River Mile System of Ohio
The river mile system is a method to reference locations on streams and rivers of Ohio. Discrete locations on a stream or river are referenced by river miles. River miles are a linear measure that begin at the mouth of a drainage, and increase in an upstream direction along its path.
History of the River Mile System
River mile measurements were hand-drawn on 7.5-minute USGS topographic maps between 1972 and 1975. Since the completion of the index, river mile measurements have been incorporated into the programs and activities of the Division of Surface Water. Many stream features, such as the location of wastewater discharges and water-quality assessment sites, are referenced using the river mile system. The paper river mile maps were scanned in 2006. The scanned images were saved in JPEG image format, and georeferenced using industry-standard GIS software.
Downloading Digital River Mile Maps
Georeferenced river mile maps are available for download from the Ohio EPA FTP site. The digital river mile maps can be viewed in any application that supports JPEG images; however, GIS software that recognizes a world file is required to display the maps in their correct spatial position.
There are 787 river mile maps. Each map is named according to the 7.5-minute USGS quadrangle to which it corresponds. River mile map indices are available to determine the maps needed for a particular area-of-interest. A river mile map index is available in shapefile format, and is downloadable below. GIS software is require to view the shapefile. If access to GIS software is not available, an index map for use as a general guide can also be downloaded below.
Spatial Reference Information
The digital river mile maps are georeferenced to the Ohio State Plane South coordinate system. The coordinate system units are feet. The datum is NAD 1983.
The river mile maps are not available for download with an auxiliary file (.aux). This is because of an issue with different versions of GIS software. If the maps are to display correctly in a GIS application, the coordinate system of the map must be set to Ohio State Plane South (feet). That is true regardless of the ability of an application to project on-the-fly.
FAQs
Q: Are ORSANCO "mile points" the same as "river miles"?
A: No, they are both systems of measurement along the Ohio River, but they are not identical. ORSANCO mile points increase in a downstream direction, while river miles increase in an upstream direction.