DEPARTMENT OF THE ARMY
ETL 1110-1-183
U. S. Army Corps of Engineers
CECW-EP
Washington, D.C. 20314-1000
Technical Letter
No. 1110-1-183
1 April 1998
Engineering and Design
USING DIFFERENTIAL GPS POSITIONING FOR
ELEVATION DETERMINATION
1. Purpose
c. U.S. Army Corps of Engineers (1994),
Deformation Monitoring and Control Surveying.
This engineer technical letter provides technical guidance
Engineer Manual 1110-1-1004, U.S. Army Corps of
for using Differential Global Positioning System (DGPS)
Engineers, Washington, D.C.
to determine elevations of survey benchmarks for wide-
area mapping and GIS database development
d. U.S. Army Corps of Engineers (1996),
applications. Recommended procedural specifications for
NAVSTAR Global Positioning System Surveying.
field DGPS observation sessions are included.
Engineer Manual No. 1110-1-1003, U.S. Army Corps of
Engineers, Washington, D.C.
2. Applicability
e. Zilkoski, D.B., D'Onofrio, Joseph D., and
This letter is applicable to major subordinate commands,
Frankes, Stephen J. (1997) Guidelines for Establishing
districts, laboratories, and field operating activities
GPS-Derived Ellipsoid Heights (Standards: 2 cm and 5
having responsibility for civil works, military
cm), Version 4.1.1. Silver Spring, Maryland. NGS
construction, or environmental restoration projects.
Unpublished Report.
These DGPS guidelines and specifications are intended
for densifying vertical control over large project areas,
f. Zilkoski, D.B., Richards, J.H., and Young, G.M.
such as an entire military installation or watershed basin
(1992). Special Report: Results of the General
mapping project. The DGPS methods outlined in this
Adjustment of the North American Vertical Datum of
letter are generally not intended, nor would be cost-
1988, Silver Spring, Maryland.
effective, for small projects or any type of construction
lay out work where vertical grades or benchmarks require
4. Distribution
an accuracy better than 30 millimeters (mm). In such
cases, conventional differential leveling methods should
This information is approved for public release.
be used.
Distribution is unlimited.
3. References
5. Discussion
a. FGCC, (1991), Standards and Specifications for
a. Global Positioning System (GPS) surveying
Geodetic Control Networks, Silver Spring, Maryland.
produces a set of X-Y-Z coordinates which can be
(FGCC is currently known as FGCS)
transformed into geodetic latitude, longitude, and
ellipsoidal height by using an reference ellipsoid to model
b. Milbert, D.G. and Smith D.A. (1996).
the earth. In the U.S., most GPS ellipsoid heights are
Converting GPS Height into NAVD88 Elevation with the
measured with respect to North American Datum of 1983
Geoid96 Geoid Height Model. National Geodetic Survey,
(NAD83) control values, which are based on the Geodetic
Silver Spring, Maryland.
Reference System of 1980 (GRS80) ellipsoid. Published
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