Life Cycle of Control Point Positions:
A Case Study Using a Multi-State Control
Point Database (MCPD)
Kazi Arifuzzaman and Keith T. Weber
Abstract
The life-cycle (usability) of a control point’s position is tied
closely to the control point’s stability, its datum, and velocity
changes across a region due to crustal movement. Analyses of
the coordinates of numerous control points stored in the Ida-
ho and Montana Multi-State Control Point Database (
MCPD
)
showed no statistical differences due to a point’s stability and
its physical setting. However, analyses comparing various
realizations of horizontal datum revealed some significant
differences. Specifically, there is >1 m difference observed
between coordinates using
NAD
83(1986) relative to
NAD
83(2011) and approximately 2 cm difference between
NAD
83(CORS96) and
NAD
83(2011) coordinates. A comparison of
vertical coordinates derived from geoid models revealed a 30
cm mean difference between
GEOID
03 and
GEOID
12A, and >60
cm difference between
GEOID
99 and
GEOID
12A. The impact of
velocity on these coordinates was apparent and varies strong-
ly with local tectonics across the eastern Idaho study area.
This study supports the
NGS
recommendation to use the most
current realization of horizontal and vertical datum available.
Introduction
In 2011, Geodetic Working Groups in both Idaho and Mon-
tana created the multi-state control point database (
MCPD
) to
share geodetic control point data. While frequently collected
for only a single project, control point data has many uses for
other projects and purposes (Pitzer, 2012). The control points
(
n
= 13,000) currently contained in the
MCPD
were submitted
by professional land surveyors in Idaho and Montana with
over 8,000 control points found in Idaho alone with more be-
ing added each month.
The significance of
MCPD
control points is manifold. The
MCPD
acts as a repository of control points, and disseminates
these data over the web
(
-
ers/mcpd/
). These data are valuable as many existing pas-
sive markers (e.g., monuments and benchmarks) have been
destroyed over time, or are scarce across the western US.
Active markers (e.g., Continuously Operating Reference Sta-
tions (
CORS
)) are too few to provide adequate control for many
local geospatial analyses. While the geospatial community
may be aware of spatial data quality issues, they may not have
at their disposal techniques and tools to determine quality (Li
et al.
, 2012). These concerns make the situation particularly
acute for today’s geographic information world and the
MCPD
provides a resource to resolve or address at least some of
these issues for Idaho and Montana. For example, the use of
passive, visible controls referenced through the
MCPD
would
improve the quality of orthorectification of aerial imagery
across Idaho’s rough terrain.
Many control points in the
MCPD
are right-of-way corners
or cadastral controls. Right-of-way corner controls define
highway, road, and street alignments and are usually set by
transportation departments (e.g., Idaho Transportation Depart-
ment (
ITD
)). Cadastral controls define property boundaries set
for the Public Lands Survey System (
PLSS
) by private survey-
ors. The monuments which represent a section corner were
originally set by surveyors from the General Land Office (
GLO
)
and, over time, either government or private surveyors have
perpetuated many of these monuments. Examples of monu-
ment types are brass caps, brass plugs, marked stones, iron
pipes, concrete posts, reinforcing bars with plastic or alumi-
num caps, and holes drilled in rocks. According to National
Geodetic Survey (
NGS
) criteria, these kinds of monuments are
considered stability category C or D. Stability is defined as the
monument’s ability to maintain a long-term, constant position
relative to other local features. Stability category C indicates
the position may hold well, but are commonly subject to
movement, whereas stability D may show unknown reliability
over time (Mark Stability,
NGS
).
The geodetic datums used to determine the horizontal and
vertical coordinates of control points are stored in the
MCPD
database and are not consistent across the
MCPD
. While the
North American Datum of 1927 (
NAD 27
) was not used, vari-
ous realizations of North American Datum of 1983 (
NAD 83
)
were used as a collection method of horizontal coordinates.
The successive
NAD 83
realizations are
NAD 83
(1986),
NAD
83
(
HARN
),
NAD 83
(
CORS96
),
NAD 83
(
NSRS2007
) and
NAD 83
(2011).
The latest vertical datum is
NAVD 88
for the conterminous US,
and surveyors report vertical coordinates in
NAVD
88. They
also report the geoid model used to realize
NAVD 88
vertical
coordinates and these data are part of the
MCPD
. During Global
Positioning System (
GPS
) surveys, a hybrid geoid model is
used to convert
NAD 83
ellipsoid heights into
NAVD 88
heights.
The first realization of
NAD 83
(1986) employed the Geodetic
Reference System of 1980 (
GRS 80
) as its reference ellipsoid
to compute position coordinates of the monuments obtained
by a triangulation network (Snay and Soler, 2000a).
NAD 83
is
a modern geocentric reference frame, commensurate with a
Conventional Terrestrial Reference Frame (
CTRF
) such as the
International Terrestrial Reference Frame (
ITRF
), World Geo-
detic System of 1984 (
WGS 84
) and International
GNSS
Service
(IGS) frame, and
GRS
80 entirely different from its predecessor,
Clarke 1866 (a local geometric ellipsoid which was oriented
based on celestial observations, and used for position deter-
mination in the triangulation network in
NAD 27
). With the
advancement of
GPS
, positioning accuracy became higher
than the 1
st
order accuracy obtained by older triangulation
GIS Training and Research Center, Idaho State University, 921 S.
8
th
Ave., Stop 8104, Pocatello ID 83209-8104 (
Photogrammetric Engineering & Remote Sensing
Vol. 84, No. 4, April 2018, pp. 215–225.
0099-1112/17/215–225
© 2018 American Society for Photogrammetry
and Remote Sensing
doi: 10.14358/PERS.84.4.215
PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING
April 2018
215
