Does anyone have a formula or knowledge of a website whereGPS numbers can be found using plat book descriptions. I have a chance to buy a high and dry section of swamp area that has not been survied except one cornor of an adjasent area; and there are no roads or markers in the area. Thanks

-- mitch hearn (moopups1@aol.com), May 04, 2001

Answers

Response to GPS numbers?platbooks

Do you have access to a new range and township map?? General surveys of the entire country (with possible exception of Alaska) were completed in the late 30's. They were done by section mainly (640 acres), and any RT map newer than 1990 will have coordinates down to 160 acres, sometimes less. Within that, it should be easy to find your land. Problem is, they won't have GPS coordinates. However, these maps are indispensible for locating property (need the info from this map for your new plat of survey), knowing exactly the lines for hunting and fishing districts, etc etc.

I take it you don't own a GPS?? They are good to have, and a relatively decent one can be had for less than $100. I'd get one.

You can check the US Geological Survey site - they will have more answers for you. Also, call the county extension office. They should know which maps will help you, and should have them at the office.

-- Sue Diederich (willow666@rocketmail.com), May 04, 2001.

Response to GPS numbers?platbooks

Try going to this website: http://terraserver.homeadvisor.msn.com You can put in an address, location, etc. and get an ariel view of the place.

-- Rose Marie Wild (wintersongfarm@yahoo.com), May 04, 2001.

Response to GPS numbers?platbooks

Mitch, You might try this. GO to your county recorder's office and get the latitude and longitude coordinates of the corners of your land. (Someone there ought to be able to calculate them for you if they are not marked on the platt maps.) The GPS units provides the location of the receiver in latitude and longitude and with a little practice you can navigate using a GPS unit. A Magellan unit costs under $100; however, a local hunter or outdoorsman might have one you can use. Good luck.

-- Lynn Goltz (lynngoltz@aol.com), May 04, 2001.

Response to GPS numbers?platbooks

I got the coordinates for our property through the BLM. Once I had the township designator and the section number they were able to send me a coded "map" of that section which identified the four corners and the midpoints along each side (effectively dividing it into quarter sections). Each corner had a designator code, which could be translated into longitude and latitude. The translation came from a database called The Geographic Coordinates Data Base or G.C.D.B. The only caution he gave us was not to use the "normal" parameters for the GPS gear, apparently know as NAD 27, but to use a setting of NAD 83. I'm not clear on this point yet as we haven't had the opportunity get our hands on a GPS device and/or the time to figure out how to use it and what the heck these NAD settings are. He explained that it effects the accuracy as in an aircraft it's NAD 27 and on the ground it's NAD 83. And this may be NAD settings for our area (Lordsburg, New Mexico area) yours may be different. Anyway, the BLM chaps were quite helpful and emailed me the decoding portion of the database that I needed and explained how to decode it and seemed to know their stuff. You still may find yourself faced with an accuracy of only about +/- 30 to 50 feet - or greater depending upon the accuracy of your unit.

-- Willy Allen (willyallen2@yahoo.com), May 04, 2001.

Response to GPS numbers?platbooks

I'm a licensed land surveyor. Unless you have survey grade GPS receivers (plural - takes at least two) don't be suckered into believing you can come any closer than ball park at establishing a property corner by coordinates. That $100 receiver that the salesman tells you is accurate to within 30 meters (100 feet) isn't really. If you don't believe me, borrow or rent one and then take readings every couple hours over a 24 hour period at the exact same location and see how far your "coordinates" move with every observation. Accuracy is all relative. Coordinates are a tool that we use. They are not the legal definition of property boundaries. Yes, you can get "coordinates" from the BLM for some areas, or you can scale Latitude/Longitude from a USGS Quad Map, but unless you understand the principles of accuracy versus precision, the origin and meaning of those coordinates, and what to do with them, you will have no idea if you are anywhere close to the truth of where your corner is supposed to be. You would do better with a compass and tape. But there again, you better understand such things as magnetic declination, local attraction, and how to correct for it. What is the basis of bearings used in your legal description, or does your legal description even use bearnings? Is it subdivisional? My advice: Hire a professional land surveyor, or make your offer contingent on a survey by a licensed surveyor.

The saying that "a person who represents himself in court has a fool for a lawyer" applies to the layman who thinks he can survey his own land as well as a professional surveyor.

-- Skip Walton (sundaycreek@gnrac.net), May 05, 2001.

Response to GPS numbers?platbooks

More on geographic coordinates: GPS receivers work primarily in Geographic Coordinates: Latitude and Longitude. NAD 27 and NAD 83 refer to the North American Datum of 1927 and North American Datum of 1983. There is also a 1991 adjustment of the NAD 83. These various datums use different models of the Earth's surface. If your receiver can translate Lat/Long into Northing/Easting coordinates, they will be expressed in a State Plane Coordinate system. Every state in the US uses it's own statewide coordinate system which is based on either a Lambert or Mercator projection. Distances derived from coordinate values in a state plane coordinate system are not the same as actual ground distances, which are the legal basis for property descriptions. Depending on your elevation and local on the state plane grid, the scale factor between grid and ground distances can be significant. This all becomes so complex that even some older surveyors cannot grasp the mathmatical concepts required to work with state plane and geographic coordinate systems. GPS surveying is becoming a specialty field within surveying. Handheld GPS receivers are fine for navigation, but are never used for surveying. For about $20,000 you can get a resource grade GPS setup. This is used for inventory of infrastructure by utility companies and public works departments where high accuracy is not required. In land surveying we use highly accurate receivers and a procedure called "differential GPS" where we have receivers on two base stations with known coordinates and one or more rovers making simultaneous observations at new positions on which we want to establish accurate geodetic positioning. We then take all the data back to the office, download it into the computer and process the data to obtain coordinantes which can be verified for both accuracy and precision. Because there are two base stations, every observation has redundancy with double vectors to each unknown position. With this methodology we routinly obtain sub-centimeter accuracy.

Assuming you had good coordinates to start with, the best you could hope for with a hand held GPS receiver is +/- 100 meters. In reality, if you don't understand the basics of geodesy and coordinate systems, you really won't have the faintest clue as to where you are. Any BLM staff person who hands out coordinates and programs to the layman is a goon and should be severely reprimanded for professional negligence.

-- Skip Walton (sundaycreek@gnrac.net), May 05, 2001.

A very good site is:

http://www.topozone.com

You can even see your house on it! And it has the cordinates on there also. Ask the electric company also. They came here to our farm and "pinpointed" each and every pole by using a hand-held computer and pointing it at a satalitte! She had a satalitte dish sticking out of her backpack, about 3 feet high. I knew the very exact location on the globe where my farm was!

-- Cindy in KY (solidrockranch@hotmail.com), May 05, 2001.

Cindy. Please define "exact". It certainly is not same level of exactness that you expect to know where your property corner is. The power company doesn't need to know and doesn't care "exactly" where their facilities are. What they are doing is collecting inventory for a GIS (Geographic Information System). If their position is within 100', that's good enough, and that's about as good as anyone can expect using the system you described. What the system gives them is a map based database that tells them approximately where their poles are, the pole number and any other data related to that pole. They don't need to know "exactly" where that pole is. +/- 100' is good enough because when the lineman gets that close, he can see it!

As I stated in my first response, I am a licensed land surveyor. If anyone is foolish enough to think they can survey their boundaries with a handheld GPS unit and coordinates they pull off some website, then by all means, go ahead. It will cost you a lot more later when your neighbor threatens law suit for your encroachment. I always charge more for my services when I get hired to help resolve a boundary dispute becuase I know I may have to defend my survey in court. I like boundary disputes, they result in good profits for us surveyors. So don't think I'm just trying to promote our profession by warning you not to try to do your own boundary location with a navigation grade GPS receiver and some "coordinates" that you have no idea what they mean.

-- Skip Walton (sundaycreek@gnrac.net), May 06, 2001.

Skip, if I camped on site for a day (or so) and took a number of GPS fixes would the average be reliable? I understand many navigation techniques rely on sucessive approximations.

-- john hill (john@cnd.co.nz), May 06, 2001.

Thank you for the thinking peoples responses, I am furtherly convinced that homesteaders do more than just break saddle goats and milk donkeys!

-- mitch hearn (moopups1@aol.com), May 07, 2001.

Skip, I agree with you that a hand-held GPS unit isn't much good for marking boundries, but it's not as bad as you imply. Averaging readings for a minute or so, my day-to-day repeatablity is better than 20'--assuning I pick a time when there are a number of satelites in view. This winter they put a section marker on one of my property lines. I haven't taken the time yet to see what the state thinks it coords are. Once I get around to that, I'll use it to check accuracy as well as precision.

==>paul

-- paul (p@ledgewood-consulting.com), May 08, 2001.

You're right Skip! Those bums at the BLM, the nerve, giving out public information to the public, the gathering of which was paid for by the public. Boy 'O' Boy...

-- Willy Allen (willyallen2@yahoo.com), May 10, 2001.