Preparation, Projection and Accuracy

Preparation

GeoCover LC data is prepared from Landsat TM imagery created for GeoCover Ortho. These scenes were acquired within three years of peak of greenness in 1990 or 2000. MDA's analysts use ERDAS IMAGINE geographic imaging software to classify each scene independently, employing a standard semi-automated classification approach. An initial process creates scenes with 240 spectral classes, separated by a combination of unsupervised and supervised classification algorithms. Aided by ground truth information from library, published map, and internet sources, analysts then identify spectral and spatial patterns in the imagery to assign rasters into one of 13 informational categories. Upon completion, all scenes within a Universal Transverse Mercator (UTM) zone are mosaicked together and edgematched to reduce the impact of differing seasons and years in the data set. This 13-category land cover data is processed to remove much of the speckle and noise associated with land cover categorizations based upon Landsat TM data. MDA's CLUMP routine is used to define the size of all contiguous features with the same land cover code. MDA's ELIMINATE routine removes any contiguous features of the same land cover code (with the exception of water) that are smaller in size than the standard minimum mapping unit (MMU) of 1.4 hectares, replacing these areas with the predominant surrounding land cover. Note that the procedure employed using CLUMP and ELIMINATE will not remove narrow linear features with areas exceeding the user-specified minimum mapping unit that would be removed if standard filtering procedures were used to create the minimum mapping unit.

Projection and Positional Accuracy

GeoCover LC is under independent accuracy assessment evaluation. To date, accuracies calculated through a polygon count methodology have averaged better than 70%; the polygons found acceptable by these evaluations represent over 96% of the total area sampled. The source imagery used for GeoCover LC is GeoCover OrthoTM. These data were prepared in UTM projection on WGS84 spheroid. GeoCover LC is available in either UTM or Geographic projection. Custom projections and spheroids can be discussed.

Availability

Data is currently under production, and 13-class data is complete and available for much of the world's landmass. Additional water-only data is available in many areas where 13-class data production is not yet complete.

Package deals available at a lower cost. Call for details. (Lat) and (Lon) in the item number correspond to the specific Latitide and Longitude of the cell.