Mine Mapping and Surveying - Coal Waste Impoundments: Risks, Responses, and Alternatives - page 66

SIDEBAR 4.5 COORDINATE SYSTEMS
The most commonly used coordinate system today is latitude and
longitude, which are defined by reference planes based on the Prime
Meridian and the Equator (Snyder, 1987). Latitude is measured in
degrees north or south of the Equator, and longitude is measured in
degrees east or west of the Prime Meridian.
In the United States, the state plane system was developed to
provide local reference systems that were tied to a national datum. This
system divides the United States into more than 100 distinct grid zones
and provides an easily used, flat grid that maintains a difference between
geodetic and grid distance of 1:10,000 or better. The first state plane
system was developed in the 1930s and was based on the North
American Datum 1927 (NAD27) (in feet). This system has been largely
superseded by the North American Datum 1983 (NAD83) (in meters),
although maps in NAD27 coordinates are still in use.
Mine surveyors can also use a local system based on an on-site
monument. A grid is established based on direction and distance
measured from the monument. These coordinate systems, because they
do not take into account the curvature of the Earth, lose accuracy as the
grid is extended away from the base station. In addition, these systems
may be difficult to transform with other coordinate systems, especially if
the on-site monument is displaced or unmarked.
SOURCE: Dana, 1999.
the time and expense associated with a closed-loop survey to tie the mine
to a U.S. Geological Survey monument.
Where large mineral-holding companies control mineral rights,
considerable time and effort has often focused on establishing transformation
equations between local and state plane coordinates. The equation involves a
fixed rotation angle and lateral offset to convert from the local system to state
plane coordinates. However, in some instances a single, unique coordinate
transformation is not applicable to an entire property. Thus, conversion of a
particular mine map from local to state plane coordinates, requires knowledge
of the geographic limits of a particular coordinate transformation. The
committee recommends that appropriate coordinate transformation
equation(s) be listed on the mine map.
Where no coordinate transformation exists, extreme care must be used in
referencing maps from abandoned mines into state plane coordinates or latitude
and longitude. In these situations, the transformation may be based upon
aligning creeks, roads, or other planimetric features to establish the mine
location. However, the surveyor or engineer must recognize that the