanan (15.15%), Bounsi (10.44%) and Banka (9.92%) blocks. Overall results indicated that variation of tone in different bands helps for the separation of red soil patches.

New ASTER derived thermal indices to delineate mineralogy of different granitoids of an Archaean Craton and analysis of their potentials with reference to Ninomiya's indices for delineating quartz and mafic minerals of granitoids—An analysis in Dharwar Craton, India

We processed five thermal infrared (TIR) bands of Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) “at-sensor radiance” (Level 1B) data to derive few new indices to delineate variation in quartz, feldspar and mafic minerals in three different variants of granitoid; commonly occurring quartz bearing intrusive rock group. In this regard, three indices named as quartz-bearing rock index (QRI), feldspar-bearing rock index (FRI) and mafic-bearing rock index(MRI) were proposed.QRI index was derived using band 10, band 12 and band 13((band 10/band 12)∗(band 13/band 12)) of ASTER radiance image. MRI index was derived using band 12, band 13 and band 14 ((band 12/band 13)∗(band 13/band 14)) of ASTER radiance bands while band 10, band 11 were combined to derive FRI ((band 10/band 11) index. Three indices were combined in false colour composite image (FCC) and three-dimensional scatter plot to delineate granite, alkali granite and mafic rich granodioritic gneiss from each other as these granitoids had variable abundances of quartz, feldspar and mafic minerals. QRI and MRI were compared with the corresponding quartz and mafic indices proposed by Ninomiya (2005). It was observed from the respective ratio images and their regression plots that MRI and Ninomiya's mafic index (NMI) were complementary to each other. On the other hand, QRI image was better in enhancing quartz enrichment in alkali granites than Ninomiya's quartz index (NQI).However, QRI index was comparable with the quartz index proposed by Rockwall and Hofstra (2008) in terms of delineating quartz enrichment in alkali granite. Mutual exclusive nature of mafic minerals and quartz in granitoids was also evident from the negative correlation between MRI and QRI indices of the granitoids. On the other hand, FRI and QRI were negatively correlated with low regression value. This was resulted due to the combined effect of inverse relation of abundance of two dominant feldspars with quartz in different granitoids. In granitoids, abundance of plagioclase is known to increase with decreasing quartz content in granodiorite and tonalite although alkali feldspar bearing granites are characterised with high silica content. Results of discrimination of granitoids using proposed indices were validated based on deriving emissivity spectra of rocks and comparing them with ASTER TIR band resampled laboratory spectra of respective granitoids in addition to use geological map of the study area. Emissivity spectra of granitoids were derived from emissivity image (derived using emissivity normalisation method) after geospatially tagging it with QRI–FRI–MRI image composite; which was used to delineate exposures of granitoids. Further, we also found that the QRI, MRI and FRI indices had poor temperature dependence; when these indices were compared with relative surface temperature image derived from radiance bands using emissivity normalisation algorithm. Therefore, proposed indices can be implemented for delineating mineralogical variations of granitoids irrespective of surface temperature condition. Hence, proposed indices may be used successfully to delineate different granitic intrusions and relating their mineralogical variations with metallogeny.

Improved Land-use/Land-cover classification of semi-arid deciduous forest landscape using thermal remote sensing

Land Use Land Cover (LULC) change detection helps the policy makers to understand the environmental change dynamics to ensure sustainable development. Hence, LULC feature identification has emerged as an important research aspect and thus, a proper and accurate methodology for LULC classification is the need of time. In this study, Landsat-7 satellite data captured by Enhanced Thematic Mapper (ETM+) were used for LULC classification employing the maximum likelihood supervised classification (MLC) algorithm. The study targets the improvement of classification accuracy with the combined use of thermal and spectral information from satellite imagery. Land surface temperature (LST) is sensitive to land surface features and hence can be used to extract information on LULC features. The classification accuracy was found to improve on integrating the thermal information from the thermal band of Landsat ETM+ with spectral information. Two thermal vegetation indices, namely Thermal Integrated Vegetation Index (TLIVI) and Advanced Thermal Integrated Vegetation Index (ATLIVI), proposed in this study showed fairly good correlations (R2=0.65 and 0.7, respectively) with the derived surface temperature. These indices based on empirical parameterization of the relationship between surface temperature (Ts) and vegetation indices showed an increase of nearly 6% in the overall accuracy for land-use/land-cover (LULC) classification in comparison to MLC algorithm using Standard False Colour Composite (FCC) satellite image of Landsat ETM+ as reference.

Integrated approach of using ASTER-derived emissivity and pixel temperature for delineating different granitoids – a case study in parts of Dharwar Craton, India

We have delineated different granitoids based on variation in emissivity and relative surface temperature recorded in thermal bands of Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) sensor of EO-1 satellite. In this regard, we have used emissivity normalization algorithm to derive broadband emissivity from thermal bands of ASTER sensor to delineate different lithounits of the granitoid family. We have compared emissivity and radiance image composites in terms of delineation of different granitoids. We have also used false colour composite (FCC) image derived using two emissivity bands and temperature (derived using emissivity normalisation method) bands to delineate different granitoids. We could differentiate different granitoids in the three-dimensional (3D) data space of ASTER-derived emissivity bands (second and third bands) and temperature bands. Based on the analysis of 3D scatter plot, we also proposed a ternary diagram of emissivity and temperature, which can be used to delineate different granitoids.

Spectroscopy of olivine basalts using FieldSpec and ASTER data: A case study from Wadi Natash volcanic field, south Eastern Desert, Egypt

This paper aims at revealing the spectral characteristics of the olivine basalts exposed at Wadi Natash area, Egypt, using FieldSpec spectroradiometer. It also evaluates band ratios and fusion techniques for mapping purposes using ASTER data. Several volcanic episodes occurred during Early- to Late-Cretaceous are recorded in the study area. Early-Cretaceous olivine basalts are highly carbonated. Late-Cretaceous eruptions took place throughout several volcanic cones aligned in NW direction. Based on FieldSpec measurements and petrographic data, two groups of olivine basalt namely ‘A’ and ‘B’ are recognized. Fresh olivine basalt (group A) is characterized by low flat spectral profile with overall low reflectance values (∼20%). Spectral profile of altered olivine basalt (group B) shows moderate reflectance values (∼37%) with four little absorption features around the 1.10, 1.40, 2.00 and 2.35 μm wavelength regions. These absorption features are attributed mainly to the presence of chlorite and carbonate alteration products as indicated by petrographic examination. ASTER false colour composite band ratio image (3/2:R, 8/1:G and 8/5:B) discriminates easily the fresh and altered basalts by deep blue and reddish blue colours respectively. Image fusion between previously mentioned FCC ratios image and high spatial resolution ASTER panchromatic image are carried out using brovey and HSV transformation methods. Visual and statistical assessment methods proved that HSV fusion image yields better image interpretability results compared to brovey image. It improves the spatial resolution of original FCC ratios image with acceptable spectral preservation. The present study proved the usefulness of FieldSpec spectral profiles and the processed ASTER data for discriminating different olivine basalt groups exposed at the study area.

Utilization of Space-Borne Imagery for Lithologic Mapping: A Case Study From Um Had Area, Central Eastern Desert, Egypt

Remote sensing data are used to discriminate between the different lithologies covering the Um Had area, Central Eastern Desert of Egypt. Image processing techniques applied to the Enhanced Thematic Mapper (ETM+) data are used for mapping and discriminating the different basement lithologies of Um Had area. Principal component analysis (PCA), minimum noise fraction (MNF) transform and band rationing techniques provide efficient data for lithological mapping. The study area is underlain by gneisses, ophiolitic melange assemblage (talc-serpentinite, metagabbro, metabasalt), granitic rocks, Dokhan volcanics, Hammamat sediments and felsites. The resulting gray-scale PC2, PC3 and PC4 images are best to clearly discriminate the Hammamat sediments, amphibolites and talc-serpentinites, respectively. The gray-scale MNF3 and MNF4 images easily discriminate the felsites and talc-serpentinites, respectively. The band ratio 5/7 and 4/5 images are able to delineate the talc-serpentinites and Hammamat sediments, respectively. Information collected from gray-scale and false color composite images led to generation of detailed lithologic map of Um Had area.

Assessment and Evaluation of Band Ratios, Brovey and HSV Techniques for Lithologic Discrimination and Mapping Using Landsat ETM<sup>+</sup> and SPOT-5 Data

This study aims to assess and to evaluate band ratios, brovey and HSV (Hue-Saturation-Value) techniques for discrimination and mapping the basement rock units exposed at Wadi Bulghah area, Saudi Arabia using multispectral Landsat ETM+ and SPOT-5 panchromatic data. FieldSpec instrument is utilized to collect the spectral data of diorite, marble, gossan and volcanics, the main rock units exposed at the study area. Spectral profile of diorite exhibits very distinguished absorption features around 2.20 μm and 2.35 μm wavelength regions. These absorption features lead to lowering the band ratio values within the band-7 wavelength region. Diorite intrusions appear to have grey and dark grey image signatures on 7/3 and 7/2 band ratio images respectively. On the false color composite ratio image (7/3:R; 7/2:G and 5/2:B), diorite, marble, gossan and volcanics have very dark brown, dark blue, white and yellowish brown image signatures respectively. Image fusion between previously mentioned FCC ratio image and high spatial resolution (5 meters) SPOT-5 panchromatic image is carried out by using brovey and HSV transformation methods. Visual and statistical assessment methods prove that HSV fused image yields best image interpretability results rather than brovey image. It improves the spatial resolution of the original FCC ratios image with acceptable spectral preservation.