OT: GPS unit for survey



Do it right. Get a registered land surveyor in with his megabuck "total station" to do the real survey, then just use a garmin or whatever handheld to rough out your plan. Stake it out and call the surveyor back to tie it all in.
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clare at snyder.on.ca wrote:

I just want a GPS for roughing it out, I will certainly hire a surveyor when we decide where the lines should go.
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Related question:
How accurate is the compass function on "cheap" GPS?
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wrote:

+- 2 deg or so, pretty accurate. About the same as my old $30 Silva Recon compass. Enough to get within 5' or so in a 1/2 mile. A cheap GPS is $350 new.
ED
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Check your math! 2 in 1/2 mile gives an error of approximately 92 feet. 2 is saying that the desired point is within a 4 range. That would approximately 184 feet in a half a mile. Hire a surveyor.
Ivan Vegvary
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wrote:

You need to use one first before you pass judgement, If you take the shots in short lengths and back shoot to check for error. The accuracy is up to the operator---like a machine tool. I stand by my statements been there done that. Ask any timber cruiser, mine engineer ect...I do a bit of real estate work and check property line with surveys ect. and find a Silva Pathfinder to be as acccurate as a Garmin E trex and I usually get within 4-6 @ 1/2 mile of know points---on a good day without a lot of terrain ect. for recon purposes
I was refering to a *recon* survey and also recommended he hire a pro--diy survey is like a diy root canal...asking for trouble. Read the language used on FS easement that cover the surveyors ass---something like any errors found in the future stand as the easement..
ED
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wrote:

In the early 1950's, my father was involved in the staking of mining claims during the uranium rush in mid central Ontario. His favourite story involved the staking of an area which had been in the path of a tornado some seven years previous. Imagine pacing a compass line while crawling over tangled swamp timber some twenty or so feet above ground. Gerry :-)} London, Canada
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On Sun, 26 Nov 2006 19:00:18 -0500, Gerald Miller

Thats a good story, blowdown timber and rockslides are easy to break a leg on. Phelps Dodge has agents working overtime in this area--I wonder what they know.. Haven't seen them but have found a couple of new claim tags. Rumor has it they're claiming over anyone who hasn't kept proved up. Maybe a new metals rush?.
ED
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One degree error at one-half mile is about 40 feet.
John Martin
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wrote:

Get a Garmin E-Trx Summit. It has a flux-gate type compas and aneroid barometer built in. The compass is very accurate when standing still. GPS direction finding only works when in motion.
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clare, at, snyder.on.ca wrote:

Any magnetic field sensing device is effected by deviation and variation in the earth's magnetic field. I dont remember which is which but the one is an error caused by the north pole not being at the same place as the magnetic north pole. The other is caused by local magnetic material in the area. For example the border between NY and NJ is an slight arc but was supposed to be a straight line. It was surveyed right after the end of the revolutionary war. The arc was caused by the magnetic deflection from the iron ore deposits in the area. A gps survey would not show a curved line.
John
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Thanks John. It's the absence of magnetic variation/deviation with GPS that is of interest.
Jordan
John wrote:

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I know that this is just me being macguyverly again, but did you know you can make a really good GPS unit out of weather balloon instrument packages? They use DGPS so you have to have an initial known location, but apparently they're pretty accurate. I used to have a website about it bookmarked but I can't seem to find it now, I'll google it later. The other thing is that if all you're after is a rough estimate, use the GPS in your cell phone. Almost all cell phones report it now, and many have APIs for it. Nextel offers an easy-to-use pay service that will cost you much less than a new GPS. Just my two bits. GCC
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clare, at, snyder.on.ca wrote:

On a gps, you can load a present position and go to another position and it will give you the exact angle.
John
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If your just shooting bearings from a monument, a sighting compass is more than accurate enough to *recon* it in $30 -$70 or so. A gps is pretty good for finding your truck in the dark coming in from the woods ..:-)

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And if you don't know the basis of bearings of the monuments you could be off by the magnetic variation from true north. Up to 17 depending what part of the country. Lots of error! Hire a surveyor.
Ivan Vegvary
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wrote:

Magnetic declination adjustable compass's are the standard. Use USGS topos to get the amount, it's posted there. Interestingly the newer maps have change over the past 20 years by 4 degrees in my area. The monuments I was refering to are the brass caps for quad points...or a reference to them if possible, It can get tricky on a correction line.
ED
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http://www.howstuffworks.com/gps.htm
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IIRC, you can do a rough survey but you'll have to pay a licensed surveyor for it to be legal. IOW, you won't be able to change the deed.
You should see if there a survey on file at the county court house. If you are lucky you can take it, a compass, a metal detector and a pace count and find the markers. Unless its been a LONG time between surveys the markers will be steel or iron bars driven in the ground. If its been a while you might be out of luck. A lot of those old ones used trees (324' from the triple red oak) and creeks <shudder>
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Excellent information.

No need to shudder over"bearing trees" I have a few on the mtn ranch. Put up by a USNF surveyer-- one is 60+ yrs old and refers to distance in chain and links. The paint is fading a bit on that one. We also have a quad point in the middle of a river with 2 bearing trees to reference it. Try shooting a line off that one in the spring during runnoff. There are bright yellow signs to mark these with coordinates scratched on. Simple but it works.
Out in the west ranches commonly trade hands and have never been surveyed...we know what we own....sometimes. In my state acerage of 160 acres or larger don't need a survey to be bought/sold.
ED

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