Shapefiles Guidelines and Restrictions

This topic applies to Touchstone 4.x and 5.0. For information about guidelines and restrictions for vector files in Touchstone 5.1, click here.

Before importing shapefiles, consider the following guidelines and restrictions:

•          The shapefile name must begin with an alphanumeric character and can contain only alphanumeric characters, underscores, and spaces. For example, Mall_T=0.06 is incorrect while Malla_T_006 is correct.

•          The shapefile should not use SQL reserved words as field names. For example the field names should not contain: "merge",  "load", "add", etc. Here is the full list of SQL reserved words: http://technet.microsoft.com/en-us/library/ms189822.aspx  

•          Verify that the projection of the shapefile is set to GCS_WGS_1984 and the datum to D_WGS_1984. The projection information is specified in the PRJ component. While the PRJ file is not a required component for the import process, AIR recommends that you always make sure that the shapefile's coordinate system is set to GCS_WGS_1984 and the datum to D_WGS_1984. If the PRJ file is missing or it is not in the same project workspace with the other component files, Touchstone assumes that the shapefile is using the GCS_WGS_1984 coordinate system. However, if the PRJ component is missing and the shapefile was projected or created in a coordinate system other than GCS_WGS_1984, the import will fail and the user will be unable to import the data.

•          Make sure that the shapefile is not a read-only file and that you have read and write access to the file. You must also have write access to the folder where the shapefile components are stored. If you need to import a read-only shapefile, you must first import it into ArcMap and then export it to a new shapefile, making sure that you select the correct coordinate system. (Refer to ArcMap documentation for instructions about using the software.)

•          Make sure that the shapefile does not include objects—points, polygons, or polylines—with NULL geometry. Such objects have rows in the attribute table, but their geometry is empty. In the attribute table, a length of "0" for an object indicates NULL geometry. While Touchstone can import a spatial data file containing objects with NULL geometry, it skips the records for those objects and will not include data for those objects in analyses.

•          Make sure that you do not import a feature class file (.GDB) instead of a shapefile. If the file you want to import is a feature class file, you must first import it into ArcMap and then export it to a shapefile.

•          Make sure that the shapefile does not contain overlapping polygons. While the overlapping does not hinder the import process, the exposure locations will not be correctly assigned, resulting in incorrect Geospatial Analysis results.

•          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 shapefile with a predefined legend, make sure that you select a Legend Field that has the same data type or a compatible data type, and that contains the same range of values as the field in the original file used to generate the predefined legend.

•       Be aware that importing a large number of data points or polylines takes significantly longer than importing polygons.

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

•       Merging or dissolving bordering polygons with the same attribute can also improve rendering and analysis performance.

•       If a shapefile is still too complex, subdivide the data into multiple shapefiles, or convert the data to CSV Grid format for import.

•       The type of peril in the UPX/CSV exposure files must match the type of peril specified during the spatial import process. If the perils do not match, the geospatial analysis will complete with exceptions—there will be no accumulations.