Landsat Geometric & Radiometric Specifications

Geometric Specifications

The positional accuracy of ACRES Landsat products is dependant on the sensor, level of processing, spatial resolution of the Digital Elevation Model (DEM), and the source of Ground Control Points (GCPs), used in the ortho-correction procedure. The accuracy figures specified for Ortho products in the following table are applicable to products produced using the National Mapping 9" DEM, and Supplemental Control Points (SCPs), derived from controlled full length Landsat 7 passes of the Australian continent.

During the procedure of ortho-correction, the effects of relief displacement are corrected with the use of a DEM. The planimetric accuracy of products acquired over areas with very high local relief areas, and/or using a large viewing angle, may exceed the quoted accuracies due to spatial resolution limitations of the 9 second DEM.

The quality of the ortho-correction can be limited by the ability to successfully mark well distributed control points within the image. This is typically limited by the availability of clear land targets within the image being processed.

Please contact ACRES Customer Services if you have any of the following requirements:

• Your own DEM to be used for ortho-correction.
• Your own maps or GCPs to be used as ground control source, including areas where SCPs are not available eg. New Zealand and Papua New Guinea.
• You are ordering several contiguous scenes that will be mosaicked.

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Radiometric Specifications

Scene histograms provide the best indication that ACRES has correctly, relatively calibrated the radiometry. Relative radiometric calibration is variable and scene dependent but should normally meet the following limits which ACRES uses to check its products.

Where a scene's parameters does not meet any of those listed below, then the problem will have been discussed with the client and the outcome noted.

General Parameters

• Forward and reverse gain values will be around 1 and numerically relatively close.
• The histogram of any band should not be excessively narrow or clipped.
• The ‘total sync loss’ value should read zero (0).

For Landsat

• The mean band value will range from around 25 to 100 for bands 1-5 and 7.
• Band 6 may have a higher value but should not normally exceed 150.
• Note that all LS4 MSS data contains coherent noise, and LS5 TM and MSS data between May and August 1995, may exhibit noise due to the early time of overpass.