Update Feature Sizes

Data sets created by ARC/INFO include feature size attributes calculated when the topology was established. Line themes include the length of each line feature (ARC/INFO arc), while polygon features include the area and perimeter of each polygon. However, as these measures are based on source data co-ordinates (ArcView Map units), the size of features defined by decimal degree co-ordinates has no meaning. For data sets created as new shapefiles, e.g. by importing spatial ASCII data, no feature size attributes are calculated and included. Hence, for classification of features based on size, or to make calculation involving a feature size, e.g. areal density, attributes showing real feature sizes must be included.

To achieve this, make the theme(s) to update active and choose the Update Feature Sizes menu choice in the Theme menu. This utility will check whether the active theme(s) has proper feature size attribute fields, and if not it will create and add such attribute fields. Then the size of each feature will be calculated and entered into the proper attribute field records. For Line themes the feature size attribute field is named "Length", while for Polygon themes the feature size attribute fields are named "Area" and "Perimeter". The feature sizes are in Map units and are specified with 3 decimals.


You must have write access to the files of the active theme to use this menu choice.