Trusting GPS??

big rockpile · #1 08/22/06, 11:17 AM

Ok I know not Legal.But my property hasn't been Legally Surveyed,but one corner has been marked by a Surveyor.

Years ago I measured with a Compass and Tape,thought I was off one corner by 8 foot.Well when the Surveyor marked that one corner,I remeasured and came up I was right on.

Ok I got a New GPS went out to the Marked Corner,went to my other corner,should be 440 yards,GPS is showing 435 yards.Which would put my Line 5 yards futher.So I should be very good.

Like my wife says I should not worry so much,if someone wants to have it surveyed let them that we should be ok.

What you Guys think? Oh if I wanted to it will cost $2,000 to have it Surveyed.

big rockpile

simon66 · #2 08/22/06, 12:42 PM

Don't get to comfortable with your GPS reading...5 yards is within the expected error of the system, I believe. Are you planning to build on the line or close to it? If it was me, I wouldn't sweat it.

Scott

texican · #3 08/22/06, 12:47 PM

I wouldn't trust gps with just 'one read'... now if you take many many readings, and average them out, you'd get closer to the true mark.

VApigLover · #4 08/22/06, 02:39 PM

Your GPS should also (on the status page) provide how much error it estimates. On not so good days or selected availability (SA, not so sure they do that any more) your reading could be off as much as 120 feet. On good days some of those things are not much more accurate than 30 feet at best from a lat/long point. How that translates from point A to B don't know, you might be better off borrowing a hunting buddies range finder, some of those new ones are spot on!

pcdreams · #5 08/22/06, 02:48 PM

from what I understand (talking with IT folks who use these and should know) these things typically have error ratio as little as 1 meter or as much as 30.. Depends on how old the unit is,who manufactured it, if you're holding your mouth right, or many other obscure factors.

I wouldn't trust it but then again I'd be likely to agree with the wife.. Let someone else survey it. That said; most surveyors use them now.. Granted they're probally 100x better than what joe blow can get at bass pro or wally world.

ace admirer · #6 08/22/06, 04:08 PM

if YOUR prop has not been surveyed,,,has your neighbors been surveyed? if so,,,,that may be THE survey.

cavscout · #7 08/22/06, 04:28 PM

with one gps its reading is +or- 10meters no matter what it says. i went through a training program with the civilans that fielded the gps for the military. that is what they told us in the class about how they work. that is the reason we don't set mine fields with them. some of our equipment can get withing a meter but they have 2 gps built in to be able to get that accurate.

big rockpile · #8 08/22/06, 05:12 PM

Well mine says it can be off 3 Meters.I checked all corners coming off the Surveyors Marker.What I came up with is very close to what I came up with Compass and Tape.So I'm going to call it good.

A Range Finder won't work because you need a Clear View of Corners.

big rockpile

jehehmeyer · #9 08/22/06, 08:17 PM

I'd go along with your wife. Live is easier that way. LOL. Unless your putting up a fence, or a building close to the property line, what does it matter? Do you need to challenge the neighbors over their fence. If it is just idle curiosity, I'd let it go. The surveyor that put down the corner was probably right.

Jim

lwj2 · #10 08/31/06, 09:53 PM

That's within the error range of a non-milspec GPS. If you want more accuracy, you'll have to go milspec, which is likely to be hard to come by and expensive if available.

You may be able to rent a transit, or you can buy a used one.

Quote:

Originally Posted by big rockpile

Ok I got a New GPS went out to the Marked Corner,went to my other corner,should be 440 yards,GPS is showing 435 yards.Which would put my Line 5 yards futher.So I should be very good.

hillsidedigger · #11 10/15/06, 10:56 AM

How do you know the 440 yard distance in your deed is the correct distance? Most modern accurate surveys all over the U.S. reflect distances mostly expressed in feet and decimals of a foot (occasionally in meters), so a distance expressed in yards is very suspect to me.

All distances, bearings, angles and areas listed in descriptions are subject to error, maybe more, maybe less, some grossly more or less.

The practice of surveying involves an examination of 'the rules of evidence' to arrive at a correct conclusion. Surveying is not necassarily a black and white science (due more than anything to poor surveying procedures in the past) and surveyors due to their education, experience and tendency to acquire and learn how to use expensive equipment to measure distances and angles plus obtain the computers and software to crunch all the numbers and have learned to interpret old descriptions and so if qualified may be granted a license by the states to judge these 'rules of evidence'.

Many surveyors in the wide open parts of the U.S. now use GPS

but many surveyors in the forested, heavy canopy areas of the eastern U.S. find GPS to be of little value, except for possibly establishing a few points in open sky spots to control their conventional random traverses which are generally conducted with an electronic total station.

big rockpile · #12 10/15/06, 04:32 PM

Quote:

Originally Posted by hillsidedigger

How do you know the 440 yard distance in your deed is the correct distance? Most modern accurate surveys all over the U.S. reflect distances mostly expressed in feet and decimals of a foot (occasionally in meters), so a distance expressed in yards is very suspect to me.

All distances, bearings, angles and areas listed in descriptions are subject to error, maybe more, maybe less, some grossly more or less.

The practice of surveying involves an examination of 'the rules of evidence' to arrive at a correct conclusion. Surveying is not necassarily a black and white science (due more than anything to poor surveying procedures in the past) and surveyors due to their education, experience and tendency to acquire and learn how to use expensive equipment to measure distances and angles plus obtain the computers and software to crunch all the numbers and have learned to interpret old descriptions and so if qualified may be granted a license by the states to judge these 'rules of evidence'.

Many surveyors in the wide open parts of the U.S. now use GPS

but many surveyors in the forested, heavy canopy areas of the eastern U.S. find GPS to be of little value, except for possibly establishing a few points in open sky spots to control their conventional random traverses which are generally conducted with an electronic total station.

My Deed reads in Feet but my GPS reads in yards which is no big deal.

Deed reads 660 feet X 1320 feet,which is 220 yards X 440 yards.

The Surveyors in our area use GPS.Just they are better at getting such and such point to start with.Me I'm just going with one corner they have already Legally Marked.Go with it 440 yards True North,mark that coner,go 220 yards East,mark that,go 440 yards South,mark that corner,then if I go 220 yards West I should be at the starting corner.With 7 Satellites picking me up should be pretty dang close.

big rockpile

APPway · #13 10/15/06, 04:59 PM

we just did our land with a gps
We did it 5 times and also used 2 different ones and it came out the same 4 times and the other 2 times it was off by about 3 feet
Thats what they said we had on the purchase agreement and that is what we have,

bhowle · #14 10/15/06, 05:34 PM

I'm using my GPS receiver to find the 'fourth' corner of our new land. I've got three corners located, the fourth corner is somewhere beyond the bottom of a 30 foot limestone bluff - there should be a survey pin there somewhere near an old fence line.
The missing survey pin is probably covered with leaves so I'll nee to bring a small rake with me on my next trip down the bluff. Believe me, I'm gonna mark that pin with survey tape once I find it.

-bob

hillsidedigger · #15 10/15/06, 05:50 PM

Bigrockpile

The description of your property sounds like the east half or the west half of a quarter of a section (sections are supposedly square miles or 5280' X 5280' (invariably somewhat or maybe considerably different distances in reality) laid out in cardinal directions, subject to being very more or less cardinal directions)), sections are to be perpetuated as they were originally laid out 150 to 200 years ago, in many cases laid out very inaccurately and as such is termed an aliquot description.

The correct procedure to mark any corners that are not found in aliquot descriptions involves considering the entire section and then breaking it down by established proportionment procedures.

You might luckily, by assuming 660' X 1320' in cardinal directions and working from one known corner, get within a few yards of the other corners or you might be many dozens of yards from the correct positions of the unfound corners. Satellites were likely not used to originally lay out your parcel and so are not so relevent in attempting to retrace your lines.

In appway's case, the corners must have all been found marked?

Measuring between found corners is much simpler than measuring to an unknown corner.