Landsat 8 and DEM for land cover/land use : necessary ?

[Redoxi]

I've read in several papers that in order to do a better land cover / land use identification with Landsat images, it is better to project them on a DEM and ortorectificate then.

 

When I read the Landsat 8 images specifications,  I see that they are already ortherectified. 

 

So my question is : do I need to do this step, or can I use Landsat image "as is" ?

 

Would the response be different for Landsat 5/7 and Landsat 8 ?

 

Thanks in advance.

I

[dr_s1ngh]

u need not to do orthorectification for Landsat 8 OLI images. becoz these images are rectified by the USGS.

[deepgis]

For LANDSAT 5 and 7. Please go through the matter below and do accordingly-

Standard Terrain Correction (Level 1T) - provides systematic radiometric and geometric accuracy by incorporating ground control points while employing a Digital Elevation Model (DEM) for topographic accuracy. Geodetic accuracy of the product depends on the accuracy of the ground control points and the resolution of the DEM used:

• Ground control points used for Level 1T correction come from the GLS2000 data set. DEM sources include SRTM, NED, CDED, DTED, and GTOPO 30

Systematic Terrain Correction (Level 1Gt) - provides systematic, radiometric, and geometric accuracy, while employing a Digital Elevation Model (DEM) for topographic accuracy.

• Landsat 7 scenes over Antarctica are the only data processed to an L1Gt. The Ramp V2 DEM is the elevation correction source.

Systematic Correction (Level 1G) - provides systematic radiometric and geometric accuracy, which is derived from data collected by the sensor and spacecraft. Geometric accuracy of the systematically corrected product should be within 250 meters (1 sigma) for low-relief areas at sea level.