shrug-l: FW: [Fwd: internet resource of the month]

Rosenfeld, Brian rosenfb@doacs.state.fl.us
Wed, 24 Mar 2004 14:06:20 -0500


If you're using GPS this may be of interest....


--------------------------------- Original Message
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Subject: internet resource of the month
From:    "Tom Colson" <
Date:    Wed, March 24, 2004 10:37 am
To:     =20
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http://www.ngs.noaa.gov/OPUS


The National Geodetic Survey (NGS) operates the Online Positioning User
Service
(OPUS) to provide Global Positioning System (GPS) users easier access to
the
National Spatial Reference System.

OPUS allows users to submit GPS data files to NGS, where the data will
be processed
to determine a position using NGS computers and software. Each data file
submitted
will be processed with respect to three Continuously Operating Reference
Station
(CORS) sites selected by distance, number of observations, site
stability, etc.
Positions for the data are reported back to users via e-mail in
International
Terrestrial Reference Frame (ITRF) and NAD83 coordinates as well as UTM,
USNG and
State Plane Coordinates (SPCs).

OPUS-derived positional coordinates are the average of three distinct
single-baseline solutions computed by double-differenced, carrier-phase
measurements
from three different national CORS sites. The reference ITRF coordinates
for CORS
were obtained from the NGS Integrated Data Base and are updated to the
midpoint of
the time interval when the submitted data were observed.

OPUS is automatic and requires only a minimal amount of information from
users:

1. The e-mail address where users want results sent.

2. The data file that users want to process (which can be selected using
the browse
feature).

3. The antenna type used to collect a data file (selected from a list of
calibrated
GPS antennas).

4. The height of the Antenna Reference Point above the monument or mark
users are
positioning.

5. As an option, users can enter the state-plane coordinate code if they
want SPC
northing and easting.

6. As an option, users can select up to three base stations to be used
in
determining a solution.

After the information is complete, users then click the Upload button to
send data
to NGS. The results will be e-mailed to users, usually within a few
minutes. They
may upload multiple data files in a ZIP archive, but the options that
users choose
will be applied to all data files in the archive.

According to the Web site, it's important that users understand how to
correctly
submit data and interpret results. An OPUS e-mail button is provided for
any
inquiries or comments. The site also includes a page showing new
solutions that have
been added.

OPUS is intended for use in the conterminous United States and most
territories.
NGS' policy is to not publish geodetic coordinates outside the United
States without
the agreement of the affected countries. gw




Thomas Colson, MCP, CCNA
Center For Earth Observation
College of Natural Resources
5111 Jordan Hall
Campus Box 7106
Raleigh, NC 27695