Remote Sensing is the art of acquiring information about an object without coming physically in contact with it. The data remote sensing is used in acquisition of information from the remotely sensed images. Image data, ground data, auxiliary data are some of the data in remote sensing .
The data remote sensing can be divided into:
• Digital data remote sensing : An image having a continuous spread of color or a tone of gray is called analog image whereas if the image contains a host of divided cells, each having value of average intensity in integer format and the value of each cell is represented by the center it is called digital image. Sampling is the name of the process of dividing the image into a number of cells and the transformation of analog images into digital images is called quantization.
• Auxiliary data remote sensing : An image is made up of numerous files. Each file consists of numerous records. Except the image data, all the other data are called auxiliary data. Auxiliary data consists file description, image data, platform, sensor, processing of data and other various kind of data.
• Ground data remote sensing : The observation of ground features, measurement of ground details and information about the actual status of the earth helps to relate remote sensing data and the concerned object on the ground. Ground data is collected at the time of acquisition of data by the remote sensor or when the environmental condition remain static for some time. Ground data is useful for designing of sensors, calibration and validation and other uses.
• Ground positioning data: For perfect geometric correction, coordinates of the ground control points are needed. Ground control points of the image should coincide with the ground control points of the ground and the measurement of both ground and image coordinates are done. Both topographic maps as well as Global Positioning System (GPS) are used to measure the coordinates.
• Map data used in remote sensing : In remote sensing three kind of maps are used which are:
• Topographic map is useful for creating digital elevation model.
• Thematic map consist of land use, vegetation map, pedological map and geological maps.
• Socio-economic maps provide political informations, tranportation route and network, distribution of population, agricultural and industrial information, tax related queries and many more.
• Digital terrain data used in remote sensing : Data about topography like alitude, slope and so on are included in digital terrain data. The terrain characteristics is shown by four ways:
• Grid data
• Contour lines
• Random point data
• Surface function
Calibration and validation of data remote sensing :
Calibration is defined as the correction of the data observed by the sensor into total irradiation, reflectance or proper temperature. It is divided into ground calibration and on-board calibration. Validation is divided into instrument specification, physical quantities and practical usages. Validation is done in relation to the ground data.
Remote sensing data and Geography Information System (GIS)
Since both remote sensing and GIS give information about features on earth surface, almost all the GIS softwares uses data remote sensing for a number of reasons like continuous view of the region or extracting any other information.
Thus, data remote sensing is an important part of remote sensing .
Digital Orthophotography