Detection of Land Use Changes using Remote Sensing and GIS
Kam, Suan Pheng and Foo, Lay Kuan
School of Biological Sciences,
University Sains Malaysia, 11800 Penang, Malaysia
Abstract: A thematic map produced from digital classification of a SPOT multispectral subscene over a portion of south Johor, Malaysia, was brought into a GIS to assess classification accuracy using a land use map produced from aerial photo interpretation and ground checks. Percentage accuracy’s were found to be generally lower (by 5.3 % to 51.2 %) compared to accuracy’s assessed based on homogeneous areas test. Changes of land use were analyzed by GIS overlays of the 12974 and 1986 land use maps rather than with the interpreted SPOT data because of the generally low classification accuracies. The problems arising from analyzing changes between maps of different land use and land cover categories were pointed out.
Introduction
Remote Sensing techniques have proven useful for gathering information about the natural resources on a large-scale basis, such as for a whole country. The Malaysian Ministry of Agriculture has been using aerial photo interpretation for land use mapping for Peninsular Malaysia. With its aggressive land development policy, there is great need for timely information on the agricultural and forestry resources of the country. With the increasing availability of high resolution satellite imagery, and as the land information handling capabilities within the country is modernized, it is opportune to explore the potential of remote sensing and geographical information systems (GIS) in information gathering and updating of its resources. This paper reports an attempt to bring over a land cover map from classification of SPOT imagery into a GIS database and discusses a number of issues relating to reconciliation of land use maps of different times from different remote sensing sources.
Background
The land use ,maps of Peninsular Malaysia produced in 1966 and again in 1974 by the Malaysian Ministry of Agriculture were based on visual interpretation of aerial photos at 1:25,000 scale (Siew,1969: Wong,1976). Color maps as 1:126,720 scale were published for the two surveys. In 1980/81, aerial photos were flown at 1:40,000 to update the 1974 land use maps. The 1974 manuscripts were used as the base for land use changes exceeding 40 ha in size. By then, the Ministry had acquired a COMARC GIS for digitizing the interpreted maps and to serve as a data retrieval facility whereby maps of any selected area can be plotted on demand with area summaries.
It would be expected that the use of computer-assisted mapping would accompany or be accompanied by the use of computer-assisted techniques for processing of remote-sensed data. However, the use of remote sensing techniques other than aerialk photography for land use mapping is at present still experimental. A number of issues would have to be faced in making the transition from the conventional methods to the new, particularly in the context of the Malaysian situation. These Include :
- The utility of remotely-sensed data such as satellite imagery for land cover mapping, Particularly with respect to specificity and classification accuracy.
- Availability and timeliness of remotely-sensed data for a complete coverage of Peninsular Malaysia, if not the whole country.
- Registration with former maps for detection of land use changes and for related spatial analyses on the GIS.
The first of these issues is being actively researched by the various institutions in the country which have recently acquired image processing capabilities. The second issue would hopefully be facilitated with the impending functioning of the Malaysian Center for Remote Sensing for centralized acquisition of remotely-sensed data. The third issue, though minor in comparison to the first two in terms of research and data acquisition effort, is nevertheless important in view of a potentially growing user community with data needs for a wide range of GIS applications. This was borne out in the present study by the authors as part of the ASEAN-USAID Coastal Resources Management Project when faced with the task of reconciling land use maps of two different times at different levels of interpretation.
