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Landsat 8 L1 products are "Terrain Corrected",

that said it means that are they already "topographically corrected", like both words are synonyms or you need to apply correction techniques as well? (eg i.topo.corr for Grass)

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Old question, but I think a clarification might be useful generally.

  • The term topographic correction should mean correcting for slope illumination. For example for the purpose of cover type classification it is desirable, that the image color is function of the cover type and not the illumination angle etc., but slope side towards the sun is lighter and the other is darker. Topographic correction tries to remove this effect - as does the i.topo.corr GRASS GIS command. This type of correction is usually not part of level-1 processing, but may (or may not) be part of level-2 processing chain (atmospherically corrected products).
  • Term terrain correction is usually connected with geometric effects of terrain, i.e. correcting shift of surface feature pixel positions in image due to terrain elevation and observation angles from the satellite. The terms are often mixed, but in the description of Level-1T products, it has this geometric meaning. See descriptions in Table 2-1 on page 3 in section 2 of document https://landsat.usgs.gov/sites/default/files/documents/LSDS-1656_Landsat_Level-1_Product_Collection_Definition.pdf
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According to section 10.2 Level 1 Algorithms from NASA's Landsat 7 Science Data Users Handbook, all Landsat 7 Level 1T products are corrected for terrain effects (see also Figure 10.4). The same applies for Landsat 8 data of level 1T which refers to Standard Terrain Correction (Level 1T).

The correction(s) might not be perfect. Thus, one can, in theory, undergo a more detailed process for ortho-rectifying Landsat L1G products by using a DEM of higher resolution/quality than the well known DEMs SRTM or/and ASTER GDEM(2) both of which can be considered, depending on the application, as being coarse.

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  • Then can I conclude If I use 1T data then no need of topographic/illumination correction using coarser DEM like ASTER, SRTM etc?
    – SIslam
    Aug 16 '16 at 17:45

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