Types of Raster Data: SPOT, DEM, Digital Orthophotos, Binary Scanned Files and Graphic Files (Especially for GATE-Geospatial 2022)

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There are many types of raster graphics:

This Diagram Shows Types of Raster Graphics

1. SPOT Satellite Imagery

Remotely sensed satellite data are recorded in raster format.

Spatial resolution varies:

  • 30 m. for Landsat 4 and 5 (use the Thematic Mapper scanner) , and Landsat 7 (use Enhanced Thematic Mapper-Plus, ETM + scanner) .
  • 20 m. for SPOT images (multi-spectral sensor) , and 10 m. for SPOT (Panchromatic sensor) .
  • 4 m. and 1 m. for IKONOS Multi-spectral and Panchromatic images respectively.

The pixel value in a satellite image represents light energy reflected or emitted from the Earth՚s surface.

The measurement of light energy is based on electromagnetic spectrum.

Satellite images can be displayed in black and white or in color.

This Diagram Shows Landsat TM Bands
This Diagrma Shows Composite Color Image

2. Digital Elevation Model (DEM)

DEM consists of an array of uniformly spaced elevation data.

DEM are produced from:

  • A stereo-plotter and aerial photograph with overlapping areas.
  • Satellite imagery such as SPOT stereo model using special software.

3. Digital Orthophotos

They prepared from aerial photograph or other remotely sensed data.

Displacement caused by camera tilt and terrain relief has been removed.

They are geo-referenced and can be registered with topographic and other maps.

This Figure Shows Digital Orthophoto

4. Binary Scanned Files

Scanned image containing values of 1 and 0

Maps to be digitized are typically scanned at 300 or 400 dpi (dot per inch) .

5. Graphic Files

Maps, photographs, and images can be stored as digital graphic files.

  • e. g. TIFF (Tagged Image File Format) ,
  • GIF (Graphic Interchangeable Format) ,
  • JPEG (Joint Photographic Exports Group) , etc.
  • GeoTIFF is a geo-referenced version of TIFF format.
Picture Shows Graphics File in Raster Data

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