Polygonisation Methods - MapInfo_Pro_Advanced - 2023

Polygonisation Methods

The polygonise tool provides various methods to create polygons. Polygons are created by joining input raster cells with certain properties such as Same Value Cells, Valid\invalid Cells, Raster Extent and User Defined.

Same Value Cell

In this method, polygons are created by connecting adjacent cells having same cell values. Following is an example of same value cells polygonisation.

Observe the image on the right, all cells having same cell values are joined to form polygons. If there are scattered cells in the input raster individual polygons will be created.

You can set following options for polygons created from same cell value.

• Match Colors to Input - Select this if you want to fill the resulting polygon with the color value of the cell. ;The polygons in the vector file will be colored using the color value of the cell.
• Display Region Border Line - Polygons are closed lines which can be filled with a color, and can be used for spatial queries.

Valid/Invalid

Use this method to generate polygons that represent the valid cells in the raster and the invalid cells. In this method, all valid adjacent cells are joined to form a polygon and similarly all invalid adjacent cells are joined together to form another polygon, regardless of the cell values.

Observe the image on the right, all null cells are joined to form a polygon. In the output TAB file, the polygons corresponding to valid cells are assigned the value of 1 and the polygons corresponding to invalid cells are assigned the value of 0.

Raster Extent

In this method, a polygon is created around the extent of input raster. Select this option, if you want to generate a polygon for the entire extent of the displayed raster. This can be used to generate a perfect polygonal outline of a raster.

User Defined

In this method, a polygon is created around the defined breaks or intervals. This method works on continuous raster only. The polygon is created by connecting cells with values falling in the defined range. The user defined range is divided into equal number of breaks. For example, in a continuous raster if the values are from 1 to 100 and the Number of Intervals is defined as 4, the range is divided into 4 groups as illustrated below. Polygons are created by connecting cells whose values fall into 1 to 25 range.

Following is the list of Polygonisation methods available for different input raster field type.