This Transportation DLG attribute information includes multiple files, in both Dbase III (dbf) format and MS Word 5.1 (WP) format. They are listed below with brief descriptions.

dlgtrans.dbf - this file contains attribute codes for all the transportation items
dlgtrnrd.dbf - this file is a subset of 100trans.dbf, and contains only the road and trail codes; they are 170-179 in the major1 field.
dlgtrnrr.dbf - a subset containing the railroad codes; 180-189
dlgtrnmt.dbf - a subset containing the pipeline, transmission line, and miscellaneous codes; 190-199.
sdtstran.dbf - a file containing attribute codes for all transportation items, but only as it relates to SDTS format data.
dlgtrnupd.wp - a WP 5.1 table containing all the attribute information, with notes on the new and old codes.
rd.wp - DLG standards document from USGS on the roads and trails data in WP 5.1 format
rr.wp - DLG standards document from USGS on the railroad data in WP 5.1 format
mt.wp - DLG standards document from USGS on the pipeline, transmission line, and miscellaneous transportation data in MS Word 5.1 format

The DBF files were derived from several text files, as was the WP table file dlgtrnupd.wp; where information is duplicated in the files it will be identical. The WP file, however, contains more information than DBF files. This is due mostly to the nature of the data and a database. The DLG data when imported has major and minor codes (or possible entity codes for the SDTS format data), all classified as numerals. The text documentation had a mixture of text and numerals in the attribute code columns. This did not translate perfectly into a database format that could be used as a lookup table. In addition, the WP file was derived from text completed before the DLG data was translated into SDTS format. For any questions concerning differing codes, please check the SDTS documentation referenced in that section.

The documentation this data came from the U.S. Geologic Survey (USGS), as text files. There were two sets of files; the original data users guides, and an updated version of standards from 1995. The transportation portion of the most recent documents are the files rd.wp, rr.wp, and mt.wp listed above. The other files included here are a combination of the new and old files. The DBF file contains ONLY the current (new) attribute codes. The WP table file contains the current attribute data as well as notations on the older attribute codes. BE AWARE that DLG data on the WWW may be new or old vintage, and may have old as well as new coding. Using information from both types of files you should be able to resolve conflicts over unclear codes.

In most cases for the roads and trails data the text description in the major or minor fields cannot easily be transformed into numerals in a lookup table. In these cases a 999 (for major codes) or 9999 (for minor codes) has been inserted into the location in the file where the text values were. The original values have been moved to the BEGINNING of the description field, and placed in parens (). An example of where this was necessary can be found in the U.S. route number code (major code 173, minor code is the route number causing many possibilities).

The assumption has been made with these files that if you are importing the DLG data into ArcView or Arc/Info you will import the transportation information as a line file. The information displayed in the attribute files WILL be different if you import the files as a polygon for example. You may wish to perform different imports for display purposes but should import them as described above in order to use the DBF files as lookup tables for descriptions.

Of the transportation files, the roads and trails information was the least consistent in how the attribute information was organized. In the sample DLG format data used, there were up to 4 major and minor code sets. There was no intuitively obvious logic in how the attributes were coded; for example the major/minor combination 170/210 could be major/minor 1 or 2, 179/30 was found in major/minor 1, 2, or 3 etc. Because of this, creating a useable lookup table was challenging.

The tables dlgtrans.dbf and dlgtrnrd.dbf have a number of fields to allow several options in how to relate the tables to the DLG data files. The fields are Major1, Minor1, Major2, Minor2, Major3, Minor3, Description, MM1, MM2, and MM3. There were so few Major4 and Minor4 codes that that column was not included. The values are the same for each set of Major and Minor codes. The MM1, MM2, and MM3 columns are computed, each one being a sum; MM1 equals Major1 + Minor1, for example. Equivalent columns can be computed in the DLG data files, and some of the relates worked better using these computed columns rather than the original minor 1, 2, and 3 columns. For a specific example, see the suggestions for using the lookup tables in ArcView.

Major codes 172 - 176 were edited individually and the appropriate route numbers added when using the data. The lookup table has a 9999 value in the minor field. Problems with the data frequently involved the major code 179, which is no longer used by which exists in much of the older data. This code indicates coincident features; i.e. that the feature has more than one code.

This set of information was generally easy to use and consistent. The file dlgtrnrr.dbf includes only Major1, Minor1, Description and Sdtsdlg. Lookups can be done using Minor1 or Sdtsdlg.

Specific Pipeline, Transmission Line, and Miscellaneous Feature Information

As with the Railroad information, this set of data was generally easy to use and consistent. The file dlgtrnrr.dbf includes only Major1, Minor1, Description and Sdtsdlg fields. Lookups can be done on the Minor1 or Sdtsdlg fields.

SDTS Note: Getting attribute information into ArcView or Arc/Info from SDTS data is not a simple one-step process. The DBF file described here has a column labeled SDTSDLG the contains attribute codes derived from the Major/Minor columns in the original DLG format data. Use of this column will be clearer once you have stepped through converting SDTS data. It is included in this DBF file so that only one DBF file is needed for relating attributes for either DLG or SDTS format data.