Search

In gridding method dialogs, search options control which data points are considered by the gridding operation when interpolating grid nodes. To access the search options, if available with the gridding method, click the Advanced Options button on the Gridding page. If searching is available with the selected gridding method, a Search page appears in the gridding options dialog. If search options are not available for a gridding method this means that all the data points from the boundary file must be used when calculating the grid.

Search rules define the number of points included in interpolating a grid node value. Uncheck the No Search (use all of the data) option to enable the search rules edit controls. Search rules limit the number of data points to include in the interpolation at each grid node. Search rules work in concert with the Search Ellipse. The Search Ellipse specifies the size of the local neighborhood in which to look for data, and the Search Rules specify the number of points to actually consider within the neighborhood.

If the number of data points defined by the Minimum number of data in all sectors is not found within the Search Ellipse distance, a blanking value (special null value) is assigned at the grid node. Blanking values indicate that insufficient data existed to satisfy the search criteria at that particular location.

Use the Search tab in the gridding method options dialog to select which data

are included in grid calculations.

Search Options

The No Search (use all of the data) option tells MapViewer to use all data when interpolating each grid node. Uncheck the No Search box to activate the search during the gridding process.

The Number of sectors to search option divides the search area into smaller sections to which you can apply the following search rules. You can specify up to 32 search sectors.

The Maximum number of data to use from ALL sectors value limits the total number of points used when interpolating a grid node.
The Maximum number of data to use from EACH sector value specifies the number of points to be used from each sector.
The Minimum number of data in all sectors (node is blanked if fewer) value assures that the specified number of points are encountered when interpolating a grid node. If the minimum number of points is not found, the blanking value is assigned at the grid node. Data points beyond the nearest points in a quadrant are ignored even if the data points in another quadrant are farther from the grid node being calculated.
Blank node if more than this many sectors are empty assures that if more empty sectors than this value are encountered, the blanking value is assigned at the grid node.

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.