Utilization of statellite Remotely Sensed Data as an Information Source for a GIS in Agricultural Resource Management
Farhad Jenabfer
Remote sensing / GIS division,
agricultural statistic & information department (ASID)
Ministry of agriculture 144155 Tehran ,Iran
Tel : (+95) 21 61 22102 fax (98) 21 650377
Abstract
Landuse/Landcover data is one of the most important data layer in any Geographic information system for agriculture resource management . the lack of Recent ,reliable
and up-to- date data for prepration of Landuse /Landcover maps has made satellite imagery ,the only practical source of up-to-date data for such studies .The study area located in north of Iran ,Gilan province was selected because of it variable vegetation and economic. Three different seasonal TM data sets acquired between1991-1994, were utilized in the , prepration of Landuse/Landcover maps which comprised seven major classes (24sub-classes) and four mixed classes. In addition some specific crops like tea and olive were also mapped. The information derived from these maps together with other data such as Topography , Transportation network, International and provincial boundaries , etc were compiled for use in the envisaged GIS that will eventually have more than 25 different information layers.
Introduction
Geographical information systems (GIS) provide an essential technology for concidering the interaction between spatial distribution of resources . GIS are now established as a common feature of both management and research in areas such as ; natural resource inventory ;mineral exploration ; primary production estimation and natural hazard evolution .
Probably the biggest problem in a geographic information system is the base maps that the software uses to perform its analysis. The deficiency of these maps or updated once is the main reason for using remotely sensed data as a consistent source of information. The results of visual image interpretation and digital processing can now fulfill a number of functions within a GIS.
This paper describes the methods used to create an agricultural GIS and problems encountered in this way
Studyarea
The area selected this project is Gilan Province, located in north of Iran, limited between long. 48 ° 35'-50°, 3' E and lat. 36'-38°, 30 N, with the total area about 15000 Km2
The role of this province national agriculture is the main reason for its selection. More than a quarter of the Rice production and about the whole production of Tea and Olive in the country obtain from this percent of this area is covered by dense, natural forests that has a significant role in wood industry.
Datasources
The use of image data to derive geographical information has long been established in the form of both topographic and thematic maps produced by the interpretation of stereoscopic aerial photographs. The sources of visual image interpretation serves to emphasize the potential serves to emphasize the potential for further improving the accuracy of digital image analysis, by including information other than spectral data (Haralick 1979). Especially in the extraction of LU/LC information for the compilation of thematic maps, visual interpretation has set a formidable precedent inters of the number of distinguishable classes. The application of satellite remote sensing to natural resource mapping has therefore often encountered resistance where there has been a history of mapping by photo-interpretation (Rivard 1990). This is especially so when land cover information is stored in GIS and then used to derive thematic products in combination with a number of other themes that are often of layer or unspecified accuracy.
Despite the legacy of photo-interpretation, remote data from satellite (especially Land TM and SPOT) have nonetheless become well established as a primary source of information in many applications related to natural resources. The inherently digital format of the data, the frequency of routine coverage of relative ease with which near-nadir imagery an e georeferenced all offer very significant advantages over photographic coverages of the same area (Konecny 179).
The Landsat satellite series which began in the 1970's is probably the most well known digital imagery gathering system. The Thematic Mapper (TM ) is a popular data source and consists of seven bands or spectral ranges. The seven bands are blue, green, red in the visible spectrum, a near infra-red, two mid range infra-reds and a thermal infra-red.
The typical TM scene covers185 X 170 km of the earth surface and is repeated every19 days. The data is organized into a matrix with each pixel covering an area of 30 by 30 meters. In each of the seven bands each pixel contains one data value representing the spectral intensity reflected from relative surface on the earth.
In this project 3 different seasonal TM data sets, acquired between 1991 to 94 and a CCT (1993) containing the whole coverage of the study area were selected to create LU/LC maps of the province.
