Sources of Geographic Information & Data in Remote Sensing and GIS
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The most important and expensive component of the GIS is Data which is generally known as fuel for GIS.
GIS data is combination of graphic and tabular data.
Perhaps the most important component of a GIS is in the part of data used in GIS.
Types of GIS Data:
GIS data can be broadly described as – Spatial data and Non-Spatial data.
- Spatial Data:
Data that define a location of a geographical features.
Spatial data is the physical representation of earth features. It represents the location, size and shape of the object in the earth i.e. building, ponds, mountains, administration, and boundaries etc.
These are in the form of graphic primitives that are usually either points, lines, polygons or pixels. .
Spatial data can further be divided into two types – vector and raster data.
- Raster Data: Raster data is made of pixels. It is an array of grid cells with columns and row. Each and every geographical feature is represented only through pixels in raster data.
- Vector Data: Vector data represents any geographical feature through points, line or combination of these.
Sources of Spatial Data: Hard copy maps, aerial photographs, remotely sensed imagery, point data, samples from surveys, and existing digital data file.
- Non-spatial data:
Data that describes the characteristics of a geographical feature.
Non spatial data also called attribute or characteristics data.
Non-spatial data are represented in table formats. For example, the administrative boundary table has population information, district name, provinces, sex ratio etc.
Sources of Non-Spatial Data: GIS data from Libraries, National and international mapping Agencies, elevation data, Bathymetry Data, Georeferenced images, time series Multispectral Satellite images, Town planning and management departments, State and national agencies and detailed district or Municipal data.
Difference between Spatial Data and Non-Spatial Data
Describes the absolute and relative location of a geographic feature.
All types of data objects or elements that are present in a geographical space or horizon.
Satellite images and scanned maps help to obtain spatial data.
Describes the characteristics of a geographical feature.
Characterizes of geographical features that are quantitative and qualitative in nature.
Town planning and management departments, Libraries, National and international mapping Agencies help to obtain non-spatial data