OT: GPS unit for survey

I know about nothing about GPS units but would like to find something reasonable (on ebay?) to help survey a 100ac farm with an eye to subdividing it into 3 parcels (parents died). What kind of accuracy or repeatability should I hope for? Need accurate, durable, portable, cheap (i know, pick one ;) Recommendations for brands, models, prices appreciated from those with hands-on experience. TIA

Reply to
Nick Hull
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Nick,

A good consumer grade GPS in the $1000 range that has whats called WAAS will get you to about 3 meters of accuracy. With out WAAS you'll be in the couple of 100 feet.

I'm a Garmin kinda guy, I've have several of their products over the years and have been quite happy with them. I currently have a 296 that I fly with, it's not quit eop of the line but I don't care about XM radio/weather soo.. the 296 cost me $1200 A quick check on flea-bay shows 296's at $950 you probably don't need an aviation rated portable, since it comes with a bunch of data you don't need.

But with all that said you really should have a pro do this.. they use $$$ differntial GPS units and get down to centimeter accuracy...

--.- Dave

Reply to
Dave August

In our state you have to record the subdivision at the county recorders office before you sell. A surveyor does this as part of the survey. Otherwise, you have to hire a lawyer to draft the language. This actually costs more than the surveyor. So, save yourself time and money, just hire it done.

Karl

Reply to
Karl Townsend

IMO don't even think about it.....! Unless you like to spend your $ on lawyers.. To do a property line resurvey for a 1/4 section it cost me about 5k this fall. This is in the mtns and there were no monuments prior surveys, ect. You need some gee wiz gps gear for accurate survey work think $$$$, not the handheld stuff.

A handheld unit is only accurate to 15meters between data points , heck a hand held sighting compass can do 1- degrees if you know what you are doing. But you want something that's bullet proof, believe me....I know a guy who was recently told his newly built cabin need to be moved cuz it's on someone elses property...it's getting real me$$y.

If you insist on DIY get something like this:

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learn the basics and do it the old fashioned way. Just my .02 worth

ED

Reply to
ED

If you are in range of a WAAS signal you can get within about 5 or 10' of a specific spot on the earth. Without WAAS you can't rely on anything closer than maybe 30 to 60'. However, relative distance and bearing over a short period of time can be accurate within a couple of feet. For example to test the accuracy you could locate an established corner pin and set a waypoint. Then walk the bearing of the property line and when you reach the other corner pin and compare the GPS reading to the waypoint to the survey plat. I tried it with my 176C along my property line and it was within half a degree and 2 feet over 1400 feet. OTOH, it showed a USGS marker near the center of my property off by 16' one day and on the money the next. (No WAAS in my area.)

Most GPS units will tell you what their error is. Just checked mine against an old tree stump I can see on Google Earth. The GPS says it has a position error of 21' and Google Earth shows exactly the same thing. Walking 300' to the corner of the boat shed showed exactly the same error in distance and direction.

GPS will not give you a legal description but it will give you a good idea what the lots will look like.

Reply to
Glenn Ashmore

There is no way that any consumer grade GPS will give you the accuracy necessary for land transactions. I've been doing some GPS mapping of old trails and abandoned roads as well as some newly cut logging roads. Plain old Garmin GPS. I'm experiencing about 20' to 40' of random GPS error as well as about 50' of systematic error when I transpose this on to a map. My Garmin is fairly old, the new ones in my class run $100 to $200

BUT: If the land is hilly, irregular shape, trees, some good land, some low value land, etc, and you want to cut it into "reasonable" shapes rather than "accurate" shapes, a consumer grade GPS can be a big help. You would still need to have a surveyor do a certified (whatever that means in the jurisdiction the land is in) land survey

If this makes sense, get a Garm> I know about nothing about GPS units but would like to find something

Reply to
RoyJ

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.

Reply to
clare at snyder.on.ca

Here is one for $119.00. Claims 1 to 5 meter typical accuracy.

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Reply to
Ken Davey

I just want a GPS for roughing it out, I will certainly hire a surveyor when we decide where the lines should go.

Reply to
Nick Hull

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Reply to
mrbonaparte

Looks interesting but it appears to only have drivers for PCs and mt laptop is a Mac.

Reply to
Nick Hull

Related question:

How accurate is the compass function on "cheap" GPS?

Reply to
Jordan

Chuckle - score one for Micro$oft. -- Regards. Ken.

Please join my team in the fight against cancer.

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Reply to
Ken Davey

+- 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

Reply to
ED

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 ..:-)

Reply to
ED

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

Reply to
no spam

Select a model that is WAAS-enabled, can take an external antenna, and has a PC interface. Garmin models 60 and 76 are around $200 plus or minus. Magellan probably has comparable models.

The external antenna can sometimes significantly improve accuracy because it grabs more signal and sometimes enables the unit to pick satellites with better geometric spread -- i.e., further apart in the constellation. This often means at lower angles with weaker signals. It may also, in some locations, enable use of WAAS signals that are too weak to grab without the higher-gain antenna.

Under good conditions, accuracy can be 3 to 7 meters: not nearly good enough for surveying, but certainly useful for approximate mapping.

Magellan Promark 3 can provide survey-grade accuracy for about $3K.

Reply to
Don Foreman

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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Reply to
ED

Hire a legal surveyor for subdivision purposes. They have GPS based equipment that is actually accurate.

Even the really good consumer models available have a resolution of a couple yards in general, which is OK for finding a spot that you know the coordinates of, but not much to base a legal lot description on. Not around here, anyway.

A short chat with the lawyer that is handling the subdivision legalities should sort that out.

For just doing the rough survey for the lots, the survey map from your county, and Google Earth, if it has decent resolution of your area, are about all you need to lay out for.

No point in humping all over the 100 acres, and then having to pay someone else to do it.

Last time I went looking for iron pins in the bush (Vancouver Island, northern tropical rainforest kinda bush) I used a known marker and spools of cord to get within a few feet of the markers I needed to find. Worked for me!

Cheers Trevor Jones

Reply to
Trevor Jones

No such luck, very old survey was done in rods, but it doesn't tell how many. At least the border lines are fences and well established.

Reply to
Nick Hull

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