POTENTIAL USE OF HIGH RESOLUTION SATELLITE IMAGERY FOR LAND USE SURVEYS

摘要

Conventional area frame sampling survey, which is a technique of agricultural probability sample survey, is costly and time-consuming activity; requiring aerial photograph mosaics, paper base satellite image products and existing maps. It involves laborious and meticulous activities to delineate strata, primary survey units (PSUs) and segments with identifiable physical boundaries. The aim of this study was to evaluate the potential of using high-resolution (15m) Aster image data instead of aerial photographs for improving the area frame sampling survey method through reducing costs and efforts. High-resolution image (3,2,1 false colour composite) was visually analysed in ERDAS Imagine for predefined survey variables to delineate survey frame limits, strata and PSUs. Segments (Last stage sampling units) were formed by means of UTM grids with their coordinates instead of using identifiable physical boundaries. Image enlargements of sample segments were prepared for ground survey. An extensive fieldsurvey was carried out to evaluate the applicability of the survey frame. Survey frame limits, strata and PSU boundaries can be delineated conveniently for Aster image by visual interpretation using image-processing software. UTM grid for segmentation reduced time and effort in frame construction. Aster image can be used as a substitution for topographic maps for ground survey since it shows the roads and many other necessary details to find the locations of sample segments. The agricultural plots in this study area can easily be identified on an Aster image enlargements and this leads to reduce costs by making use of often-outdated aerial photos. The Aster image used to develop an area frame saved cost of materials as it was downloaded free of chargefrom the web. In developing countries, where up-to-date materials are lacking, use of aster images fulfils the need of such materials for area frame construction. The completely automated procedure of using Aster images in image processing saves more time and cost involved in different steps of area frame sampling survey, opposed to the time and cost involved in manual procedure. Use of high-resolution Aster images, therefore, constitutes a very important potential improvement and simplification for area frame construct/on since it avoids the laborious and meticulous work required for conventional methods.