Satellite data

Satellite data

Data input   involves conversion of data from maps, field observations, laboratory data, processed satellite images and aerial photos into digital format. Data input to GIS can be either manual, semi-automatic or fully automatic. In manual digitization, the map is fixed on a digitizer board and lines are traced using a cursor which converts the analog data to digital format. In automated methods the map is scanned to generate a raster data set which is converted to vector data set using raster to vector conversion softwares.

•   Digitizing data using a digitizing tablet (i.e., paper maps),

•   Scanning data using a flatbed or drum scanner (i.e., paper maps),

•   Using a computer keyboard or mouse (i.e., numbers, street and/or place names)

•   GPS (i.e., coordinate data such as latitude, longitude) and

•   Digital cameras (i.e., structure photographs)

(i) Spatial data – It consists of maps which have been prepared, either by field surveys or by the interpretation of remotely sensed data. E.g. Soil map, geologic map, land use map, village map etc., The spatial data may be either point data (wells, railway stations, buildings), line data (highways, rivers, elevation contours, pipelines, powerlines etc.,) and areal data (soil, land cover, water bodies and vegetation)

(ii) Non – spatial data –It constitutes of attributes that are complementary to the spatial data For example, the attributes for a soil category could be depth of soil, texture, erosion, drainage etc.,

Data Model

The data model represents a set of guidelines to convert the real world (called entity) to the digitally and logically represented spatial objects consisting of the attributes and geometry. There are two major types of geometric data model; vector and raster model