An evaluation of SPOT-simulation imagery for land-use mapping and ecological investigations in upland areas of Northern Ireland

Abstract

In Northern Ireland peat and marginal land dominate uplands, form significant cover in lowlands and, together with the small-scale intricate nature of field systems, result in a landscape unlike many other parts of the United Kingdom.

Four cover types are considered in the analysis of SPOT-simulated imagery ­peat, marginal land, forests and improved grassland. Results suggest potential use of SPOT in delimitation and differentiation of peat areas for commercial and conservation purposes; monitoring of forest environments; assessing suitable areas for hill-land improvement; and a general land utilization survey.     

Library System Packages-Revisited

Abstract

This is the second part of a three-part article. Part I, which appeared in the February 1983 issue of EDPACS, dealt with approaches to computer contracting, applicable law, and vendor contracts. Part III, scheduled to appear in the April 1983 issue, will cover project control concepts and contract negotiation.     

Observations of the snowcover on sea ice in the Gulf of Bothnia

Abstract

During March 1988, detailed measurements of the physical properties and depth distributions of the snow cover on the sea ice in the Gulf of Bothnia were made as part of BEPERS-88 (Bothnian Experiment in Preparation for ERS-1). The observations included profiles of the density, crystal structure. salinity, temperature, and brine volume (at 1-2 cm depth intervals), and 1084 snow depth measurements. These data are presented along with discussions of the implications of the measured properties for the interpretation of SAR imagery, and the use of laser profilometry for remotely estimating ice surface roughnesses.     

AGGREGATION,EMERGENCE AND IMMERGENCE IN HIERARCHICALLY ORGANIZED SYSTEMS

Abstract

The aim of this work is to show that couplings between fast micro-dynamics and slow macro-dynamics can make emerge global properties. Emergence corresponds to a bottom-up coupling, that is to the effect exerted by a micro-level at a macro-level. Immergence corresponds to the inverse process, that is to an up-down coupling. As an example, we present a prey-predator model with different time scales in a heterogeneous environment. A fast time scale is associated to the migration process on spatial patches and a slow time scale is associated to growth and interactions between the populations. Preys go on spatial patches where resources are located and where predators can attack them. The efficiency of predators is patch-dependent. Perturbation theory is used in order to aggregate the initial system of ordinary differential equations for patch sub-populations into a macro-system of two differential equations governing total populations. First, we study a case of density-independent migrations, for which no emergence occurs. Then, we study some examples of density-dependent migrations. In this case, emerging properties appear at the population level.     

Monitoring coastal erosion at the Black Sea coasts in Turkey using satellite data: A case study at the Lake Terkos,north-west Istanbul

There is justifiable cause for concern over the adequacy of our water supplies. To control and protect aquatic ecosystems and drinking water supplies, continuous monitoring is essential. An example related to the careless attitudes towards the Lake Terkos, Istanbul, which create the danger of waterlessness for citizens was given in this study. The width of the natural land barrier between the Black Sea and the Lake Terkos has decreased over the years due to illegal sand excavation along the coastline of the sea very close to the northern part of the lake. As a result of this process the offshore bar formation along the coastline has been destroyed and even removed at different parts, which caused morphological changes of the coastline along some parts of the northern coasts of the sea. In this paper, the coastal erosion during a 14-year period was monitored by using multitemporal satellite sensor data and some suggestions for precautions were made.     

Non-stationary and unequally spaced NDVI time series analyses by the LSWAVE software

ABSTRACT

Change detection within non-stationary and unequally spaced remote sensing time series has become a key methodology for a broad range of environmental applications. A new method of analysing vegetation variation over lands is proposed. Four regions in northern Tunisia with various characteristics are selected, and a non-stationary and unequally spaced Normalized Difference Vegetation Index (NDVI) time series is obtained for each region since 2000. The Landsat 7 remote sensing satellite imagery with insignificant cloud-shadow coverage is used to calculate the NDVI after atmospheric correction. The Least-Squares Wavelet (LSWAVE) software is implemented to rigorously analyse each NDVI time series and study the relationship between the vegetation of olive trees and temperature/precipitation in one of the regions. To investigate possible effects of temperature on the green cover caused by increasing water salinity, the coherency between the NDVI and sea surface temperature time series is also shown in the region of Lake Ichkeul in Tunisia.     

A multi-scale approach to mapping effective Leaf Area Index in Boreal Picea mariana stands using high spatial resolution CASI imagery

This study evaluates the performance of a simple geometric-optics reflectance model, used in combination with multi-spectral clustering, to map spatial patterns of effective Leaf Area Index ( L e ) within Boreal Picea mariana stands. Two metre resolution Compact Airborne Spectrographic Imager (CASI) images, acquired during the winter to minimize variability in understory reflectance, are used to map L e over BOREAS northern and southern Old Black Spruce tower flux sites. A combined multi-spectral clustering and ray-tracing approach is used to map open areas in each site at 2 m scale. A modified version of the Forest Light Interaction Model (FLIM) is then applied over canopy areas using 30 m scale red and near-infrared reflectance values derived from CASI images. Comparison of the combined FLIM and clustering approach (FLIMCLUS) with surface L e measurements in areas with overstory cover indicate a R 2 of 0.67 for the SSA-OBS site and 0.16 for the NSA-OBS site. The poor NSAOBS performance may be due to the low observed range of L e along the transect selected since additional measurements in a sparse canopy area closely match FLIM estimates. The relative standard error at both sites is under 10% and is close to the 5% precision error in surface L e estimates. Comparison of FLIMCLUS with FLIM and the simple ratio indicate substantial differences over open areas where the latter methods map-zero L e values. Further validation over other study sites, including surface data mapping edges between canopy and open areas, is proposed. The FLIM-CLUS L e maps may be useful for testing scale dependent assumptions within remote sensing algorithms and ecosystem flux models applied to the study sites and similar Picea mariana stands.     

Ocean sand ridge signatures in the Bohai Sea observed by satellite ocean color and synthetic aperture radar measurements

Satellite measurements from Synthetic Aperture Radar (SAR) and the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard the Aqua platform are used to study the ocean sand ridges in the eastern Bohai Sea in China. Even though the imaging mechanisms for SAR and MODIS-Aqua remote sensing are different, the sand ridges are shown to have exactly the same patterns in images from both sensors. Therefore, the location, extension and coverage of the ocean sand ridges can be detected and cross-examined by both SAR and MODIS-Aqua observations. Satellite images show quite different sand ridge distribution pattern from the published bathymetry map (based on in situ data) that shows six sand ridges in the area. 10 finger-shaped sand ridges are identified from satellite observations. The tidal-current/sand-ridge interaction driven physical and optical changes are assessed and evaluated. The existence of sand ridges causes enhanced water diffuse attenuation coefficient K_d(490) and elevated normalized water-leaving radiance at the red and near-infrared (NIR) wavelengths. The sea surface over the sand ridges experiences significant seasonal variability of water turbidity and shows remarkable differences from nearby ocean regions. During winter, K_d(490) values are about 2-3 m^− 1 over the ridges, while the maximum K_d(490) in the neighboring oceans is approximately 1.5 m^− 1. In summer, the enhancement of the sea surface turbidity is less significant than that which occurs in winter.     

Linear mixture modelling applied to AVHRR data for crop area estimation

Abstract

A technique for estimating crop coverage using linear mixture modelling of multi-temporal Advanced Very High Resolution Radiometer (AVHRR) data is presented for a study area in northern Greece. This paper identifies some of the problems associated with using satellite sensor data with coarse spatial resolution for crop area estimation. Using satellite sensor imagery with a high spatial resolution to extrapolate ground measurements to AVHRR scales, the paper shows how the mixture model can be applied to AVHRR data in a mixed agricultural system. Crop areas are estimated to an average accuracy of 89 percent on regional scale using this technique. The results show that this linear mixture modelling has potential for operational crop area monitoring on a regional basis.     

Remote sensing and Pleistocene tectonics of Southern Indian peninsula

The southern part of the Indian Peninsula has long been regarded as a stable area free from Pleistocene tectonics as it represents the Precambrian shield region. But the frequent earth tremors even up to a magnitude of 6-5 ( Richter scale) which occurred in Tamil Nadu have started encouraging the geologists to think that it could possibly be a seismic prone zone. In addition, images acquired by the polar orbiting satellites offered valuable information on the fracture systems and fluvial anomalies suggesting possible Pleistocene tectonism in South India. Hence, a study has been undertaken to evaluate the signatures of Pleistocene tectonism in South India using 1RS-1A, LISS-I FCC imagery ( Indian Remote Sensing Satellite 1A, Linear Imaging Self Scanning 1, False Colour Composite) involving band 2, 3 and 4 under blue, green and red bands respectively

The study has brought out a series of E-W trending cymatogenic arches and N-S trending extension, NE-SW trending sinistral, NW-SE trending dextral and E-W trending release fractures with characteristic signatures supporting Pleistocene tectonism in Tamil Nadu and Kerala

On the basis of such morphotectonic features, a Pleistocene tectonic model has been presented with a N-S trending greatest principal stress and an E-W oriented least principal stress related to the movement of the Indian plate towards the Tibetan plate.

Based on the model developed for Tamil Nadu and Kerala, a series of E-W trending cymatogenic arches and deeps have been proposed for Cochin-Rameswaram in the south to the Himalayas in the north. Further studies for seismotectonics, geothermal resources and hydrocarbon search have also been suggested along such arches and deeps.     

Deriving terrain and textural information from stereo RADARSAT data for mountainous land cover mapping

A new procedure is proposed for land cover classification in a mountainous area using stereo RADARSAT-1 data. The method integrates a few types of information that can be extracted from the same stereo RADARSAT images: (1) the Digital Elevation Model (DEM) generated from the stereo RADARSAT images; (2) terrain information (elevation, slope and aspect) extracted from the derived DEM; and (3) textural information derived from the same RADARSAT images. An Artificial Neural Network (ANN) classifier is applied for the land cover classification. Performance of the proposed method is evaluated using a mountainous study area in Southern Argentina, where there is a lack of up-to-date information for environmental monitoring. The results show that the integration of textural and terrain information can greatly improve the accuracy of the classification using the ANN classifier. It demonstrates that stereo RADARSAT images provide valuable data sources for land cover mapping, especially in mountainous areas where cloud cover is a problem for optical data collection and topographical data are not always available.     

AVHRR visible-IR detection of diurnal warming events in the western Mediterranean Sea

Abstract

Diurnal warming of the sea surface temperature (SST) is often observed in the spring and summer Advanced Very High Resolution Radiometer (AVHRR) imagery of the Mediterranean Sea. It masks SST features of oceano-graphic interest. Diurnally warmed regions, where low wind conditions prevail, exhibit smooth surface and thus are characterized by low reflected solar radiation except for specular reflection of the visible solar radiation. Utilization of this correlation through clustering of diurnally warmed areas in an infrared-visible histogram permits discrimination from areas where the SST is representative of the underlying bulk temperature.     

A simple geometrical model for analysing the spectral response of a citrus canopy using satellite images †

Abstract

A simple geometrical model has been proposed for a citrus canopy. We assume the citrus orchard to be a lattice structure, with the trees positioned at its points and where the composite-scene reflectance is the sum of the reflectance of its individual components as weighted by their respective surfaces within a unit area. The model has been used to analyse the citrus spectral response obtained from Landsat-5 TM images for winter and summer, where the status of the orchard is different. The correlations between spectral and geometrical data show the influence of per cent crop cover, shadows and background in the composite scene reflectance. We conclude that the summer images could be more useful than the winter ones for parcel classification according to per cent crop cover.     

The measurement of suspended particulate concentrations from remotely-sensed data

Abstract

Knowledge of the distribution of SPM is recognised to be of increasing importance in relation to the prediction of the fate of pollutants in the shelf seas. Persistent patterns in SPM and a marked annual cycle are observed in the shelf seas around the United Kingdom. Although concentrations of surface suspended particulate material can be related to the imagery, little insight into the processes causing the variations can be gained without knowledge of the depth variability. Assessment of the spatial variation was facilitated by regular conductivity, temperature, depth (CTD) and transmissometer surveys from March to October 1987, in an area of the Irish Sea where there were marked gradients in the sea surface reflectance. This showed that although surface concentrations showed similar trends to sea surface reflectance, vertical gradients in suspended particulate material were associated with the seasonal pycnocline. The time dependance of beam attenuation and its control by tidal currents were assessed by the analysis of a six month record of transmissometer and current meter data from a mixed-water site. Beam attenuation was found to be significantly related to the springs-neaps cycle, advective processes and to the time of year. The study shows that remotely-sensed sea surface reflectance data have a significant part to play in the measurement of suspended particulate material if they are coupled with a carefully planned survey of in situ optical and oceanographic measurements.     

遥感图像中尺度海洋锋及涡旋提取方法研究进展

目的 中尺度海洋锋及涡旋均是重要的中尺度海洋环境特征。中尺度海洋锋及涡旋的提取及其时空分布、变化的研究对海洋生态系统的研究、渔业资源评估、渔情预报及军事等都有重要意义。遥感技术能在同一时间获取大面积海洋要素观测数据,遥感数据具有优良的连续性、同步性,因此遥感数据被广泛应用于中尺度海洋锋及涡旋提取的研究中。方法 对基于遥感数据进行中尺度海洋锋提取的梯度法、Canny算法、小波分析法和基于引力模型的方法,以及涡旋的提取的Okubo-Weiss法（OW法）、Winding-Angle法（WA法）、基于海面高度的无阈值等值线法和Hybird Detection（HD法）进行总结和分析,并提出对中尺度海洋锋面及涡旋提取方法的见解及新思路。结果 利用2014年2月南海北部海表温度（SST）数据,分别采用梯度法中的Gradient法、Sobel算法以及Canny算法对南海北部温度锋进行提取并得到该区域温度锋分布图。结果 明在多种锋面提取方法中,Canny算法具有较高的效率且其提取结果的连续性和精度更好。中尺度涡的提取方法中,WA法的提取结果具有更好的准确性。早期的中尺度涡提取方法忽略了多中心结构涡旋存在的情况,而后来的HD法能较好地识别多中心结构涡旋。结论 阈值选取是中尺度海洋锋及涡旋提取的难点和提取结果好坏的关键。然而海洋要素图像弱边缘的特点使得传统边缘检测方法不一定适用于中尺度锋提取。文章通过对不同锋面及涡旋提取方法的总结与分析,为海洋锋面及涡旋提取的研究提供了参考依据。     

Comparison of unified full-wave solutions for normal incidence microwave backscatter from sea with physical optics and hybrid solutions

Abstract

The unified full-wave solution for electromagnetic wave scatter from a rough surface is expressed as an integral similar in form to physical optics solutions. However it correctly predicts return for small and intermediate roughness scales where the physical optics approach fails. This full-wave solution is used here to evaluate microwave sea surface backscatter at normal incidence for both the like-and cross-polarized linear components. Surface heights and slopes are assumed to be Gaussian, the sea is characterized by its surface height spectral density function and both perfectly and finitely conducting surfaces are considered. Results from this complete full-wave evaluation are compared with approximations, involving single-scale (specular point) and two-scale models. For both of these models, however, it is necessary to assume a spectral wavenumber, ν_d, where spectral splitting between the large and the small scales of the rough surface occurs. The full-wave solution is used as a guide in the selection of ν_d and to study the accuracy and sensitivity of the different approximations to ν_d. It is also shown that results for cross-polarized backscatter based on the physical optics or two-scale models are totally inadequate.     

Review of: “ Télédétection spatiale: Université d' été européenne Toulouse 1990”. By MICHEL VAUZELLE (Cépadues-Éditions. Toulouse. 1992) [Pp. 309.] Price FF300.

In this paper, a simple model is proposed for measuring the vegetation cover over soil surfaces from radar signals acquired in semi-arid regions. In such regions, vegetation is characterized by the presence of clumps which partially cover the soil surface. The proposed model describes the relationship between the percentage of covered surface and the measured radar signal. Model simulations over Tunisian test areas, where ground parameters are controlled, are performed and compared with actual ERS2 radar measurements. A very good agreement is found. The model is then used to derive a map of the vegetation cover density for the whole studied site (in Tunisia). The approach used here is based upon supervised classification with classes defined by inverting the model and taking into account ERS calibration error. Each of the four classes thus defined exhibits a good classification rate, greater than 85%. Finally, two important applications for natural resources management are presented: vegetation monitoring and soil moisture monitoring.     

Quantifying urban land use and impact on soils in Egypt using diurnal satellite imagery of the Earth surface

Conversion of agricultural land to urban use represents a potential loss of agricultural productivity, especially in areas where arable land is in short supply. Using derived products from both daytime (Landsat sensor data) and night-time imaging systems (U.S. Air Force Defense Meteorological Satellite Program's Operational Linescan System (DMSP/OLS)) we examined the impacts of urbanization on soils in Egypt; a country with very limited agricultural land. We concluded that urban land cover types to occupy 3.7% of the total area of Egypt and that over 30% of the soils most suitable for agriculture are under urban land cover. Analysis of multiyear historical DMSP/OLS data sets (digitized from paper images) proved unreliable for long-term urban growth estimates.     

Spatio-temporal distribution of burned areas by ecoregions in Mexico and Central America

Fire activity in Mexico and Central America, and its associated emissions, has impacts across multiple scales. On the local-to-regional scale, fire activity impacts land use, productivity, and biodiversity. On the regional-to-global scale, fire activity impacts hydrological, biogeochemical, and atmospheric processes. A consistent, reliable, large-scale characterization of the spatial and temporal distribution of fire burned area is required to assess its environmental impacts and to support natural resources’ management. The spatial and temporal distributions of fire burned areas in ecoregions of Mexico and Central America are evaluated in this study for the period 2001–2014, using the satellite Moderate Resolution Imaging Spectroradiometer (MODIS) MCD45 Burned Area data set. The methodology combines the 500 m burned area product with a MODIS land cover product and a map of North American land cover to calculate the spatiotemporal variability of fire activity as a function of land-use type.

The total burned area over Mexico and Central America over the period 2001–2014 was found to be 614,243.5 km², but with significant interannual variability over the 14 years included in the study. Indeed, the minimum burned area over the period was 9892.25 km² in 2014 and the maximum was 37,669.50 km² in 2011, a fourfold increase. Burned areas were found to be concentrated in northern Mexico and on the Pacific coast, mainly from October to June. Agricultural burned areas accounted for 37% and 43% of total detected burns in Mexico and Central America, respectively. The largest extent of burned surface occurs in May for most land-cover types. The maximum density of burned areas occurred in the tropical dry forests ecoregion during the dry season. Both in Mexico and Central America, burned area anomalies have significant anti-correlation with precipitation anomalies.     

Drainage network analysis of LANDSAT images of the Olympus-Pieria mountain area,northern Greece

This report is an account of findings derived from a visual examination of 1:250000 paper print enlargements of LANDSAT black-and-white images (from bands 5 and 7), paper print enlargements of LANDSAT false-colour composites (bands 4, 5 and 7) and maps of a representative part of the Mediterranean climate area of the Olympus-Pieria mountains and the surrounding area in northern Greece.

The main finding derived from this image and map interpretation was that the l:250000-scale enlarged prints are far more suitable for quantitative analysis of drainage networks than the topographical maps of an equivalent scale. For the study area as a whole, the LANDSAT images showed channels (streams) up to higher order than the same scale topographical maps. Also, the number of streams and the total stream lengths of each order, which appeared on LANDSAT images, were significantly more than on topographical maps, illustrating the greater amount of detail which can be extracted from images.

Furthermore, it was concluded that near-infrared (band 7) LANDSAT images offer the best prospects between the four MSS spectral bands of LANDSAT-3 for the detection of drainage lines in vegetated and fluvially dissected areas but they are less effective in the detection of small drainage lines, particularly where they are turbid or choked with vegetation; however they are still superior to the red (band 5) image. This limitation was partly overcome by using false-colour composites since they were more suitable for the recognition of the vegetated streams.