SPOT images come with different levels of geometric preprocessing, divided into 2 product lines: SPOT Scene and SPOTView
level 1A: Radiometric correction of distortions due to differences in sensitivity of the elementary detectors of the viewing instrument.
Intended for users who wish to do their own geometric image processing.
level 1B: Radiometric correction identical to that of level 1A.
Geometric correction of systematic effects (panoramic effect, Earth curvature and rotation). Internal distortions of the image are corrected for measuring distances, angles and surface areas.
Specially designed product for photo-interpreting and thematic studies.
level 2A: Radiometric correction identical to that of level 1A. Geometrical correction
done in a standard cartographic projection (UTM WGS84 by default) not tied to
ground control points.
Allowing for possible differences in location, this product is used to combine the image with geographical information of various types (vectors, raster maps and other satellite images).
The default SPOT Scene delivery format is DIMAP SPOT Scene profile.
The only exceptions are 2.5-metre and 5-metre colour SPOT Scene 2A products, which are delivered in DIMAP SPOTView profile format.
Important: viewing parameters (satellite attitude, ephemeris, etc.) required for sensor-modelling orthorectification are only available in SPOT Scene profile format. These parameters are in the Data_Strip group: Data Strip Identification - Satellite Time - Ephemeris - Satellite Attitudes - Sensor Configuration - Frame Counters - Data Strip Coordinate - Models - Sensor Calibration - Bad Lines.
Reminder : the pre-processing level for orthorectification is level 1A (delivered by default in SPOT Scene profile format).
Level 3 (Ortho): Map projection based on ground control points and a DEM based on Reference3D data to eliminate distortions due to relief.
SPOTViews are delivered in DIMAP SPOTView profile format.