# Land Survey Accuracy **URL:** \ **Category:** Factual Questions\ **Created:** [August 23, 2005, 2:17pm UTC](https://boards.straightdope.com/t/land-survey-accuracy/318257 "2005-08-23T14:17:29Z")\ **Posts on this page:** 17\ **Page:** 1
**Author:** ![YPOD](https://avatars.discourse-cdn.com/v4/letter/y/e99b99/32.png) [@YPOD](https://boards.straightdope.com/u/YPOD)\ **Post date:** [August 23, 2005, 2:17pm UTC](https://boards.straightdope.com/t/land-survey-accuracy/318257/1 "2005-08-23T14:17:29Z")
We live in an old house (1850), as does our neighbor. I am in the process of getting my property surveyed and the guys just finished staking the property line between me and my neighbor, who appears to have built his deck and fence on our property (over our objections). The problem I have is that the surveyors placed the stakes about two to three feet from where the property line appears on the old survey (as measured from my house’s foundation). We have a copy of the last survey done before our previous neighbors moved out, which also indicates that the stakes are a little bit off. I do not yet have the final survey map from the survey company; they guys doing it simply said that I should wait for the final copy. How accurate are surveys today? Is it a matter of feet or inches? Do different surveys usually vary from each other? What do we do if the surveys differ from each other? ---
**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\ **Post date:** [August 23, 2005, 3:53pm UTC](https://boards.straightdope.com/t/land-survey-accuracy/318257/2 "2005-08-23T15:53:11Z")
Using GPS equipment in differential carrier phase measurement mode can get accuracies of millimeters. What your local justice of the peace is going to do with those data is another question. ---
**Author:** ![Shagnasty](https://avatars.discourse-cdn.com/v4/letter/s/9dc877/32.png) [@Shagnasty](https://boards.straightdope.com/u/Shagnasty)\ **Post date:** [August 23, 2005, 4:12pm UTC](https://boards.straightdope.com/t/land-survey-accuracy/318257/3 "2005-08-23T16:12:23Z")
> [@Napier](#): > > Using GPS equipment in differential carrier phase measurement mode can get accuracies of millimeters. What your local justice of the peace is going to do with those data is another question. That is something I always wondered. I can understand how modern technology can calculate locations down to the millimeter. However, how were the old boundaries originally set so that you can go back and mark them with such accuracy? My house was built in 1760. The land is marked by the stone walls that have since partially fallen or been moved a little. How does a surveyor know that the boundary falls in a given spot? ---
**Author:** ![butler1850](https://avatars.discourse-cdn.com/v4/letter/b/779978/32.png) [@butler1850](https://boards.straightdope.com/u/butler1850)\ **Post date:** [August 23, 2005, 4:20pm UTC](https://boards.straightdope.com/t/land-survey-accuracy/318257/4 "2005-08-23T16:20:43Z")
> [@Napier](#): > > Using GPS equipment in differential carrier phase measurement mode can get accuracies of millimeters. What your local justice of the peace is going to do with those data is another question. JP? I’d imagine (well, it was in MA) Land Court, or the local Zoning board, or building inspector, perhaps a clerk magistrate. My wife, a JP, certainly wouldn’t have anything to do with land disputes, notarization, marriage, and a few other things that require a witness, but I’d doubt land issues. Surveys using ancient landmarks can be very horrible to resolve disputes. Often it was a rock wall (as mentioned above), a tree with a nail in it ( :rolleyes: ), a stream, road center, stone marker (which is now deeply buried under dirt/leaves), etc… Not to mention that the measure of angles wasn’t the most precise measurment when the original properly lines were defined. I’ve no clue how these disputes are resolved. During the building process, they needed to apply for a permit, did you object during this process? If not, I’m curious what recourse you’d have, providing that the building was done to the plan provided to the building inspector. -Butler ---
**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\ **Post date:** [August 23, 2005, 4:46pm UTC](https://boards.straightdope.com/t/land-survey-accuracy/318257/5 "2005-08-23T16:46:58Z")
The GPS stuff is mainly just for show. Vanilla GPS is accurate to a bit less than 20 meters. With special techniques, you _might_ get down to 20 cm or so. [Cite](http://en.wikipedia.org/wiki/Global_Positioning_System). But even then, the maps don’t always line up with lat. and long. as well as most people think. E.g., The place next door has sold several times since we’ve lived here. One of the earlier owners wanted a fence put in and a surveyor came out to mark the lines. He was off. It’s quite noticable: there’s a phone pole that’s 100% on my side of the line according to all the older platts and surveys. But this guy’s line went straight thru it. Fortunately, the fence was built at the other end and the result is the far corner is actually way inside the neighbor’s lot, so no real harm as far as I’m concerned. But _every_ surveyor since has just sighted the line down the fence, dropped some stakes and took off. No real surveying attempt at all. Find a surveyor with experience in doing property line disputes. More expensive but it will be documented much better and the survey will actually be done right. ---
**Author:** ![plnnr](https://avatars.discourse-cdn.com/v4/letter/p/7ea924/32.png) [@plnnr](https://boards.straightdope.com/u/plnnr)\ **Post date:** [August 23, 2005, 6:31pm UTC](https://boards.straightdope.com/t/land-survey-accuracy/318257/6 "2005-08-23T18:31:34Z")
> [@butler1850](#): > > During the building process, they needed to apply for a permit, did you object during this process? If not, I’m curious what recourse you’d have, providing that the building was done to the plan provided to the building inspector. > > -Butler Building permits approved in error can be invalidated because local governments are not estopped from correcting an error (at least here in VA). Whether or not he complained is immaterial. If the property line is in dispute, you can bet that the local government is **not** going to issue an opinion as to whose survey is correct. The location of property lines is a civil matter between the parties. ---
**Author:** ![chappachula](https://avatars.discourse-cdn.com/v4/letter/c/d2c977/32.png) [@chappachula](https://boards.straightdope.com/u/chappachula)\ **Post date:** [August 23, 2005, 7:04pm UTC](https://boards.straightdope.com/t/land-survey-accuracy/318257/7 "2005-08-23T19:04:35Z")
> [@ftg](#): > > The GPS stuff is mainly just for show. Vanilla GPS is accurate to a bit less than 20 meters. Don’t confuse sportmans GPS equipment($200 for hiking , accurate to 20 meters) with professional land surveying GPS equipment ($20,000 - accurate to millimeters) [http://www.trimble.com/mgis\_highaccuracygis.shtml](http://www.trimble.com/mgis_highaccuracygis.shtml) > [@](#): > > He was off. It’s quite noticable: there’s a phone pole that’s 100% on my side of the line according to all the older platts and surveys. But this guy’s line went straight thru it. > But _every_ surveyor since has just sighted the line down the fence, dropped some stakes and took off. No real surveying attempt at all. Land surveying is a very complex profession. That’s the reason for requiring land surveyors to be professionally licenced.Using modern electronics sounds easy, but the goal is to to re-create a boundary that was set maybe 100 years ago, and often starting with contradictory evidence. (i.e. 2 maps of neighboring lots, both maps are “official” and legal, but they don’t match up.) If you have a serious dispute which is likely to end up in court, pay a professional surveyor to measure the boundary, place his monuments at the property corners and sign the documents. ---
**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\ **Post date:** [August 23, 2005, 7:53pm UTC](https://boards.straightdope.com/t/land-survey-accuracy/318257/8 "2005-08-23T19:53:47Z")
> [@chappachula](#): > > Don’t confuse sportmans GPS equipment($200 for hiking , accurate to 20 meters) with professional land surveying GPS equipment ($20,000 - accurate to millimeters). A. That’s why _I_ differentiated between ordinary and special GPS techniques. Did you read the part that you cut off in my quote? B. From the data spec “white paper” on the very site you link to: Code differential GPS positioning Horizontal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±0.25 m +1 ppm RMS Vertical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±0.50 m +1 ppm RMS WAAS differential positioning accuracy . . . . . . . . Typically \<5 m 3DRMS Note that the ad-type pages fail to mention this info while implying greater accuracy. C. There is a _big_ difference between using GPS for _absolute_ and _relative_ positions. For surveying, you first need a couple absolute reference points. It doesn’t matter if you can measure the last corner relative to the mm if the first 2 corners are off 25cm. ---
**Author:** ![GusNSpot](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gusnspot/32/436_2.png) [@GusNSpot](https://boards.straightdope.com/u/GusNSpot)\ **Post date:** [August 23, 2005, 8:17pm UTC](https://boards.straightdope.com/t/land-survey-accuracy/318257/9 "2005-08-23T20:17:07Z")
Okay, down boys… What is the actual distance from the Golden Gate Bridge to Hawaii 5 o’s front step is one thing, and property boundary disputes are a whole nother kettle of fish. Most places have rules contingent on time in place. ie, the fence has been the accepted boundary for 15 or some such years there fore it si the boundary, no matter that the surveyor made a mistake 15 years ago. You don’t own 2 acres but you have 2.00002 acres and the other guy is out his 3"'s. ( 1 ) If you can fine a 'God" stone or a section stone set Wayyyyyyyyyyy back when. Then that is the official starting point no matter how bad it is. ( 2 ) Does the State us ‘meets and bounds’ or does it use sections and parts of sections clear on down the ‘lot’ level. ( 3 ) ( \* from this rock to that tree ::: VS :::: the N/E 1/4 of the South half of section 23 in Township 12 N and Range 5 West… \* ) Oldest and longest uncontested carries a lot of weight. My Grand Dad was on the county commissioners and the little town had a couple of old cranky butts fussing over 6’ along a mile fence. That is a lot of land. They had the hole town taking sides and disrupting everything. They could not get it settled and the courts were not helping much. So Grand Dad said, “The county needs to have a road there. You both back up 24 feet.” end of problem. Point being, be sure you want to open the can of worms before you start. Property disputes can get plum nasty… YMMV ---
**Author:** ![rbroome](https://avatars.discourse-cdn.com/v4/letter/r/838e76/32.png) [@rbroome](https://boards.straightdope.com/u/rbroome)\ **Post date:** [August 24, 2005, 12:33am UTC](https://boards.straightdope.com/t/land-survey-accuracy/318257/10 "2005-08-24T00:33:59Z")
> [@YPOD](#): > > We live in an old house (1850), as does our neighbor. I am in the process of getting my property surveyed and the guys just finished staking the property line between me and my neighbor, who appears to have built his deck and fence on our property (over our objections). The problem I have is that the surveyors placed the stakes about two to three feet from where the property line appears on the old survey (as measured from my house’s foundation). We have a copy of the last survey done before our previous neighbors moved out, which also indicates that the stakes are a little bit off. I do not yet have the final survey map from the survey company; they guys doing it simply said that I should wait for the final copy. How accurate are surveys today? Is it a matter of feet or inches? Do different surveys usually vary from each other? What do we do if the surveys differ from each other? I second (+) the recommendation for a surveyor experienced in cases such as this. Assuming you wish to pursue it. FWIW, it would be a lot cheaper and cleaner to pick any survey, both of you agree to it, go down to the courthouse and file plats. But even that isn’t easy. Remember the gov’t is a very interested player here (property taxes and all that) so nothing is going to be easy. So this is going to take a surveyor + a couple of lawyers + patience. As an aside, accurate surveys still change or don’t agree. Depending on the references, two completely accurate surveys can disagree. So there are laws and procedures for reconciling the differences. Yes, “200 yds past the stone fence” isn’t very accurate, but then again come on down to S. Louisiana 🙂 where I live. The most modern differential GPS system in existance doesn’t help much if the the land is distorting both horizontally and vertically in a matter of a few years. Yes, that point in space relative to the satellites didn’t change, but if _everything_ around it does-how does that effect the survey? 🙂 I know of property sitting on drained swamp that is above sea level if surveyed from one USGS marker, and below sea level if surveyed from another-and both markers are accurately placed. Explain that to the insurance company when you try to insure your building! ---
**Author:** ![Civil\_Guy](https://avatars.discourse-cdn.com/v4/letter/c/d78d45/32.png) [@Civil\_Guy](https://boards.straightdope.com/u/Civil_Guy)\ **Post date:** [August 24, 2005, 2:10am UTC](https://boards.straightdope.com/t/land-survey-accuracy/318257/11 "2005-08-24T02:10:43Z")
Agreed, good surveyors will make a big difference. The bit about the accuracy of GPS is a little misleading: not everything _has_ to be done with GPS, nor should it be, if there is any doubt about its accuracy. The surveying pros will know their equipment, and which is best for which purpose. They will determine the “closure error” and they won’t be happy unless it’s a tight number. I _am_ a surveyor (but haven’t practiced hardly ever) but I am not your surveyor, et cetera. The pros will try to determine the best starting point that they can, based on available records (of course, “best” is relative, not absolute). They’ll try to get enough redundancy and checking into the process to satisfy professional pride and the state license board. Survey monuments don’t always have to be placed exactly on the boundary line, as long as the surveyors produce the official documents that say how one can determine the boundary line from the monuments. They might do this, for instance, if they thought there was good chance the boundary line might get messed up from future construction, et cetera. When you can, get a copy of whatever official records they file, and then go seek expert advice. ---
**Author:** ![MaryEFoo](https://avatars.discourse-cdn.com/v4/letter/m/ba8739/32.png) [@MaryEFoo](https://boards.straightdope.com/u/MaryEFoo)\ **Post date:** [August 24, 2005, 5:28am UTC](https://boards.straightdope.com/t/land-survey-accuracy/318257/12 "2005-08-24T05:28:32Z")
Seems you have good answers above. Here’s an anecdote that might illustrate > [@](#): > > I do not yet have the final survey map from the survey company; they guys doing it simply said that I should wait for the final copy. My brothers went to Alaska to do a survey. The land covered the tip of a forested peninsula that was owned by a Monterey realtor and hotshot. Behind that acreage was national wilderness or some such vacant, publicly owned land, so all this was pretty remote (access by boat or helicopter). My older brother had just finished two years at Monterey Peninsula Junior College and was now a licensed surveyor. My younger brother came along as assistant. Hotshot was in a hurry since he was already selling lots, and he didn’t know which ones were going to turn out to be under water (there was a pond/swamp there). My brothers, among some amazing adventures\*, conscientiously got to work and did their surveying. They roughed out a path where they guestimated the back property line would be, and then did the proper measurements, which made the true line about a yard off the rough path. The rough path happened to include stakes, which they’d put there to keep track, **not** as official boundary stakes. Then Hotshot brought up a couple of guys\*\*, buyers or investors, who simply took the rough path as the God-given property line in spite of being informed otherwise by the surveyors. So, it’s the final signed copy of the survey that is official, not necessarily the stakes. But you probably want to get ready to address this as per informed suggestions above. \*Hotshot provided provisions, IIR what my bros said provisions consisted of ten pounds of baking powder and no flour. So they had to catch their food. Also the cabin burned down when it stopped raining for a few days and the shingles caught fire from the stovepipe. They ran to the cabin and ran in to grab sleeping bags and stuff, and when the bullets started going off in the fire they scrambled out of there, then the banging stopped and they tried for more except the firing started again, etc. \*\*referred to as Pistol McChainsaw and his friend by my bros, due to their intense use of these Wilderness Hero tools, scaring any game except squirrels for miles away, and shooting at the squirrels. And missing. ---
**Author:** ![Soylent\_Gene](https://avatars.discourse-cdn.com/v4/letter/s/ecae2f/32.png) [@Soylent\_Gene](https://boards.straightdope.com/u/Soylent_Gene)\ **Post date:** [August 24, 2005, 6:26am UTC](https://boards.straightdope.com/t/land-survey-accuracy/318257/13 "2005-08-24T06:26:48Z")
> [@chappachula](#): > > Don’t confuse sportmans GPS equipment($200 for hiking , accurate to 20 meters) with professional land surveying GPS equipment ($20,000 - accurate to millimeters) > [http://www.trimble.com/mgis\_highaccuracygis.shtml](http://www.trimble.com/mgis_highaccuracygis.shtml) The link did not indicate accuracy of the unit. I have experience using Trimble GeoXT equipment with real-time correction, and I am not aware of anything that gets millimeter accuracy (it’s typically sub-meter accuracy at best). I’d like to see some backup information on this claim if true. I have also never heard of legal property survey’s being condcuted by GPS. Am I living in a cave? ---
**Author:** ![Soylent\_Gene](https://avatars.discourse-cdn.com/v4/letter/s/ecae2f/32.png) [@Soylent\_Gene](https://boards.straightdope.com/u/Soylent_Gene)\ **Post date:** [August 24, 2005, 6:28am UTC](https://boards.straightdope.com/t/land-survey-accuracy/318257/14 "2005-08-24T06:28:51Z")
Another thing to consider - the beacon receiving unit on the Trimble’s is about 4 inches in diameter. How could you get millimeter accuracy with this? ---
**Author:** ![BobLibDem](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/boblibdem/32/3149_2.png) [@BobLibDem](https://boards.straightdope.com/u/BobLibDem)\ **Post date:** [August 24, 2005, 10:33am UTC](https://boards.straightdope.com/t/land-survey-accuracy/318257/15 "2005-08-24T10:33:01Z")
I rather doubt the accuracy of GPS equipment is even a factor. Your property description is going to reference a section line and have several directions and distances. There isn’t going to be anything of value obtained from GPS. ---
**Author:** ![mks57](https://avatars.discourse-cdn.com/v4/letter/m/b9bd4f/32.png) [@mks57](https://boards.straightdope.com/u/mks57)\ **Post date:** [August 24, 2005, 10:35am UTC](https://boards.straightdope.com/t/land-survey-accuracy/318257/16 "2005-08-24T10:35:51Z")
> [@Soylent Gene](#): > > Another thing to consider - the beacon receiving unit on the Trimble’s is about 4 inches in diameter. How could you get millimeter accuracy with this? That should be irrelevant, as long as the geometry is fixed. The delay in the antenna and feed system can be measured with high precision. ---
**Author:** ![GusNSpot](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gusnspot/32/436_2.png) [@GusNSpot](https://boards.straightdope.com/u/GusNSpot)\ **Post date:** [August 24, 2005, 2:04pm UTC](https://boards.straightdope.com/t/land-survey-accuracy/318257/17 "2005-08-24T14:04:07Z")
> [@Soylent Gene](#): > > The link did not indicate accuracy of the unit. I have experience using Trimble GeoXT equipment with real-time correction, and I am not aware of anything that gets millimeter accuracy (it’s typically sub-meter accuracy at best). I’d like to see some backup information on this claim if true. > > I have also never heard of legal property survey’s being condcuted by GPS. Am I living in a cave? All I can say is that I have worked with this equipment and it does do this. You really need to go visit a survey outfit that does this… You seem to know nothing of the HARN makers, nor the way the dishes ( antennas ) are put up over the points to be surveyed. Might go talk to an aerial Mapping company that uses this to do actual aerial triangulation on their camera in flight. You will be amazed at what is and can be done today with this stuff. High degrees of accuracy are usually derived from a system of concurrently running devices. Demanding technical explanations from those that use this stuff because you are not familiar with it is not cool. You won’t get a whole course on what it can do here. Got to an seminar put on by Trimble and ask them your questions or demand that they prove to you that it works… That shoe is really on the your foot. They ( the machines and the surveyors themselves ) produce the results, you prove that they are wrong because the rest of the world has already accepted the evidence… YMMV