R. M. Fuller

The UK Land Cover Map 2000: Construction of a parcel-based vector Map from satellite images

Abstract Land Cover Map 2000 (LCM2000) is a thematic classification of satellite image data covering the entire United Kingdom. The map updates and substantially upgrades the Land Cover Map of Great Britain (LCMGB), made in 1990–92. This paper outlines the character of the map through a description of its specification, production and outputs. The paper is aimed at users of LCM2000 and derived data who need to understand more of the map and its characteristics. The paper also outlines plans for making data available to researchers and applied users. The most important development in LCM2000 was the spectral segmentation of images to generate vector land parcels. Land cover was then identified by the spectral classification of the image data in these parcels. Classification used specially developed procedures which exploited known spatial, spectral and contextual characteristics of land cover. The resultant GIS incorporates, within its vector structure, detailed attribute data which record parcel-based land cover, plus information on class probabilities, data on within-parcel heterogeneity, information on landscape structure and context, cover information from LCMGB, together with a record of each parcels processing history.

The characterisation and measurement of land cover change through remote sensing: problems in operational applications?

Abstract This paper examines issues surrounding the detection, measurement and characterisation of landscape changes by remote sensing and other means. First it compares the remotely sensed Land Cover Map of Great Britain (LCMGB), 1990, with the UK Land Cover Map 2000 (LCM2000). Then it considers the more general circumstances where users compare any two thematic maps incorporating independent inaccuracies, to record changes. The paper concludes that the measurement of small to medium scale changes over large areas requires levels of precision in mapping which are near impossible to achieve with satellite image classifications alone; indeed they may be difficult to achieve in any form of survey unless it is tailor-made and rigorously applied specifically to the recording of real changes. The paper argues that users of all such data products therefore need to treat with extreme caution their maps of differences and their conclusions about change. It suggests that users need also to develop intelligent approaches, which draw upon a broader knowledge of the directions, patterns and scale of the changes to be recorded, in order to refine their assessments.

Contextual correction: techniques for improving land cover mapping from remotely sensed images

Large area land cover mapping is an important application of remote sensing. A digital land cover map of Great Britain has recently been compiled by supervised classification of Landsat Thematic Mapper data. The work has involved development of a range of post classification procedures to correct contextual errors associated with the use of spectral classification algorithms. This paper describes these procedures and examines their effects upon the map product including a comparison with field survey data.

The use of airborne remote sensing for extensive mapping of intertidal sediments and saltmarshes in eastern England

Airborne remote sensing with a Compact Airborne Spectrographic Imager (CASI) and a Daedalus Airborne Thematic Mapper (ATM) has been used to map sediment types and biotic associations for the intertidal zone along 270 km of coastline from the Humber Estuary to North Norfolk, UK within the LOIS BIOTA (Land-Ocean Interaction Study, Biological Influences On interTidal Areas) programme. This allows field-based biotic and sedimentary information to be extrapolated to provide information for modelling the coastal processes of erosion and accretion. The method adopted for image classification was unsupervised clustering which was used to map an extensive area (476 km 2 ) of the exposed intertidal zone at a spatial resolution of 5 2 5 m pixels. Ten broad classes of intertidal sediments and vegetation have been mapped with approximately 70% correspondence with ground data.

Geometric correction of airborne scanner imagery by matching Delaunay triangles

Abstract A major factor limiting the usefulness of airborne scanner imagery such as ATM has been the inability of conventional geometric correction procedures to remove high frequency distortion induced by platform and relief effects. An algorithm is described which uses matching Delaunay triangles to achieve a form of geometric correction that can cope with high frequency distortion. Early experimental results show that the procedure has the capacity to correct images which exhibit very complex patterns of distortion.

Classification of TM imagery in the study of land use in lowland Britain: practical considerations for operational use

Abstract Thematic Mapper (TM) data were tested in a classification of general land use, but especially semi-natural habitats, in an intensively-farmed area of lowland Britain. The range of classes which could be identified, and the accuracy of the classifications which were much enhanced by the use of multitemporal (summer and autumn) data. Results were assessed by comparisons with census statistics, by scoring classifications field-by-field, and by comparing the classmap, pixel-by-pixel, with check-maps. In the cereal farming areas which make up most of the arable lowlands of Britain, TM classifications can provide accurate cover and distribution data, at the scale of the individual field, for most major land uses. No other method could realistically do this. With some caution, such methods might be adopted for routine operational use.

A comparison of land cover types in an ecological field survey in Northern England and a remotely sensed land cover map of Great Britain

Earth-orbiting remote sensing satellites have important roles to play in resource assessment and monitoring changes in land cover. However, there will often be a need to relate the land cover types identified from the classification of satellite imagery to other classifications of land cover, and particularly those familiar to practical conservationists working in the field. This paper compares the land cover types recognised in the first remotely sensed land cover map of Great Britain with those of a widely used ecological field survey method (the Phase-1 survey technique of the former Nature Conservancy Council of Great Britain) within a sample area of 188 km2 in Northern England. Digitised field maps were combined with the remotely sensed land cover map within a geographical information system (GIS) to produce a matrix of correspondence linking the two classifications. The results are discussed with an emphasis on the factors underlying the observed differences between the two sets of map data. Two potential applications of the land cover map are investigated — first in the mapping of dwarf shrub vegetation (a habitat which has declined over the last 50 years), and second in the detection of coniferous afforestation (a significant cause of semi-natural habitat loss in upland Britain).

The Availability of Landsat TM images of Great Britain

Abstract The loss of Landsat 6, at launch, and the ageing sensors on board Landsats 4 and 5, enhance the value of existing TM images. This letter shows that 88 per cent of Britain was imaged as cloud-free scenes or quarter scenes, in both the summer and winter of 1988-1990 and 97.5 per cent was imaged on at least one date. Acquisitions in 1991-1993 have been few.

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.

A CORINE map of Great Britain by automated means. Techniques for automatic generalization of the Land Cover Map of Great Britain.

The European Commission (EC) programme ‘Co–ordination of Information on the Environment’ (CORINE) includes a project to map the land cover of member states. The CORINE map is essentially one which combines land cover and land use, giving 44 separate classes, in vector, displayed at a scale of 1:100000 with a minimum mappable unit of 25 ha. The Institute of Terrestrial Ecology (ITE) has compiled a digital land cover map of Great Britain (LCMGB) from classification of Landsat–TM data, resampled to a 25 m raster, with a minimum mappable unit of 0.125 ha and 25 cover types. This paper describes a pilot study which demonstrates the successful spatial generalisation with contextual interpretation to convert the LCMGB to CORINE specifications using semi–automated techniques within a GIS environment.