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The ArcInfo Ungenerate file format provides a fairly simple means of transferring data to other GIS systems in an ASCII file format. As the format makes it somewhat awkward to transfer data which includes annotation or multiple attributes you might also like to examine the MapInfo MIF/MID format as an alternative. There are three types of Ungenerate files, namely LINE files, POINT files and POLYGON files. Data consisting solely of line work (e.g. roads) would be written out as a LINE file. Point data (e.g. tourist sites) would be written out as a POINT file. Data that consist of closed polygons can be written out in one of two forms:
With the line work for the polygons in a LINE file and the label points (seeds) in a POINT file. The user can then reassemble the polygons from the lines and points, or, |
As a POLYGON file that contains both the line work and label points. This format is slightly more complex.The three file formats are described in more detail below: |
POINT UNGENERATE FILES (*.POI FILES):
Each record in the file contains three numbers. The first is the ID number of the point, the second the X co-ordinate and the third the Y co-ordinate. A typical portion of the file would thus look like:
1 200567.345 456543.234
2 257658.458 462789.435
3 261340.456 470600.370
etc.
LINE UNGENERATE FILES (*.LIN FILES):
For each Arc (individual line segment of a maximum of 500 points) the file will contain the ID number on the first line, XY co-ordinate pairs on the second and subsequent rows that define the line, and the word END to terminate the Arc. A portion of the file would thus look like:
1
456234.612 856234.611
456981.347 867923.456
457840.608 866454.333
489333.444 890544.677
END
2
645700.957 700623.787
653000.456 710756.854
632977.234 715000.746
etc.
POLYGON UNGENERATE FILES (*.POL FILES):
For each polygon the file will contain an ID number and an XY co-ordinate pair for the polygon label point (seed). The second and subsequent rows will contain a list of XY co-ordinate pairs defining the Arc(s) that make up the border of the polygon. Note that if more than one Arc defines the polygon then the last point on one Arc is also the first point on the next so these co-ordinate pairs will occur twice on adjacent rows in the file. Please note that island polygons (e.g. an island in an enclosing loch) are described twice - once in their own right as above, but they are also described under an ID flag of -99999. This is because some GIS systems require special treatment of such islands. You can ignore or delete the flagged island polygon records if the normal description alone is sufficient.
LOOK UP TABLES:
In some simple cases the ID numbers of the lines, points or polygons are sufficient to hold the attribute information, but the ID is restricted to a single integer number. Thus an additional file will often be provided containing the ID numbers and one or more attribute codes for the feature. These additional files will normally be given a .TXT extension. The fields will normally be separated by a ':' delimiter. For example: ID NAME ADDRESS1 ADDRESS2 POSTCODE 1 :SHERATON HOTEL:LOTHIAN ROAD:EDINBURGH:EH1 2SF 2 :CALEDONIAN HOTEL:PRINCES STREET:EDINBURGH:EH1 3AB 3 :GEORGE HOTEL:GEORGE STREET:EDINBURGH:EH2 1CD etc. |
