Updated: 17 November 2006

ACRES Landsat processing options

This page described specific processing options for ACRES Landsat data. If you are unfamiliar with the generic processing options for ACRES data, it is recommended that you first read ACRES Optical Data Processing Options.

Landsat processing levels

Main Options	Description
Orthocorrected Image	Map oriented with systematic geometric corrections refined with the use of GCPs and the GEODATA 9 second DEM. This DEM extends over Australia only. Two dimensional resampling to align with a map grid. This is the most map-accurate product, suitable for input into a GIS system.
Map Oriented Image	Map oriented with systematic radiometric and geometric corrections applied to the data. Two dimensional resampling to align with a map grid.
Path Image (USGS Level 1G)	Satellite path oriented with systematic radiometric and geometric corrections applied to the data. Two dimensional resampling to fit a specific Earth datum and map grid.
Non-standard Options
Raw Image (USGS Level 1R)	Radiometrically corrected but no geometric corrections.
Raw Data (USGS Level 0R equivalent)	No radiometric or geometric corrections. Recommended only for Groundstation interchange and for application software intended for use with very low level products.

The most common map projection for map oriented products is the Map Grid of Australia (MGA) which is a Universal Transverse Mercator (UTM) projection based on the Geodetic Datum of Australian 1994 (GDA 94). Other map projections and datums are supported.

Framing of data

Path oriented products

Path Image products are only available in full, double or triple scenes.

Map oriented products

Map Oriented and Orthocorrected Image products can be framed anywhere along the path of the satellite in the form of a variable sized rectangular "window". The sides of this rectangle are not parallel to the path of the satellite, but are aligned in the north-south and east-west map-grid direction. The product is defined in terms of a central point and dimensions in both E-W and N-S directions about that point.

For further information on "variable window" products, see Landsat Variable Window Product Characteristics.

The following table shows the different pixel sizes for different data types either as path oriented or as map oriented output.

Sensor	Pixel size for Path Oriented product	Pixel size for Map Oriented product
Landsat ETM+ and TM	30 x 30 metres	25 x 25 metres
Landsat ETM+ Panchromatic	15 x 15 metres*	12.5 x 12.5 metres
Landsat MSS	57 x 80 metres (approx)	50 x 50 metres
* Note that post-launch testing shows that Landsat ETM+ Panchromatic data is acquired by the satellite at about 18 m resolution rather than the intended 15 m. These data are resampled down to 15 m pixels for path oriented products.

Landsat 7 SLC-Off data

Data acquired by the Landsat 7 satellite after 14 July 2003 is subject to data quality issues caused by the failure of the Scan Line Corrector (SLC). The SLC compensates for the forward motion of the satellite. Consequently, this data needs to be processed in a particular way as described in ETM+ SLC-Off Products. Note that the full range of scene sizes and processing levels applicable to regular Landsat data also apply to Landsat 7 SLC-Off products.

Data Formats

These are described in ACRES File formats for Landsat Imagery.