# Accuracy assessment of the National Geodetic Survey’s OPUS-RS utility

14 pages

### Abstract

OPUS-RS is a rapid static form of the National Geodetic Survey’s On-line Positioning User Service (OPUS). Like OPUS, OPUS-RS accepts a user’s GPS tracking data and uses corresponding data from the U.S. Continuously Operating Reference Station (CORS) network to compute the 3-D positional coordinates of the user’s data-collection point called the rover. OPUS-RS uses a new processing engine, called RSGPS, which can generate coordinates with an accuracy of a few centimeters for data sets spanning as little as 15 min of time. OPUS-RS achieves such results by interpolating (or extrapolating) the atmospheric delays, measured at several CORS located within 250 km of the rover, to predict the atmospheric delays experienced at the rover. Consequently, standard errors of computed coordinates depend highly on the local geometry of the CORS network and on the distances between the rover and the local CORS. We introduce a unitless parameter called the interpolative dilution of precision (IDOP) to quantify the local geometry of the CORS network relative to the rover, and we quantify the standard errors of the coordinates, obtained via OPUS-RS, by using functions of the form $$\sigma ({\text{IDOP}},{\text{RMSD}}) = \sqrt {(\alpha \cdot {\text{IDOP}})^{2} + (\beta \cdot {\text{RMSD}})^{2} }$$ here α and β are empirically determined constants, and RMSD is the root-mean-square distance between the rover and the individual CORS involved in the OPUS-RS computations. We found that α = 6.7 ± 0.7 cm and β = 0.15 ± 0.03 ppm in the vertical dimension and α = 1.8 ± 0.2 cm and β = 0.05 ± 0.01 ppm in either the east–west or north–south dimension.

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### Article Details

Title
Accuracy assessment of the National Geodetic Survey’s OPUS-RS utility
Author(s)
Charles, Schwarz; Richard, Snay; Tomás, Soler
Journal
GPS Solutions , Volume 13 (2) Springer Journals – Mar 1, 2009
Publisher
Springer-Verlag
Copyright
Copyright © 2009 by Springer-Verlag
Subject
Earth Sciences; Electrical Engineering; Automotive Engineering; Extraterrestrial Physics, Space Sciences ; Meteorology/Climatology ; Geophysics/Geodesy
ISSN
1080-5370
eISSN
1521-1886
D.O.I.
10.1007/s10291-008-0105-0
Publisher site
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