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Calibrate your GPS using state surveyor markers


Guest station27

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Guest station27

s unless you have a lot of time. It will return a list of PID's around the lat/log you entered. Highlight one or more and click GET DATASHEET for that PID. Note: a lot of the markers have been destroyed or are in inaccessable locations e.g. inside a military site or on private property. Good Luck! TOM

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Guest Forester

Careful when using these survey markers. Use only the most recent in your area. I have found that in some parts of the country the surveys are a bit "loose". I have found 3 seperate brass caps for the same section corner within 200' of each other.

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I found going to the NGS home page is better for me.

 

http://www.ngs.noaa.gov/datasheet.html

 

There you can select 7.5 quads or use min/max coordinates in case you interesteed in covering a larger geographic area and not repeat search areas which happens when you use the radius method. There's a link there to the USGS page that lets you find out any quad in the country - great for traveling also. Once you get the quad name you insert into the NGS search engine and you get all the markers in that quad. The you can move onto an adjacent quad, etc. Ditto for the min/max but don't make teh coordinates too big.

 

My cache site is a marker that won't move to easy. It's 7 1/2 foot diameter granite slab. http://www.geocaching.com/seek/cache_details.asp?ID=10814

 

Alan

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Guest rdwatson78

Make sure you know what kind of marker you are looking for. Most of the markers I have found are vertical control markers which are fine if you just want to check GPS elevation accuracy. The fine print of vertical marker datasheets says that the horizontal coordinates have been scaled from a topographical map and are accurate to within +/-6 seconds. To check horizontal accuracy you have to find a horizontal control marker (makes sense). BTW on a topo map, vertical markers will be shown as an X with the letters BM near it, horizontal controls are shown as a triangle.

 

I have found several markers in my area and submitted recoveries for them. I found a marker that had been reported missing in 1980 and another marker that had not been recovered since 1930. rdw

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Guest station27

The Data Sheets for a given location usually lists more than one, 3 typicially in California. In my case it was ROSE, ROSE-1 and ROSE-2 all withing 100ft of each other.

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