Geography Reference
In-Depth Information
Simplified example of a metes-and-bounds description.
From www.premierdata.com/literature/Intro Land Information.pdf . Adapted by permission of Premier Data.
State-Plane Coordinate System
The State-Plane Coordinate System (SPCS) is a system for specifying posi-
tions of geodetic stations and measuring location using plane rectangular
coordinates. This is a local coordinate system for each state which is legally
defined in federal and state law. This coordinate system divides all fifty
states of the United States, Puerto Rico, and the U.S. Virgin Islands into over
120 numbered sections, referred to as “zones.” Larger states generally have
multiple SPCS zones—for example, Minnesota has three and California has
six. Each zone has an assigned code number that defines the projection
parameters for the region. SPCS uses three projections, depending on the
orientation of the zone and the state. The Lambert conformal conic projec-
tion is used for areas with an east-west orientation. Areas with a north-
south orientation use a transverse Mercator projection. The area of the Alas-
kan panhandle uses an oblique Mercator projection.
The SPCS uses two datums, the North American Datum of 1927 and the
North American Datum of 1983 (NAD 1927 and NAD 1983, respectively)
based on different models of the earth's shape and size. NAD 1927 uses
Clarke's 1866 spheroid (equatorial radius 6,378,206, flattening 1/294.98);
NAD 1983 uses GRS 1980 (equatorial radius 6,378,137, flattening 1/298.26).
The differences between the datums' geoids are significant and lead to size-
able differences (up to several hundred meters) between locations recorded
using SPCS NAD 1927 and SPCS NAD 1983 (see Chapter 3). Since then,
numerous regional modifications have also been made. These changes
necessitate great care when working with geographic information from the
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