Digital Line Graphs (DLGs)

Background
A DLG is a vector file containing line data, such as boundaries, hydrography, public land survey system, roads, railroads, miscellaneous transportation, and hypsography.

The State of Ohio is covered by 793 7.5 minute quadrangles (1:24,000 Scale). Each quadrangle has seven layers: (1) Boundaries, (2) Hydrography, (3) Public Land Survey, (4) Roads and Trails, (5) Railroads, (6) Miscellaneous Transportation and (7) Hypsography (countours).

The DLGs in native format (optional) are stored in UTM coordinates, Zone 16 & 17, NAD 27. The DLGs meet national map accuracy standards for 1:24,000 scale.

Layer Definitions
Boundaries This category of data consists of (1) political boundaries that identify States, counties, cities, and other municipalities, and (2) administrative boundaries that identify areas such as National and State forests. Political and administrative boundaries are always collected as a single data set.
   
Hydrography This category of data is currently being collected as combined hydrography consisting of all flowing water, standing water, and wetlands.
   
Public Land Survey System (PLSS) This category of data describes the rectangular system of land surveys that is administered by the U.S. Bureau of Land Management. PLSS data are only collected for areas falling solely, or in part, within the States that were formed from the public domain. The PLSS subdivides the public domain and represents property boundaries or references to property boundaries. These DLG data are not intended to be official or authoritative. They are presented as cartographic reference information. The only legal basis for determining land boundaries remains the original survey.
   
Transportation This category of data includes major transportation systems collected in three separate overlays labeled:
(1) Roads and Trails,
(2) Railroads, and
(3) Pipelines, Transmission Lines, and Miscellaneous Transportation Features.
   
Hypsography This category of data consists of information on topographic relief (primarily contour data). 

 
Distribution & Format
The GIS Service Bureau distributes DLGs in native format only. To decrease file size and transfer time, the native DLG files have been individually compressed into a Zip format. The files can be decompressed with any software that handles Zip files like Unzip, PKUnzip, or WinZip to name a few.

Free software called dlgv32 can be used to view the native format DLGs.
 
Download
DLGs for the State of Ohio can be downloaded for free.

DLGs are also available from the United States Geological Survey (USGS).

Web Address:  http://gis3.oit.ohio.gov/geodatadownload/data.aspx