This Hydrology DLG attribute information includes multiple files. There is a DBF file (dBASE version III - dlghydro.dbf) and a Word file (dlghyupd.doc) both with attribute information concerning Hydrology, in addition to this readme file.

The DBF file was derived from several text files, as was the Word file; where information is duplicated in both files it will be identical. The Word file, however, contains more information than DBF file. This is due mostly to the nature of the data and a database. The DLG data when imported has major and minor codes (in some cases in the SDTS format DLG data it is called entity information), 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 original files documenting this data came from the U.S. Geologic Survey (USGS), as text files. There were two sets of files; the original documentation, and an updated version from 1995. The more recent documents are available on this site, in a zipped version. The files included here are a combination of the new and old files. The DBF file contains ONLY the current (new) attribute codes. The WP 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. With these two files you should be able to resolve conflicts over unclear codes.

In some cases the text description could be transformed into numerals; where this was fairly easy to do, such as the major code (feet, meters, etc) for water surface elevation, numerals were inserted into the DBF file. In all other 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 water surface elevation minor code; the possible water elevation values were too numerous to be inserted.

For the hydrography data, the dlghydro.dbf file fields are labeled major1, minor1, description, and sdtsdlg. These are the fields in the DLG data where the actual attributes are found.

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 hydrography 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.

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.

Last Modified January 04, 2001 07:23 AM