RTV vectorizes a single channel of image data on a PCIDSK file. The vector data output from RTV is written to a vector segment in the input image file. A segment name, and a segment descriptor can be specified for the new vector segment.
Three variations of vector data can be generated: only the line boundaries of polygons (POLYINFO = LINES); only an interior point for each polygon (POLYINFO = POINTS ); or both lines and points (POLYINFO = BOTH).
If the generated vector data includes lines, then these can be generated with or without the border lines (BORDER). Border lines run along the outside edge of the selected image window. Border lines are useful in ensuring that all polygons are completely 'enclosed' at the edge of images. This is especially important if the vectors will be exported to a GIS as a coverage.
Optionally, a contour interval (CONTINT) can be specified, which determines the number of units between each generated vector contour. However, the CONTOUR program should be used to create contours from an elevation image. Contours created by RTV do NOT have attributes, and the vertex coordinates are not properly interpolated.
To prevent the generation of large amounts of vector data, it is best to use imagery which has a limited number of grey levels or large polygons. For example, a theme channel is generated by classification and mode or median filtered to remove small polygons. Use of 32-bit real imagery is not recommended since it is often composed of large numbers of different grey levels.