The Search Ellipse defines the local neighborhood of points to consider when interpolating each grid node. This defines the distance in data units from the grid node that MapViewer looks to find data points when calculating grid nodes. Data points outside the search ellipse are not considered during grid node interpolation.
Elliptical searches do not impart extra weight to data points in the various directions, but do search farther along one ellipse axis. The default Search Ellipse is circular; meaning that MapViewer looks the same distance in all directions.
Search ellipses are specified by defining the ellipse radii and the angle for the ellipse.
Radius 1 and Radius 2 are positive values indicating the distance in data units.
Angle is the inclination between the positive X axis and the ellipse axis associated with Radius 1. This can be any value between -360 and +360 degrees.
Blanking values indicate that insufficient data existed to generate a grid node value at that particular location based on the specified search rules. For example, if you inadvertently set your search ellipse size to be smaller than half the distance between your data points, a significant number of grid nodes may be blanked.
Although not required, in most cases it works well to set the search ellipse ratio and direction to coincide with the anisotropy ratio and direction. For more information on anisotropy, see Anisotropy. Note that not all gridding methods contain anisotropy options.
See Also