The region inspection function, Using the region inspection function – Pitney Bowes MapInfo Vertical Mapper User Manual
Page 134
The Region Inspection Function
132
Vertical Mapper 3.7
Each statistical parameter calculated for each open and active grid is written into a separate column
of the region table and given a default column name consisting of both the parameter name and the
grid file name.
Note The number of samples taken along the line is determined by the Cross Section: No of
Samples parameter in the Preferences settings. The default is 100. To change this value,
choose the Vertical Mapper, Preferences command and enter a new number in the No of
Samples box. For more information about Preferences, see
.
The Region Inspection Function
It is important to understand the manner in which Vertical Mapper calculates area using grids. Every
grid file is constructed of cells of equal area, as determined from the unique coordinate system
specifications to which the grid has been projected. However, a grid in any coordinate system is only
truly accurate, in terms of real spherical (ground) distance, along the line of standard parallels.
Therefore, as you move farther away from the standard parallel, the actual ground area of a grid cell
becomes less accurate (usually it is larger than its real spherical area). While in most cases the error
will not be significant, if area is important, you have two options to minimize this error:
•
Ensure that the grid is always projected to an appropriate coordinate system that is relevant to
the geographic region of interest.
•
Using the Vertical Mapper Contour function, convert the grid file covering the area of interest to a
MapInfo region and then query the region to obtain MapInfo Professional’s spherical-based area
calculation.
Using the Region Inspection Function
The Region Inspection function updates a MapInfo table of regions with new columns of values
taken from one or more geographically coincident grid files. The process inspects the grid file
underlying each region, returns a selected number of statistical parameters calculated from the
range of grid values lying within each region, and writes the value to a new column in the region
table.
1. Open a MapInfo table of point data and the grid files from which the information will be extracted.
2. In the Grid Manager, click the Analysis button and choose the Region Inspection command
.
3. In the Region Inspection dialog box, choose the appropriate region table to update.
4. In the Select Attributes to ADD for All Active Grids section, choose all of the statistical
parameters that will be calculated for each region and written into the region table.
5. Click the OK button.
Each statistical parameter calculated for each open and active grid is written into a separate column
of the region table and given a default column name consisting of both the parameter name and the
grid file name.