Update Fields - Create or update status fields in multiple tables
With this function you can create or update the status fields of multiple tables or themes. Status fields are predefined fields that can be calculated by evaluating a mathematical function. On the one hand these are feature properties (like the default fields of ArcView Length, Perimeter and Area) or complex shape measures (predefined fields of Arc4You Data like Thinness, Roughness or Convexity of polygons) that are calculated from the graphic features of a theme. On the other hand you can define data fields that are calculated based on other fields of your tables (these fields can not only be calculated for themes but for all data tables - the only predefined data field is the record ID).
The default fields of ArcView are normally updated automatically when editing a theme. All other status fields like ID and Hectares must be updated with this function each time after editing the theme. Sometimes some status fields may be missing in the attribute table or the values are not up-to-date. Use this function to ensure that all required status field are available in the active themes and the values are updated.
Note: The decimal point itself consumes one place of the field width, i.e. the number of possible pre-decimal places results from the total field width minus the number of decimal places minus 1.
Warning: The option Selected should not be used together with Update Field Width, because new fields will be created and the field values of the not selected records would get lost.
All results are basically calculated in the map unit of the view (seeView - Properties - Map Units). At the calculation of Acres or Hectares the area will be transformed accordingly. If the map units are unknown (e.g. for tables), it is assumed that the coordinates are in meters. If the map units are incorrect, the results will be wrong.
If a theme is in world coordinates (decimal degrees) and is displayed in a different projection (seeView - Properties - Projection), the calculations are made in the units of the projection. If the projection is unknown (e.g. for tables) and the data is stored in decimal degrees, all results will be wrong.
Warning: The status fields of projected themes (and themes that are not stored in meters) should therefore never be updated via the attribute table but only in the view (only then the map units or projection are known and the results will be correct).
The data fieldRecord ID can be created or updated in all themes and tables. It represents the internal record number of the table as it is displayed in ArcView spreadsheets (starting at 0). It must be updated after deleting or adding records. It is constantly changing during editing and should therefore not be used as an index or for joins.
© 2003 WLM Klosterhuber & Partner OEG