Tech Tip: Exporting ESRI .SHP Format Files

Manifold uses a standalone program, the Manifold Exporter, to export Manifold format files into ESRI shapefile format, AutoCAD DXF, and MapInfo MIF/MID format.  The Exporter installs as part of the 4.50 installation. Make sure you install the latest Service Pack to 4.50.

ESRI shapefiles use DBF format, a relic of dBase II days.  DBF format is more limited in many key aspects than Microsoft's MDB format used by Manifold.  In particular, DBF field names are limited to 8 characters and cannot contain spaces or other special characters.  This may pose a problem when trying to export Manifold maps that were created using "rich" field names, for example as a result of importing map data from "rich" data sources such as TIGER/Line.

TIGER/Line uses long, complex, descriptive field names that include characters such as the space character in the field name. An example is "FIPS 55 Code (MCD/CCD), 1990 Left".  In Manifold or Microsoft databases such as Access, one can use field names (ie, the column heads) that include spaces. For example, the "FIPS 55 ..." name is a legal field/column name in Manifold, Access and many other databases, but not in dBaseII (ie, DBF) or ESRI shapefiles.

When converting data from one format to another, one always has the problem of conversion to a format that supports fewer features or less data. In this case, both Manifold and TIGER/Line support a richer information set (ie, the richer field names) than ESRI SHP can handle. This means some of that information will be lost when exporting to SHP.

Manifold Exporter includes a "Short Names" button to automatically truncate filenames to 5 to 8 characters.  The latest version of the Exporter will chop field names down and will map characters that DBF does not understand, like spaces, into underscores.  It will also resolve conflicts that lead to identical names in the first few characters when longer names are chopped down to 5 or 8 characters.

Alternate Workaround: If you do not like what the automatic truncator does, you should change the field names so that the first eight characters do not include spaces or other "DBF illegal" characters, and then truncate to short file names.  This is best done at the time the initial map is created.  However, if the initial map is automatically created by importing from a "rich" data source such as TIGER/Line, the "rich" field names will be already defined.   Therefore, they must be changed manually.

Example: change "FIPS 55 Code (MCD/CCD), 1990 Left" to "FIPSmcL".

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