Vector Files — Guidelines and Restrictions

Projections

AIR has certified various projections as described in the Projections topic.

File Size

The following table summarizes file size restrictions:

File Naming Conventions

• The file name must begin with an alphanumeric character and can contain only alphanumeric characters, underscores, and spaces.

• The file should not use SQL reserved words as field names.

  Here is the full list of SQL reserved words: http://technet.microsoft.com/en-us/library/ms189822.aspx.

Geometry

• Touchstone does not support layers with mixed geometry types, for example, points, lines, and polygons in the same file. Make sure that the vector files that you are importing are compatible with the layer type; otherwise, Touchstone may produce an error about incompatible geometry types when you run the analysis.

• Touchstone supports the import of files with Z and M attributes, but does not use them in processing or visualization.

• Touchstone can import a spatial data file that contains objects with NULL geometry, but does not use those objects in processing or visualization.

• AIR Worldwide recommends that you do not import a vector that contains overlapping polygons. While the overlapping does not hinder the import process, the exposures will be assigned to the polygons with the lowest ID, and, therefore, may not reflect what you want to do.

Symbols

Touchstone saves layer legends after importing them so that they are available to you later, for example, when loading multiple tornado events. If you plan to import a file with a predefined legend, make sure that you select a legend type that has the same data type used to generate the predefined legend.

Performance Considerations

When importing polygons, vertices counts in the hundreds of thousands or less should not take an excessive amount of time. However, vertices counts and/or feature counts in the millions are too complex and the polygons must be simplified to reduce the number of vertices and improve performance.