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What is a GPS CORS?


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I use (now retired) to use these a lot in our Surveys. We would set up our 3 GPS receivers to run for 5.5 hours collecting data. Then send the data to OPUS and get back state plan coordinates on our survey points.


This example is a little jumbled up do to formating that does not work in this page. I can't get the font to print right so the data is more legible???




Subject: OPUS solution : 22011830.02o

Date: Tuesday, July 23, 2002 8:50 PM





USER: mraff@chartermi.net DATE: July 24, 2002

RINEX FILE: 22011830.02o TIME: 00:50:14 UTC


SOFTWARE: page5 0203.19 ./master.pl START: 2002/07/02 11:39:00

EPHEMERIS: igs11732.eph [precise] STOP: 2002/07/02 17:48:00

NAV FILE: brdc1830.02n OBS USED: 10574 / 11285 : 94%

ANT NAME: LEIAT502 # FIXED AMB: 117 / 130 : 90%

ARP HEIGHT: 1.629 OVERALL RMS: 0.025(m)


REF FRAME: NAD83(CORS96)(EPOCH:2002.0000) ITRF00 (EPOCH:2002.5003)


X: 159300.868(m) 0.021(m) 159300.230(m) 0.023(m)

Y: -4451619.426(m) 0.046(m) -4451618.095(m) 0.047(m)

Z: 4550009.296(m) 0.039(m) 4550009.246(m) 0.039(m)


LAT: 45 48 0.94203 0.008(m) 45 48 0.97232 0.009(m)

E LON: 272 2 58.02238 0.020(m) 272 2 57.99507 0.031(m)

W LON: 87 57 1.97762 0.020(m) 87 57 2.00493 0.031(m)

EL HGT: 295.048(m) 0.060(m) 294.068(m) 0.061(m)

ORTHO HGT: 329.507(m) 0.065(m) [Geoid99 NAVD88]


UTM: Zone 16

NORTHING: 5072294.885(m)

EASTING: 426132.463(m)


SPC: Zone 2111(MI)

NORTHING: 113469.186(m)

EASTING: 7926109.134(m)




AF9550 kew1 UPPER KEWEENAW 1 CORS ARP N471337 W0883727 166820

AF9553 stb1 STURGEON BAY 1 CORS ARP N444743 W0871851 122314

AJ5569 sup2 ESCANABA CORS ARP N454458 W0870424 68449



AA5210 22203 N454820 W0875932 3287


This position was computed without any knowledge by the National Geodetic

Survey regarding the equipment or field operating procedures used.


[This message was edited by elcamino on December 13, 2002 at 06:28 PM.]

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You would be looking for an antenna, about the size of the proverbial bread box, usually in a dome shaped or cone shaped housing to protect it from the elements, typically mounted on a high building with 360 degree visibility, often in a secure area, such as an airport, easy to spot from a distance, but for obvious reasons difficult to get close to. There are currently about 2 dozen in your state of Texas.

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The photo depicts the site of the CORS WIL1 antenna (which I wasn't able to get a good photo of). It appears to be located atop the Hayfield House on the PSU Wilkes-Barre branch campus at Lehman, PA. Certainly nothing exciting to see. I've got to return here in order to log the two other reference marks that are part of this station. I wasn't aware of them during my first visit. I hope to get better photos next time.


Happy trails ...


~Rich in NEPA~




=== A man with a GPS receiver knows where he is; a man with two GPS receivers is never sure. ===


[This message was edited by Rich in NEPA on December 14, 2002 at 07:21 AM.]

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One of the Continuously Operating Reference stations which forms part of the Australian Regional Geodetic Network. This is just the station mark/antenna. Most of these sites are secure and really not the type of thing one really should be playing with.


icon_smile.gif everybody keeps telling me where to go icon_wink.gif

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I sort of had an idea what GPS CORS is, I just had no idea what I might be looking for. AF9536 is not in a particularly secure area - it's a Department of Motor Vehicles office, where people go to get title transfers, etc. I guess the coords should be pretty exact, so whatever it is shouldn't be too hard to find. There are a bunch of other benchmarks on the grounds.



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That's pretty cool.

I noticed that I have a CORS station very close to me. I was thinking about going out to take a look at it, but it's at the FAA regional traffic center, a very secure site. They control all of the air traffic into the crowded San Francisco, Oakland, San Jose area.

Standing outside of the barbed wire fence with a pair of binoculars would probably look very suspicious.

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Went to Chatham, MA CG station today to see if I could see the CORS today. I stumbled onto the CORS site last night, and since I was headed that way, went for a look. Met a Coastie leaving the gate (closed since the 9/11 bit), and he was cool enough to point it out to me and give a fast tour of the station. I should have looked up the neares benchmarks, there are a slew of them in the area. Even though I saw a few (lighthouse,cupola, etc.) I won't claim them because I wasn't really looking for them. But as soon as it gets warmer and drier (August? icon_rolleyes.gif ) I'll go back and check out the rest around town and beef up this account with some finds. Curious to see what a 'tidal' marker may look like.

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(amature warning, I don't do this professionally.)


CORS is related to dgps, but is not necesarily directly related. As noted near the top of the thread, a CORS continusously collects GPS information, at a fixed and well known location (at least amoung the users of the CORS data).


An example of a non surveying use would be providing navigation information around a small harbor. Prior to GPS being widely available most well traveled waterways were covered by a fixed location broadcasting system called LORAN. There would be several LORAN transmiters along the coast. A CORS station could (and very well may have) provide supplemental data to LORAN receivers to compensate for whatever inaccuracy was built into LORAN.


Another use of CORS is to provide a DGPS and possibly WAAS alternative for people with low end computer connected GPSr. If the software you use supports it, the software can pull down correction data from a CORS, and get a more accurate fix on your current location.


Of course by the time you add up the cost of the computer, the cellular packet bills and modem cost, and the GPSr you have attached to the computer, you could probably pay for a much higher grade GPSr which supports WAAS or even DGPS. But of course the computer is usefull for other activities, which the higher end GPSr may not be. (like word processing and providing updates to the geocaching website.)


I strongly suspect that some (though not all) of the CORS marks are providing the correction information that WAAS enabled GPSr are using to bring the accuracy of such devices from 120 meters down to 15 feet.


Then again that's just my feel for the situation. I have been known to be wrong in the past.



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No CORS (or equiv) don't really have a direct/continuous relationship to dGPS sites but depending on how the reference sites were fixed CORS could have been used to initially do that.


CORS sites and data generally are higher up the tree then dGPS sites and within CORS (type) sites there's basically different hierarchical levels.


Cheers, Kerry.


I never get lost icon_smile.gif everybody keeps telling me where to go icon_wink.gif

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The basic difference is what they do.


DGPS broadcasts GPS corrections to GPS user (Marine mainly) because is a fixed location where high accuracy is not required. You have a GPS receiver with a DGSP radio receiver. You GPS tracks your position, you also receive the broadcast from the DGPS and it adds the correction to your receiver and more accurate locates your position. In the surveying field we call this RTK (real time kinematic). Most DGPS receivers need only accurate to 5 meters or so although there are highly accurate DGPS receivers but very costly. Also there needs to be a DGPS signal for you to use it, you can go out of radio range.


CORS on the other hand collects high accuracy GPS data 24/7, downloads it to a computer which them makes it available for downloading. The equipment you would need to use CORS is very costly ($1000's) related to what you would need ($100's) to use DGPS. CORS is used in the Surveying and other technical profession.


A CORS can also be a DGPS if configured to be(although not many are) but it requires more equipment but a DGPS will not be a CORS mainly due to cost.


FYI-To set up a CORS station would cost about $35,000 +/-. + a dedicate T-1 phone line, servers and software and the position has to be surveyed for 15 hrs, either continously of in 5.5 hr segments. It has to be precisely positioned to sub-centimeter accuracy and it constantly monitored by computer software to any positional movement.


CORS = Very high accuracy surveying

DGSP = Marine Navigation mainly


[This message was edited by elcamino on April 26, 2003 at 05:30 AM.]

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I am in wyoming and see they list one for ammoth hotsprings whihc is in yellowsotne park. can some one go to the tyomign lsiting and se hwo to read it so I can go look for it they have nophot so I want to take one for them. Mamoth hotsprings is a big area.

Originally posted by Web-ling:

What is this? http://www.geocaching.com/mark/details.asp?PID=AF9536


What would I be looking for?





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Unfortunately there isn't a picture of your CORS in the database http://www.ngs.noaa.gov/CORS/Data.html


Here's a picture of the CORS station in Mount Vernon, Knox County, Ohio



Originally posted by Web-ling:

What is this? http://www.geocaching.com/mark/details.asp?PID=AF9536


What would I be looking for?







"It's what you learn after you know it all, that counts."

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If the consideration is that DGPS is the Coast Guards safe navigation system, then there is indeed a direct link between DGPS and CORS. All of the Coast Guards DGPS sites are also listed in the NGS National CORS Network. All of these stations have redundant dual-frequency GPS units. The program called DGPS by the Coast Guard broadcasts corrects to improve real-time navigation (Marine) to the 1-3 meter level. The Coast Guard has no interest in distributing GPS carrier phase data to the surveying and mapping public. NGS has worked with Coast Guard since the inception of the program to obtain that carrier phase data and make it available to anyone who wants to do precise positioning. So the same stations serve the dual purpose of broadcast an improved navigation signal, and providing high quality carrier phase data for distribution by NGS. The same is ture for the FAA's Wide Area Augmentation System (WAAS). NGS assists both Coast Guard and FAA by insuring the quality and stability of the published positions of their broadcast sites at the +/- 1-2 cm level by using them in CORS

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Here's a photo (taken at dusk) of the USCG site at KEW1 & KEW2. The big antenna which you can't see the top is the broadcast for DGPS I think, although there does not appear to be anything on top of it.


btw-This is on Lake Superior shoreline which you can see a little of between the big antenna and the GPS antenna on the right.



[This message was edited by elcamino on June 17, 2003 at 10:05 AM.]

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