Panchromatic Aerial Photographs Research Articles

Computerized classification of Mediterranean vegetation using panchromatic aerial photographs

Abstract.Historical aerial photographs are an important source for data on medium‐ to long‐term (10 ‐ 50 yr) vegetation changes. Older photographs are panchromatic, and manual interpretation has traditionally been used to derive vegetation data from such photographs. We present a method for computerized analysis of panchromatic aerial photographs, which enables one to create high resolution, accurate vegetation maps. Our approach is exemplified using two aerial photographs (from 1964 and 1992) of a test area on Mt. Meron, Israel. Spatial resolution (pixel size) of the geo‐rectified photos was 0.30 m and spatial accuracy (RMS error) ca. 1 m. An illumination adjustment prior to classification was found to be essential in reducing misclassification error rates. Two classification approaches were employed: a standard maximum‐likelihood supervised classifier, and a modification of a supervised classification, which takes into account spectral properties of individual pixels as well as their neighbourhood characteristics. Accuracy of the maximum likelihood classification was 81 % in the 1992 image and 54 % in the 1964 image. The neighbour classifier increased accuracy to 89 % and 82 % respectively. The overall results suggest that computerized analysis of sequences of panchromatic aerial photographs may serve as a valuable tool for the quantification of medium‐term vegetation changes.

Topographic mapping of the volcano Nevado Ojos del Salado using optical and microwave image data

The area of interest is located at the border between Chile and Argentina at 27°10’ S. latitude and 68°30’ W. longitude in the High Cordillera of the Andes and includes the second‐highest mountain of America, the Nevado Ojos del Salado. Although the official Chilean altitude is given as 6,880 m, other figures can be found in the literature and various other maps. Situated in a picturesque volcanic terrain rising above the Puna de Atacama, Nevado Ojos del Salado is not only interesting from a geomorphological point of view, it is, e.g., the world's highest volcano, but also has recently become a much‐favored destination of the mountaineering world. Unfortunately, this area is not covered by reliable and publicly available maps at scales larger than 1:250,000. Therefore, this paper describes the methods employed in and results obtained from topographic mapping of this remote area using spaceborne as well as airborne remotely sensed data. Exploiting Space Shuttle Earth‐viewing photographs, ERS‐1 Synthetic Aperture Radar images, and aerial photographs, it was intended to derive orthophotos, digital elevation models, topographic/geomorphological base maps, including various derivatives, such as anaglyphs, stereograms, and axonometric views, respectively, at a minimum of costs. In order to get a general overview, i.e. to generate a base map of the area, stereoscopic hand‐held photographs from NASA's SSEOP database were used. Parallax‐free stereo vision was achieved by means of an analytical plotter. Ground control points were taken from the existing Chilean maps at scales 1:250,000 and 1:500,000 in order to georeference the image content. A digital orthophoto and a topographic base map at 1:400,000 are presented. Furthermore, two overlapping same‐side ERS‐1 SAR images from adjacent descending orbits were acquired and provided in digital format by the European Space Agency. In a first step, the image data was radiometrically enhanced, and proper radar stereograms were generated for image interpretation purposes. This is followed by a brief discussion of recently developed mapping methods for radar images. In order to facilitate large‐scale mapping a strip of panchromatic aerial photographs at 1:30,000 scale, provided by the Instituto Geografico Militar de Chile, was photogrammetrically oriented using ground control points measured in one of the Shuttle stereopairs at 1:840,000 scale. As a result, a topographic map at 1:15,000 scale and a high‐resolution digital elevation model of the central part of the Nevado Ojos del Salado were generated. The photographs, given as analog paper prints, were scanned and thereafter digitally rectified and mosaicked to form an orthophoto of the volcano Ojos del Salado. A stereomate of this orthophoto was produced as well. The scope of this work also includes various combined image‐line maps. The presented cartographic products, available either in analog or in digital format, for the first time allow detailed geomorphological mapping of the Nevado Ojos del Saldo and its surroundings and provide a far better means of orientation for mountaineers in this very remote and deserted area in the Andes.

Application of image merging, segmentation and region-classification techniques as a new approach for the detailed thematic mapping of soil-vegetation assemblages

The paper discusses the combined use of image merge, segmentation and region-classification techniques, as a new approach in the semi-automatic mapping of land-cover types. In the first step of the procedure, a digitized panchromatic aerial photograph was co-registered with Landsat-TM images. A hybrid image set with high-spatial resolution was then produced by merging the Landsat images and the aerial photograph, through intensity (I), hue (H) and saturation (S) color transform. Using segmentation techniques, hybrid images were partitioned off into homogeneous regions, and classified according to a region-based classification algorithm. The analysis of the hybrid IHS color composite supported by field data information permitted to identify the classes on the classified image, so producing an accurate thematic mapping of different soil-vegetation assemblages in the study area. Enhanced precision and time saving are the main advantages of this approach, in comparison with the conventional visual interpretation.

A Technique for Mapping Mangroves with Landsat TM Satellite Data and Geographic Information System

The mangroves in a 2845 km 2area in the Southern Gulf of Carpentaria, Australia, were mapped from Landsat TM satellite data. The mangroves were mapped by selecting 10 training set areas in dense mangrove (100% cover), and using the maximum and minimum training set values for green, red, near-infra-red (NIR) and NIR/red to map the remaining mangroves. The accuracy of the map was improved by using ecological information about mangroves—they are found in tidally inundated areas—to derive simple rules in a Geographic Information System, to subdivide the areas labelled ‘ mangrove ’ from image processing of satellite data on the basis of nearness to water (next to water and not adjoining water), ground elevation [higher and lower than 10 m above mean sea level (MSL)] and distance from water (>2 and <2 km). Each zone was cross-checked with 1:50 000 panchromatic aerial photographs. Zones that were still mixed vegetation after applying these simple rules were further subdivided by eye. This process resulted in a map with zones identified as either 100% mangrove or 0% mangrove. The areas that were identified as mangrove were also subdivided on the basis of the three main river systems in the study area. The Norman, Bynoe and Flinders Rivers had 40·86, 10·09 and 5·42 km 2of mangroves, respectively. These areas combined with the 9·89 km 2of coastal mangrove to give a total of 66·25 km 2of mangrove in the study area.

Studying town morphology through Remote Sensing

Remotely-sensed data products have got unique advantage over conventional data-gathering techniques in the study of urban morphology. The physical parameters like built-up area density, street pattern, population density, urban structure as well as functional characteristics which can be derived from land use/land cover map, are clearly visible on aerial data products. This technique provides synoptic view of the area which makes the study comprehensive and uniform. Sequential aerial photographs and satellite imagery help in studying the growth of urban area and temporal changes in urban structure. These informations are very useful in the planning of city extension. Here an attempt has been made to study the urban morphology of Saharanpur city by using panchromatic aerial photographs on scale 1∶10,000, IRS-1B LISS II geocoded imagery on 1∶50,000 scale and photo-maps on 1∶4000 scale, and the results are very encouraging.

Vegetation maps, mapping needs and scope of digital processing of Landsat Thematic Mapper data in tropical region of south-west India

Abstract This study was aimed at assessing the scope of Landsat Thematic Mapper (TM) data for vegetation classification and mapping needs in a tropical region of south-west India. Outputs generated through common digital enhancement/classification techniques were compared with the vegetation map prepared from visual interpretation of black and white panchromatic aerial photographs with a scale of 1:15000 (approximately), in terms of extractable thematic information and cost/time incurred. It has been shown that digital processing of TM data is capable of satisfying the classification and mapping needs in the country with a reasonable degree of precision (85 per cent), in much less cost and time when compared with the aerial photographs. Supervised classification using raw data was found to be more effective in discriminating vegetation types than enhancements like band ratioing and principal component analysis. It was possible to classify forest vegetation with respect to variability in bioclimatic and st...

Visual and computer classifications of remotely-sensed images A case study of grasslands in Cambridgeshire

Abstract Study sites in Cambridgeshire have been used to assess the relative merits of Landsat Thematic Mapper (TM) data, airborne TM data and conventional panchromatic aerial photographs, for surveying the ecology and land uses of lowland Britain, with particular attention to grasslands. Techniques of computer enhancement, classification and measurement are compared with those involving visual interpretation and manual collation of map information and land-use statistics. Comparisons include measurements of the accuracy and assessments of general accessibility, ease of use, efficiency and effectiveness of the various techniques.

Forest site quality assessment by aerial photo-interpretation case study of sal forests

93 black & white panchromatic aerial photographs of 1972 on 1:20,000 scale were used for assessing the site quality of Sal forest of part of West Dehradun Forest Division, by both direct and indirect methods. The forests were stratified into 5 height and 5 density classes and according to species composition. For necessary data for the assessment of growing stock, field measurements were made on 54 sample plots of 0.1 hectare each. This provided direct indication of actual productive capacity of a particular site. According to indirect method, ground vegetation was sampled in 54 quadrats of 5m x 5m each and has been classified into statistically sound vegetation groupings by normal association analysis technique. These groups facilitated the standardisation of their photo perameters. The indicator value of the plants in a grouping was used to assess the suitability of the site. This was substantiated by super-imposing growing stock, present at that site. By combination of the direct and indirect methods, sites have been classified into 3 categories i.e., suitable, conditionally suitable and unsuitable. Suggestions have been made for management of conditionally suitable sites and the cause for unsuitability of sites are explored. Hence, interpretation of qualitative attributes of vegetation alongwith the measurements of quantitative parameters on aerial photographs have proved to be useful for site quality assessment.

A structural synthesis of Brazil, based on the study of major lineaments derived from remote sensing imagery interpretation

Notwithstanding the handicaps of equatorial haze, Brazil is nowadays completely covered by both Side-Looking Airborne Radar (SLAR) and ERTS (LANDSAT) imagery, and about 60% covered by conventional black-and-white panchromatic aerial photographs. Scattered areas, representing nearly 20% of the territory are covered by infrared false-color and by multispectral colour aerial photographs. Combined airborne gamma-ray/magnetometric surveys are available over as much as 60% of the country. This whole wealth of data has rendered it possible precisely to outline the major lineament systems. Additional field data provided the necessary back-up to unravel the origin, the mechanics and the evolution of the observed tectonic trends. Two distinct tectonic provinces were thus recognized: the “Amazon Province” and the “Atlantic Province”, in both of which the larger lineaments can be grouped into four systems: the “Northwest”, the “Northeast”, the “Paraiba do Sul” (ENE) and the “Espinhaço.” (NNE). The former two systems are more conspicuous in the Amazon Province, and are subdued and folded in the Atlantic Province, while the last two systems stand out in the Atlantic Province. Many problems of tectonic evolution and of stratigraphy are being unravelled through the analysis of such continental fracture systems.

Freshwater Wetland dynamics in South Kingstown, Rhode Island, 1939–1972

The extent and causes of changes in the fresh-water wetlands of South Kingstown, Rhode Island were determined through field work and through the analysis of panchromatic aerial photographs taken in 1939 and 1972. During this period, there was a net loss of 0.9 percent of the total area (2345.2 ha) of wetland present in 1939. Highway construction and residential development accounted for most of this loss. Approximately 17 percent of the wetland present in 1939 had changed sufficiently by 1972 to warrant reclassification. Plant succession alone accounted for 57 percent of the changes in wetland types, while man's activities were influential in 41 percent of the cases. Ninety-two percent of the natural changes in wetland types was progressive, while 58 percent of the changes induced by man and undetermined causes was retrogressive. Man's major role was to alter the water regimes and vegetation of wetlands. There was a decrease in wetland diversity as the most abundant type, wooded swamp, grew in area while the abundance of shallow marshes, meadows, and shrub swamps declined. A knowledge of wetland dynamics is essential in the management of wetlands for a diversity of wildlife and other natural values.

A Model of Natural and Man-Induced Changes in Open Freshwater Wetlands on the Massachusetts Coastal Plain

SUMMARY (1) Natural succession and man-induced changes in open freshwater wetlands were measured over a 20-yr period using panchromatic aerial photographs. Over the period 1951-71 nearly one-half of 3958-9 ha of these wetlands showed a change in vegetation class. (2) Change in wetland vegetation class due to natural succession exceeded all man-induced changes. Agriculture, cranberry culture and highway construction were the leading man-induced causes of wetland change. (3) Current public policy in the United States towards wetland protection and management treats wetlands as static entities. A partial model of wetland change is presented to suggest that wetlands should be managed as dynamic elements on the landscape.

Aerial Photographs and Forest Maps in India

A comparative case study of forest cover type mapping from 1:10,000 scale black and white panchromatic aerial photographs and by conventional ground methods of Gudem Reserve Forest of Kaghaznagar Forest Division of Andhra Pradesh Forest Department has been made. The study highlights the advantages of mapping from aerial photographs. The study indicates about the cost and time required for forest cover type mapping by aerial photo-interpretation techniques which is about half, and nearly one fourth respectively, of that required by ground methods.

Forest type mapping and volume stratification of man-made forests with aerial photographs

The use of panchromatic (black & white) aerial photographs on 1:15,000 scale for forest type mapping and evolving a suitable basis of volume stratification for man-made forests of Haldwani Division of U.P. is discussed. Forest types by species, height and density were identified and ground survey data collected in 0.1 hectare circular plots were used to evolve the basis of volume stratification by statistical analysis. The methodology used for pilot studies before regional surveys are undertaken is presented.

Textural Features for Image Classification

Texture is one of the important characteristics used in identifying objects or regions of interest in an image, whether the image be a photomicrograph, an aerial photograph, or a satellite image. This paper describes some easily computable textural features based on gray-tone spatial dependancies, and illustrates their application in category-identification tasks of three different kinds of image data: photomicrographs of five kinds of sandstones, 1:20 000 panchromatic aerial photographs of eight land-use categories, and Earth Resources Technology Satellite (ERTS) multispecial imagery containing seven land-use categories. We use two kinds of decision rules: one for which the decision regions are convex polyhedra (a piecewise linear decision rule), and one for which the decision regions are rectangular parallelpipeds (a min-max decision rule). In each experiment the data set was divided into two parts, a training set and a test set. Test set identification accuracy is 89 percent for the photomicrographs, 82 percent for the aerial photographic imagery, and 83 percent for the satellite imagery. These results indicate that the easily computable textural features probably have a general applicability for a wide variety of image-classification applications.

Frost pockets on thermal imagery

Sites of cooler micro-climate were recorded on night-time thermal imagery during overflights of a forested area in both spring and fall. The potential frost pockets appeared darkest (coldest) and ground measurements showed the sites to be as much as 5 °C cooler than another open area nearby. Comparative thermal imagery and a panchromatic aerial photograph of the study area are presented.