GeoMedia Grid has a number of Statistical Analysis commands. Below is a short description of the three most prevalant commands:
1. LOCAL SCAN
Local Scan creates an output layer of local summary statistics based on the input layer cell values found within a scanning window.
Inputs
Local Scan works best on a Source layer of sparse data or discrete data points, rather than continuous data. Exceptions to this are the Statistic options Average, Median, Maximum and Minimum, which work well with continuous data sets such as Digital Elevation Models (DEMs). The Source layer data type can be either fixed point or floating point.
A Mask layer can be specified to limit input values to defined areas. When a Mask layer is used, statistics are computed only for those cells of the Source layer that correspond spatially to nonVOID cells in the Mask layer.
Results
Local Scan produces a Result layer in which the value of each cell is the summary statistic computed for the corresponding cell of the Source layer. The Result layer will be of fixed point data type when the Diversity and Density statistics are computed. When any other statistic is specified, the Result layer will be the same type as the Data layer.
2. RANDOM
layer having a randomly determined subset of the data of the input layer.
Inputs
The command requires one input layer, of fixedpoint or floatingpoint values.
Results
The Result layer has the same extents, projection, and cell resolution as the Source layer, and is of the same data type.
3. ZONAL SCORE
The Zonal Score command creates a grid layer of summary statistics for geographic zones.
Inputs
The command requires two input layers: a Source layer and a Data layer.
The Source layer defines the geographical zones within which the statistics are computed. The Source layer must be of fixedpoint values. Examples of zones include residential neighborhoods, zoning districts, agricultural fields, soil types, climatic regions, species habitats, or census tract blocks.
The Data layer provides the data values used to compute the zonal statistics. The Data layer data type can be either fixedpoint or floatingpoint. For example, a Source layer representing soil types might be used with Data layers showing moisture content, contaminant concentrations, crop yields, land use, or soil invertebrate population densities.
Results
The values of the Result layer are the statistic, computed using the values of the Data layer, for each zone defined by the Source layer. When the Diversity or Density statistic is specified, the Result layer will be of fixed type. When any other statistic is specified, the Result layer will be the same type as the Data layer.
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