Mine Mapping and Surveying - Coal Waste Impoundments: Risks, Responses, and Alternatives - page 65

Coordinate Systems
At least two and preferably three reference points are established on the
surface, usually near the portal or shaft (30 C.F.R. § 75.1200-1 (h)) before an
underground mine is opened. These surface points are tied to a coordinate
system (latitude and longitude, state plane, or local) ( Sidebar 4.5 ), so as to
enable mine workings to be accurately located in the framework of surrounding
surface features. The surface points are a permanent reference that can be used
if the portal or shaft location has become obscured by collapse or post-mining
reclamation. Subsequent mine surveying and mapping is based upon a fixed
point within the mine, a point-of-beginning, that is referenced to the surface
points.
The majority of active underground mines use the state plane coordinate
system. The surface points are fixed surface monuments, tied to both the state
plane system and at least one point referenced to latitude and longitude. Using
state plane coordinates is advantageous because utilities (electric power lines,
gas transmission lines), roads (federal, state, and county), and other planimetric
features are typically referenced to the state plane system; and because U.S.
Geological Survey topographic maps list both North American Datum 27
latitude and longitude and state plane coordinates, so mines can be located
easily on commonly available maps.
The committee concludes that the variety of mapping and coordinate
systems in use at present increases the potential for misinterpretation or
inaccuracy in underground mine locations. Therefore, the committee
recommends that state plane coordinates or latitude and longitude and
bottom-of-seam elevations as the map base reference. However, when using
latitude and longitude, the mine operator should clearly designate whether the
mapping is based upon North American Datum 27 or North American Datum
83. Elevations of seam bottom, used to establish the vertical position of the
mine, must be referenced to mean sea level.
Unfortunately, no uniform standard sets an appropriate coordinate system
or the type and placement of surface reference points. The choice of a mine
coordinate system can vary with the age of the mine, the operating company,
the geographic location, or the mineral lessor. As expected, the largest variation
in practice occurs in older mines (pre-1969) and small mines. Historically, local
coordinate systems have been prevalent where a single entity owned the mineral
rights to large, contiguous tracts. Where this practice continues, it is limited to
specific properties controlled by mineral-holding companies. In these instances,
a coordinate transformation between the local and state plane coordinates is
given. Similarly, for small hilltop mines operating in remote areas, there was
little economic justification for