False Colour Composite Research Articles

A New Approach in Individual Tree Counting of Nyatoh (<i>Palaquium</i> spp.) Using an Airborne Spectroradiometer

Problem statement: In Malaysia inadequate data are available to make decisions regarding the sustainable management of Nyatoh (Palaquium spp.). Factual data and estimation of Nyatoh in the lowland dipterocarp forest resources are still lacking or, if available, are not complete, reliable or up to date. The collection and compilation of information and updating of existing data in near real time is a priority. Nyatoh is one of the important and popular timber species for furniture, solid doors and planks. Approach: In order to determine Nyatoh's latest species count in the Federal Territory (FT)'s Permanent Reserved Forest, a study on the distribution of Nyatoh in Bukit Nanas Forest Reserve (FR), FT was conducted using an airborne hyperspectral remote sensing technique with an objective to identify, count and map the species of Nyatoh in Bukit Nanas FR, FT. A False Color Composite (FCC) airborne hyperspectral image of the study area was used with a Sobel 3×3 filter and Spectral Angle Mapper (SAM) to classify and separated the individual Nyatoh from other tree species within Bukit Nanas FR. Results: A thematic map of individual Nyatoh spatial distribution in Bukit Nanas FR was developed showing a total of 36 individual Nyatoh trees in a 2.7 h study plot. There were 34 trees confirmed available on the ground with a mapping accuracy of 94.4%. Conclusion: The AISA airborne spectroradiometer data is capable of mapping and counting individual tropical timber trees especially Palaquium spp. with an acceptable accuracy of more than 90%. However, in order to improve the mapping accuracy, it is recommended that a higher spatial resolution image data is necessary in addition to a higher precision field GPS usage. This approach may be well integrated in the GIS-based decision support system to better manage and conserve such depleting timber species in the FT’s state land and permanent reserved forests.

Identificação de Cerrado Rupestre por meio de imagens multitemporais do Landsat: proposta metodológica

O Cerrado Rupestre corresponde a uma formação savânica do bioma Cerrado, ocorre em relevos acidentados e em meio a afloramentos rochosos, apresenta elevada biodiversidade e várias espécies endêmicas e funciona como barreira para a expansão agrícola. No estado de Goiás, ocorrências expressivas dessa fitofisionomia são encontradas no Parque Nacional da Chapada dos Veadeiros (PNCV). O objetivo deste estudo foi desenvolver uma nova abordagem metodológica para discriminar Cerrado Rupestre do PNCV com base em imagens multitemporais do satélite Landsat. Sete cenas do referido satélite foram convertidas para reflectância de superfície terrestre com suporte do algoritmo de correção atmosférica denominado FLAASH (Fast Line-of-Sight Atmospheric Analysis of Spectral Hypercubes). Em seguida, os valores de reflectância de cada cena foram somados e as imagens resultantes foram processadas por meio da técnica de segmentação de imagens por crescimento de regiões. Os segmentos foram exportados para o formato shape e os polígonos correspondentes ao Cerrado Rupestre foram identificados por meio de análise visual na tela do computador da composição colorida falsa-cor das bandas 3, 4 e 5. Foram mapeados 24.451 hectares de Cerrado Rupestre, o que corresponde a 37% da área do parque. A exatidão global do mapeamento foi de 85%. Como continuação desta linha de pesquisa, recomenda-se a inclusão de um número maior de cenas, principalmente da estação chuvosa, a integração dos dados de sensoriamento remoto com modelos digitais de elevação e a análise sinergística entre os sensores ETM+ e TM do Landsat com calibração cruzada.

Applying Neural Network Classification to Obtain Mangrove Landscape Characteristics for Monitoring the Travel Environment Quality on the Beihai Coast of Guangxi, P. R. China

AbstractThe spectral characteristics of mangroves on the Beihai Coast of Guangxi, P. R. China are acquired on the basis of spectral data from field measurements. Following this, the 3‐layer reverse‐conversing neural networks (NN) classification technology is used to analyze the Landsat TM5 image obtained on January 8, 2003. It is detailed enough to facilitate the introduction of the algorithm principle and trains project of the neural network. Neural network algorithms have characteristics including large‐scale data handling and distributing information storage. This research firstly analyzes the necessity and complexity of this translation system, and then introduces the strong points of the neural network. Processing mangrove landscape characteristics by using neural network is an important innovation, with great theoretical and practical significance. This kind of neural network can greatly improve the classification accuracy. The spatial resolution of Landsat TM5 is high enough to facilitate the research, and the false color composite from 3‐, 4‐, and 5‐bands has a clear boundary and provides a significant quantity of information and effective images. On the basis of a field survey, the exported layers are defined as mangrove, vegetation, bare land, wetlands and shrimp pool. TM satellite images are applied to false color composites by using 3‐, 4‐, and 5‐bands, and then a supervised classification model is used to classify the image. The processing method of hyper‐spectrum remote sensing allows the spectral characteristics of the mangrove to be determined, and integrates the result with the NN classification for the false color composite by using 3‐, 4‐, and 5‐bands. The network model consists of three layers, i. e., the input layer, the hidden layer, and the output layer. The input layer number of classification is defined as 3, and the hidden layers are defined as 5 according to the function operation. The control threshold is 0.9. The training ratio is 0.2. The maximum permit error is 0.08. The classification precision reaches 86.86%. This is higher than the precision of maximal parallel classification (50.79%) and the spectrum angle classification (75.39%). The results include the uniformity ratio (1.7789), the assembly ratio (0.6854), the dominance ratio (–1.5850), and the fragmentation ratio (0.0325).

Three-channel false colour AFM images for improved interpretation of complex surfaces: A study of filamentous cyanobacteria

Imaging signals derived from the atomic force microscope (AFM) are typically presented as separate adjacent images with greyscale or pseudo-colour palettes. We propose that information-rich false-colour composites are a useful means of presenting three-channel AFM image data. This method can aid the interpretation of complex surfaces and facilitate the perception of information that is convoluted across data channels. We illustrate this approach with images of filamentous cyanobacteria imaged in air and under aqueous buffer, using both deflection-modulation (contact) mode and amplitude-modulation (tapping) mode. Topography-dependent contrast in the error and tertiary signals aids the interpretation of the topography signal by contributing additional data, resulting in a more detailed image, and by showing variations in the probe-surface interaction. Moreover, topography-independent contrast and topography-dependent contrast in the tertiary data image (phase or friction) can be distinguished more easily as a consequence of the three dimensional colour-space.

Dust source identification using MODIS: A comparison of techniques applied to the Lake Eyre Basin, Australia

The impact of mineral aerosol (dust) in the Earth's system depends on particle characteristics which are initially determined by the terrestrial sources from which the sediments are entrained. Remote sensing is an established method for the detection and mapping of dust events, and has recently been used to identify dust source locations with varying degrees of success. This paper compares and evaluates five principal methods, using MODIS Level 1B and MODIS Level 2 aerosol data, to: (a) differentiate dust (mineral aerosol) from non-dust, and (2) determine the extent to which they enable the source of the dust to be discerned. The five MODIS L1B methods used here are: (1) un-processed false colour composite (FCC), (2) brightness temperature difference, (3) Ackerman's (1997: J.Geophys. Res., 102, 17069–17080) procedure, (4) Miller's (2003:Geophys. Res. Lett. 30, 20, art.no.2071) dust enhancement algorithm and (5) Roskovensky and Liou's (2005: Geophys. Res. Lett. 32, L12809) dust differentiation algorithm; the aerosol product is MODIS Deep Blue (Hsu et al., 2004: IEEE Trans. Geosci. Rem. Sensing, 42, 557–569), which is optimised for use over bright surfaces (i.e. deserts). These are applied to four significant dust events from the Lake Eyre Basin, Australia. OMI AI was also examined for each event to provide an independent assessment of dust presence and plume location. All of the techniques were successful in detecting dust when compared to FCCs, but the most effective technique for source determination varied from event to event depending on factors such as cloud cover, dust plume mineralogy and surface reflectance. Significantly, to optimise dust detection using the MODIS L1B approaches, the recommended dust/non-dust thresholds had to be considerably adjusted on an event by event basis. MODIS L2 aerosol data retrievals were also found to vary in quality significantly between events; being affected in particular by cloud masking difficulties. In general, we find that OMI AI and MODIS AQUA L1B and L2 data are complementary; the former are ideal for initial dust detection, the latter can be used to both identify plumes and sources at high spatial resolution. Overall, approaches using brightness temperature difference (BT10–11) are the most consistently reliable technique for dust source identification in the Lake Eyre Basin. One reason for this is that this enclosed basin contains multiple dust sources with contrasting geochemical signatures. In this instance, BTD data are not affected significantly by perturbations in dust mineralogy. However, the other algorithms tested (including MODIS Deep Blue) were all influenced by ground surface reflectance or dust mineralogy; making it impossible to use one single MODIS L1B or L2 data type for all events (or even for a single multiple-plume event). There is, however, considerable potential to exploit this anomaly, and to use dust detection algorithms to obtain information about dust mineralogy.

Remote sensing detection of heavy oil through spectral enhancement techniques in the western slope zone of Songliao Basin, China

Landsat-7 enhanced thematic mapper plus (ETM+) imagery was used to identify anomalous areas caused by hydrocarbon leakage in Fula'erji in the western slope of Songliao Basin, China. Three image enhancement techniques, including principal component analysis (PCA), band ratioing, and false-color composition (FCC), were used. Based on the spectral characteristics of hydrocarbon-induced minerals and the eigenvectors of PCA, the best four principal components (PCs), 1345-PC3 (the third component of the PCA on bands 1, 3, 4, and 5), 1357-PC3, 3457-PC4, and 123457-PC4, were selected for FCC combined with band ratios of 3/1, 4/3, and 7/5. According to the tonal characteristics of the surface near wells and their visual expression, four FCC images were acquired for hydrocarbon-induced area delineation. The result indicates that anomalies are expressed as a faint tone blob and are mostly located in the Holocene sediments. An analysis of two cross sections traversing the identified anomalies suggests that they are closely related to the anomalous area interpreted from the four FCC images. Field data of magnetic susceptibility and delta carbonate are consistent with the distribution of the tonal anomalies and suggest a positive spatial association between the identified anomalous area and the hydrocarbon leakage environment.

Landslide mapping in the coastal area between the Strymonic Gulf and Kavala (Macedonia, Greece) with the aid of remote sensing and geographical information systems

The main aim of this study is to photointerpret land cover change along hill slopes in order to detect existing landslides with the aid of methodologies such as false colour composites (FCCs), principal component analysis (PCA) and the normalized difference vegetation index (NDVI). Then, by combining geological data (lithology, vegetation cover), and geomorphologic factors (slope, aspect, distance from the rivers), landslide susceptibility maps were produced. The region where the study took place was the coastal area between the Strymonic Gulf and southwest Kavala prefecture, which was selected because of its intense landslide activity. The identification of locations where landslides occurred was achieved with the use and processing of TERRA/ASTER satellite images, while the data, which were mainly collected from the digitization of contours from topographical maps at 1 : 50 000 scale, were used to construct the final landslide susceptibility maps. The resulting FCC images provided satisfactory information about the locations of landslide sites and the landslide susceptibility maps indicated areas that were more prone to produce such phenomena.

Semi‐automated methods for mapping wetlands using Landsat ETM+ and SRTM data

The overarching goal of this study was to develop a comprehensive methodology for mapping natural and human‐made wetlands using fine resolution Landsat enhanced thematic mapper plus (ETM+), space shuttle radar topographic mission digital elevation model (SRTM DEM) data and secondary data. First, automated methods were investigated in order to rapidly delineate wetlands; this involved using: (a) algorithms on SRTM DEM data, (b) thresholds of SRTM‐derived slopes, (c) thresholds of ETM+ spectral indices and wavebands and (d) automated classification techniques using ETM+ data. These algorithms and thresholds using SRTM DEM data either over‐estimated or under‐estimated stream densities (S d) and stream frequencies (S f), often generating spurious (non‐existent) streams and/or, at many times, providing glaring inconsistencies in the precise physical location of the streams. The best of the ETM+‐derived indices and wavebands either had low overall mapping accuracies and/or high levels of errors of omissions and/or errors of commissions. Second, given the failure of automated approaches, semi‐automated approaches were investigated; this involved the: (a) enhancement of images through ratios to highlight wetlands from non‐wetlands, (b) display of enhanced images in red, green, blue (RGB) false colour composites (FCCs) to highlight wetland boundaries, (c) digitizing the enhanced and displayed images to delineate wetlands from non‐wetlands and (d) classification of the delineated wetland areas into various wetland classes. The best FCC RGB displays of ETM+ bands for separating wetlands from other land units were: (a) ETM+4/ETM+7, ETM+4/ETM+3, ETM+4/ETM+2, (b) ETM+4, ETM+3, ETM+5 and (c) ETM+3, ETM+2, ETM+1. In addition, the SRTM slope threshold of less than 1% was very useful in delineating higher‐order wetland boundaries. The wetlands were delineated using the semi‐automated methods with an accuracy of 96% as determined using field‐plot data. The methodology was evaluated for the Ruhuna river basin in Sri Lanka, which has a diverse landscape ranging from sea shore to hilly areas, low to very steep slopes (0° to 50°), arid to semi‐arid zones and rain fed to irrigated lands. Twenty‐four per cent (145 733 ha) of the total basin area was wetlands as a result of a high proportion of human‐made irrigated areas, mainly under rice cropping. The wetland classes consisted of irrigated areas, lagoons, mangroves, natural vegetation, permanent marshes, salt pans, lagoons, seasonal wetlands and water bodies. The overall accuracies of wetland classes varied between 87% and 94% (K hat = 0.83 to 0.92) with errors of omission less than 13% and errors of commission less than 1%.

A semi-automatic method for burn scar delineation using a modified Chan–Vese model

We propose a novel semi-automatic method for burn scar delineation from Landsat imagery using a modified Chan–Vese model. Burn scars appear reddish-brown in band 742 false-colour composite of Landsat 7 images. This property is used in our algorithm to delineate burn scars. Firstly, we visually choose sample pixels from the burn scar. From these pixels, a discrimination function for burn scars is determined by the principal component analysis and interval estimation. Then we define a modified Chan–Vese functional. The minimizer of the functional corresponds to the boundary of the burn scar. In order to minimize this functional, the corresponding contour evolution equation is given. We use the discrimination function to locate an initial contour that is near the boundary of the burn scar. The evolving curve then efficiently converges to the desired boundary. A Landsat image over Russia is used to examine our algorithm. The result shows that the algorithm is effective.

Structural and remote sensing analysis of the Betsimisaraka Suture in northeastern Madagascar

The Betsimisaraka Suture (B.S.) of Madagascar is an important structural zone defining the collision between Eastern and Western Gondwana. It is represented by highly deformed high-grade metamorphic rocks with mineral assemblages typical of ophiolitic material, including chromitite and nickel bearing rocks consistent with a suture zone setting. Analysis of satellite imagery coupled with field investigations has helped to elucidate the structure and evolution of the B.S. Digital image processing of Landsat ETM+ data was integrated with Synthetic Aperture Radar (SAR) to reduce the effects of the dense vegetation cover. Enhanced false color composite (7-4-2 and 4-2-3), single Landsat bands and band ratio composites including 2/7-1/7-2/5, 5/3-5/1-7/3, 5/1-7/1-4/1 and 5/7-5/1-5/4 × 3/4 (in RGB) improve the lithologic contrast, reduce the effects of topography and enhance the structural lineaments. Ductile deformation deduced from structural features mapped on Landsat enhanced images indicates three generations of folding (F 1, F 2, and F 3) coupled with shearing: (1) F 1 folds with NE striking axial surfaces; (2) F 2 related with N–S striking axial surfaces, (3) and F 3 associated with ENE–WSW axial surfaces, indicating NNW and SSE contractional strain similar to the deformation in the southern B.S. Mapping these structures enables three types of shearing to be delineated: (1) NW–SE dextral shearing as seen in the Befandriana region; (2) NW–SE sinistral shearing defined by sigmoidal bodies in Mandritsara and Ankijanilava-Marotandrano regions, (3) and NE–SW striking dextral shears recorded in the Lake Alaotra region. Several faults, joints and fractures represent brittle deformation events. Lineaments analyzed within the B.S. are divisible into two groups of brittle structures: (1) N–S trending lineaments correlated with the Gondwanan collision events and (2) much younger NE and NW trending lineaments that are mainly found in the Antananarivo block. The latter may represent an active tectonic event in the central plateau that bounds the western part of the B.S.

Delineation and characterization of waterlogging and salt affected areas in a canal irrigated semiarid region of north west India

Indian Remote Sensing (IRS) Linear Imaging Self Scanning (LISS II) data are interpreted, followed by ground verification facilitated identification of waterlogged areas (ponded water), salt affected soils (salt efflorescence) and high water table zones (potential waterlogging zones) in the Indira Gandhi Nahar Pariyojona (IGNP) command area (India). The false colour composites (bands 4, 3, 2) for February 1996, November 1996 and June 1998 on 1:50 000 scale revealed occurrence and seasonal dynamics of permanent waterlogging in low-lying flats and depressions. The extent of waterlogging was higher in February 1996 due to less evaporation and more agricultural operation during the period. Salt accumulation was higher in November 1996 due to freshly precipitated seasonal salts. Seepage and accumulation of excess irrigation water through coarse sandy mass was primarily responsible for the development of waterlogging in the irrigated zone. The capillary rise of soluble salts with a rising water table and high evaporative demand caused secondary soil salinization. A ground truth study found areas with a high water table (<1.5 m) with patchy crop stands and a potentially sensitive zone with a fluctuating (1.5–6.0 m) water table with poor vegetative growth. The soil characteristics showed moderate to high soil salinity in the control section of soil profiles. These were characterized by medium to coarse texture, weak to moderately strong structure, weak consistency, low organic matter content and the presence of abundant CaCO3 nodules. The composition of saturated soil paste showed a preponderance of chlorides and sulphates of sodium, calcium and magnesium. The presence of fine texture and calcium carbonate layers at a depth below the surface caused the development of a perched water table indicating unsuitability for traditional irrigated agriculture. The quality of pond water was extremely poor and unfit for reuse. The ground water was saline in some areas but normally lies within the prescribed limit. The quality of drainage water was poor in saline depressions and unsuitable for reuse but moderate in other areas suggesting its safe reuse when mixed with good quality water. Suitable soil and water management practices were necessary for sustainable crop production in the command area.

Mapping and interpretation of Sinlap crater on Titan using Cassini VIMS and RADAR data

Only a few impact craters have been unambiguously detected on Titan by the Cassini‐Huygens mission. Among these, Sinlap is the only one that has been observed both by the RADAR and VIMS instruments. This paper describes observations at centimeter and infrared wavelengths which provide complementary information about the composition, topography, and surface roughness. Several units appear in VIMS false color composites of band ratios in the Sinlap area, suggesting compositional heterogeneities. A bright pixel possibly related to a central peak does not show significant spectral variations, indicating either that the impact site was vertically homogeneous, or that this area has been recovered by homogeneous deposits. Both VIMS ratio images and dielectric constant measurements suggest the presence of an area enriched in water ice around the main ejecta blanket. Since the Ku‐band SAR may see subsurface structures at the meter scale, the difference between infrared and SAR observations can be explained by the presence of a thin layer transparent to the radar. An analogy with terrestrial craters in Libya supports this interpretation. Finally, a tentative model describes the geological history of this area prior, during, and after the impact. It involves mainly the creation of ballistic ejecta and an expanding plume of vapor triggered by the impact, followed by the redeposition of icy spherules recondensed from this vapor plume blown downwind. Subsequent evolution is then driven by erosional processes and aeolian deposition.

Sediment concentration and bed form structures of Gulf of Cambay from remote sensing

The continental shelf on the west coast of India is the widest off Mumbai and leads to a strongly converging channel, the Gulf of Cambay (GoC). Tides in this Gulf are the largest on the Indian coast. The flow‐generated bed forms are significant features in the Gulf of Cambay region, and their presence depends on strong tidal or other currents, capable of moving the sand and also on the availability of sand. Digital data collected onboard Indian Remote sensing satellites IRS‐1C and IRS‐P4 OCM (Ocean Colour Monitor), covering the GoC region was digitally processed. False colour composites (FCC) of IRS‐1C were generated and used to map coastal, near‐shore geomorphic features and underwater flow‐generated bed form structures. Suspended sediment concentration and their dispersal patterns were studied by processing IRS‐P4 data. The impact of high tides on the suspended sediment concentration and sediment flow pattern was studied to understand the mechanism of sediment flow. Based on the suspended sediment concentration, flow structures, geomorphic features and hydrodynamics, it is concluded that fine‐grained sediments are transported to the inner Gulf, whereas, sandy sediments are transported south‐westwards and outwards of Gulf of Cambay. These sediments, perhaps participate in the formation of bed form structures.

Interpretation and processing of ASTER data for geological mapping and granitoids detection in the Saghro massif (eastern Anti-Atlas, Morocco)

Satellite remote sensing analysis is extensively used for geological mapping in arid regions. However, it is not considered readily applicable to the mapping of metamorphic and igneous terrains, where lithological contacts are less predictable. In this work, ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) data were used to clarify the geological framework of the Precambrian basement in the Saghro massif (eastern Anti-Atlas, Morocco). The Saghro basement is composed of low-grade metasedimentary sequences of the Saghro Group (Cryogenian), intruded by calc-alkaline plutons of late Cryogenian age. These rocks are unconformably covered by volcanic to volcaniclastic series of Ediacaran age that are broadly coeval with granitoid plutons. All of these units are cut by a complex network of faults associated with hydrothermal fluid flows, which developed during and shortly after the emplacement of the volcanic rocks. The geological mapping of the Precambrian units was challenging in particular for the Edicaran granitoid bodies, because they are characterized by very similar compositions and a widespread desert varnish coating. For this reason, a two-stage approach has been adopted. In the first step, false color composites, band ratios, and principal components analyses on visible and near infrared (VNIR) and shortwave infrared (SWIR) bands were chosen and interpreted on the basis of the field and petrographic knowledge of the lithologies in order to detect major lithological contacts and mineralized faults. In the second step, a major effort was dedicated to the detection of granitoid plutons using both thermal infrared (TIR) and VNIR/SWIR data. The ASTER TIR bands were used to evaluate Reststrahlen and Christiansen effects in the granitoid rocks spectra, whereas VNIR/SWIR false color composite and ratio images were chosen directly on the basis of the granitoid spectra (derived from both spectrophotometric analyses of samples and selected sites in the ASTER image). Finally, spectral angle mapper (SAM) and supervised maximum-likelihood classifications (MLL) were carried out on VNIR/SWIR data, mainly to evaluate their potential for discriminating granitoid rocks. The results have further demonstrated the value of ASTER data for geological mapping of basement units, particularly if the processing has been based on a detailed knowledge of the rock mineral assemblages. In addition, the analytical comparison of ASTER TIR and VNIR/SWIR data has demonstrated that the latter are very effective in the distinction of granitoids with very similar silica content, because they can be recognized by secondary effects related to their hydrothermal and surface alterations (K-feldspar kaolinitization, plagioclase saussiritization, substitution of mafic minerals with oxides, inhomogeneous desert varnish coating, and clay/oxide proportions).

Assessment of land use changes using remote sensing and GIS and their implications on climatic variability for Balachaur watershed in Punjab, India

Abstract Decadal changes in land use/land cover for Balachaur watershed in Nawanshahar district, Punjab, India were studied using black and white aerial photographs for March 1984 on approximately 1:20,000 scale and multidate geocoded false colour composites (FCC) of IRS-1D LISS-III on 1:50,000 scale for March 2002, September 2002, and May 2003 and interpreted visually to prepare land use/land cover maps for the year 1984 and 2003. The results revealed that the area under crop land, moderately dense forest, degraded forest, degraded land in hills and piedmont plains, barren land along choes (seasonal streams) has decreased; whereas, the area under settlements, dense forest, plantations, industrial use, ponds, choes and brick kilns has increased over a span of 20 years. By virtue of afforestation and forest conservation, the density of vegetation in Siwalik hills and piedmont areas has increased. The area under moderately dense forest (1956.7 ha) and degraded forest (755.5 ha) got upgraded to dense forest while 755.5 ha of degraded forest changed to moderately dense forest. The impact of land use/land cover alterations on climatic variability at micro-level revealed that the linear trends computed for the 5-yearly moving average of maximum temperature showed an increasing trend from 1984 to 2003, whereas the minimum temperature, rainfall, and potential evapotranspiration showed a decreasing trend. Inspite of increasing forest cover in the study area, these trends in different meteorological parameters did not corroborate the findings of some earlier reports. Thus land use/ land cover changes over time may not be the only factor which causes variation in meteorological parameters. It implies that there might also be other factors such as CO2 concentration and its effect on green house gases, atmospheric pollution and spectral distribution of the incoming solar radiation, which affect climatic variability in a region. Keywords: Land use change; Climatic variability; Remote sensing; Potential evapotranspiration

Detection of hydrocarbon bearing sand through remote sensing techniques in the western slope zone of Songliao basin, China

To detect oil‐bearing sand in the western slope zone of Songliao Basin, China, a Landsat‐7 Enhanced Thematic Mapper Plus (ETM+) image was used to identify anomalous areas caused by hydrocarbon leakage. Enhancement of the image involved three techniques including Principal Component Analysis (PCA), band ratioing and False Colour Composition (FCC). In this paper, experimental work gives a detailed PCA description of different band combinations. The best four principal components (PCs)—1345‐PC3 (the third PC image of the PCA on band 1, 3, 4, 5), 1357‐PC3, 2357‐PC3 and 3457‐ PC4—were selected for FCC combined with band ratio layers. Based on the tonal characteristics of the existing bores and the basin boundary, differentiation of target areas in the four FCC images was achieved. Results indicated that anomalies are expressed as a halo in fuscous tone and located in the basin margin with an area of 70∼100 km2. Examination of the Ce/La ratio showed that the tonal anomalies are evidently associated with a reducing environment.

Mapping Proterozoic unconformity-related uranium deposits in the Rockhole area, Northern Territory, Australia using landsat ETM+

The Rockhole area, Northern Territory, Australia, hosts a number of Proterozoic unconformity-related uranium deposits. The geology of the area features within Paleoproterozoic rocks of the Pine Creek Orogen, near the unconformity with overlying platform cover sandstone of the Paleo- to Mesoproterozoic McArthur Basin. Landsat Enhanced Thematic Mapper plus (ETM+) data was used in the Rockhole area to assist in mapping geological structures and lithology, and to identify anomalous concentrations of ferrous minerals, the product of alteration, which can be indicators of buried uranium mineralization. Several image-processing procedures were applied to the ETM+ data to identify, isolate and enhance mineralogical information as simple and complex false color composites. ETM+ 754 shown as red green and blue respectively was the best simple image. Overall, complex images based on Principal Component Analysis proved to be the most useful products. Sandstone, shale and siltstone, the target lithologies, Koolpin Formation, the target stratigraphic unit, and bleaching pattern due to the removal of iron(II) compounds, the target alteration pattern, were confidently mapped to provide information required by the mineral emplacement model, which ultimately identified areas of likely uranium mineralization. Thus the contrasting behavior of the two principle oxidation states of uranium and iron can be utilized to map/delineate bleached alteration zones associated with economic concentrations of uranium using multispectral sensors like Landsat or better hyperspectral sensors.

Recent glacier retreat in the Caucasus Mountains, Russia, and associated increase in supraglacial debris cover and supra-/proglacial lake development

AbstractThis paper reports changes in supraglacial debris cover and supra-/proglacial lake development associated with recent glacier retreat (1985–2000) in the central Caucasus Mountains, Russia. Satellite imagery (Landsat TM and ETM+) was used to map the surface area and supraglacial debris cover on six neighbouring glaciers in the Adylsu valley through a process of manual digitizing on a false-colour composite of bands 5, 4, 3 (red, green, blue). The distribution and surface area of supraglacial and proglacial lakes was digitized for a larger area, which extended to the whole Landsat scene. We also compare our satellite interpretations to field observations in the Adylsu valley. Supraglacial debris cover ranges from &lt;5% to &gt;25% on individual glaciers, but glacier retreat between 1985 and 2000 resulted in a 3–6% increase in the proportion of each glacier covered by debris. The only exception to this trend was a very small glacier where debris cover did not change significantly and remote mapping proved more difficult. The increase in debris cover is characterized by a progressive up-glacier migration, which we suggest is being driven by focused ablation (and therefore glacier thinning) at the up-glacier limit of the debris cover, resulting in the progressive exposure of englacial debris. Glacier retreat has also been accompanied by an increase in the number of proglacial and supraglacial lakes in our study area, from 16 in 1985 to 24 in 2000, representing a 57% increase in their cumulative surface area. These lakes appear to be impounded by relatively recently lateral and terminal moraines and by debris deposits on the surface of the glacier. The changes in glacier surface characteristics reported here are likely to exert a profound influence on glacier mass balance and their future response to climate change. They may also increase the likelihood of glacier-related hazards (lake outbursts, debris slides), and future monitoring is recommended.

The application of advanced space-borne thermal emission and reflection (ASTER) radiometer data in the detection of alteration in the Chadormalu paleocrater, Bafq region, Central Iran

Ore deposits are often produced by fluid flow processes that alter the mineralogy and chemistry of the country rock. One of the main objectives in developing a multi-spectral and hyperspectral sensor is to detect the optical characteristics of the Earth’s surface using hundreds of spectral bands. All previous studies show that remote sensing can recognize alteration to different degrees, using different spatial and spectral resolution sensors. The ASTER sensor measures reflected radiation in VNIR, SWIR and TIR electromagnetic energies. It is cheap and easily available. The alteration minerals in the Precambrian Chadormalu area (Chadormalu paleocrater and the related iron oxide deposit) have been investigated in the field and have been successfully detected by applying IARR (Internal Average Relative Reflectance), FCC (False Color Composite), Decorrelation-stretch, MNF (Minimum Noise Fraction Transform), correlated filter and MEM (Mathematical Evaluation Method) techniques on ASTER imageries. Sodic, potassic, and silicic–phyllic alteration patterns can be distinguished. This study shows that the capability and accuracy of the MEM method is better than 2 × 2 correlated filter techniques. Results indicate that pervasive hydrothermal ore-forming processes were important in the study area. Judging from the assemblage of alteration minerals, the Chadormalu iron deposit is an end-member of the Kiruna type – Iron oxide (Cu–Au) ore deposit continuum.

Remote sensing study of granulitic terrain in parts of Gujarat and Rajasthan

The geology of northwestern part of Indian peninsula is considered to be important due to complete preservation of rocks from Archaean to Upper Proterozoic. Further, these rocks have served as ideal host of varieties of economic minerals. The present work is an attempt to study the structurally deformed granulitic terrain in parts of Gujarat and Rajasthan in light of remote sensing. The study area falls under Sirohi, Banas Kantha and Sabar Kantha districts of Rajasthan and Gujarat. Remote sensing technique is utilized for the understanding of structural geology and deciphering the shear pattern. The methods adopted in this study include generation of False Color Composite (FCC) of satellite data, interpretation of lineaments from FCC and study the drainage pattern, structural basin delineation, profiling, and field mapping. It is observed that the area has undergone extensive deformation. There are two major sets of lineaments interpreted in the granulitic terrain such as WNW-ESE and NE-SW directions. Majority of the WNW-ESE lineaments are brittle in nature and N-S, NE-SW trending lineaments are ductile in nature. Overall the study area bifurcated into seven structural basins comprises of basic granulites, calc granulites and pelitic granulites.