Locating property pins with a GNSS Land Meter 3

[RARWOOD]

I am a retired Civil Eng. with a piece of property where I have two known property pins. I need to locate the others and wonder if I can use a GNSS Land Meter to locate the others. I have tried to use GIS sites to locate the GPS coordinates or longitude and latitude without much luck.

 

[IRstuff]

It'll likely depend on what exactly the GNSS does. The default accuracy for most such systems is about 2.5 meters, which is possibly a relatively large area to search for something small. Some sort of RTK (real time kinematics) GNSS can achieve cm-level accuracy, but requires a base station in proximity which has its own exact location on Earth and corrects for the GPS uncertainties for the roving receiver. Alternately, there are GNSS receivers that record everything and can correct their positions after the fact, but those tend to slightly less accurate, but you could do basically a "guess and try" with such systems, i.e., take a reading, download to laptop and run the correction software, etc. I think, though, the free correction data tends to be time-lagged, i.e., you're not going to get real-time corrections without paying some fees.

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[1503-44]

Not sure what you mean by "Locate" the pins.

Does that mean you know where the pins are and you want their UTM coordinates, or lat/lon?

What data do you have now? Usually property has a legal survey, plat, or bearing and distance description. Do you have a property plat? Do you have distance and bearings between pins list? This information is typically available at the local property registry office.

Where are the pins with known locations?
What is your accuracy tollerence?








--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[TerryScan]

Do you have a plat or deed description of the land? Do you have a metal detector?

A typical workflow would be:

1. Use your device to determine the coordinates of your two known points.

a. does the distance between the points agree with the plat?​

2. Use Coordinate Geometry to calculate the Coordinates for all other boundary points from the plat or deed.

a. one may need to rotate/translate the coordinates if they are not on the same coordinate system as those measured with your device​

3. Use the calculated boundary coordinates as "look for" points to search for the other boundary monuments
4. When one is close to the "look for" location, use metal detector to search for pins.

 

[IRstuff]

I have two known property pins.

If you have two pins, you could alternatively triangulate the remaining pins with a total station, assuming you have a reasonable property map.

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[RARWOOD]

I want to thank every one for their replies! Regarding the replies:

1. I have a plat map & metal detector.

2. I am trying to find the GPS coordinates of the known property pins. I am also interested in Lat. & Lon. However based on my memory of working on survey crews when I was in college, I should be able to get Lat. & Lon. from the plat map.

3. I need to review coordinate geometry. I have an old surveying book, copy write 1953 which I have been reading through.

4. I am hoping I just need to get close and then use a metal detector to locate any buried pins if they are there.

5. Actually if I had someone to help me I have a transit I could use to locate the pins.

The real problem relates to a property pin at the corner of property jointly owned by a number of owners. My wife and own a cabin on a MN lake. Our lot is lot 16 of a 31 lot group. Adjacent to the lots is 29 acres of land jointly owned by the owners of the 31 lots. Another property owner is using a corner of the jointly owned property. So at this time I really only need to locate one pin to try to resolve the issue of the property dispute.

Since we are in a rural area the question is would the cost to hire a surveyor to locate one pin exceed the cost of renting a total station for a week.

Thank you all again for your replies.

 

[IRstuff]

What's the approximate distance to the pin in question?

You, and a helper with a pole and spray paint
> set the transit on one of non-adjacent pins
> pole on the adjacent pin
> baseline to that pole
> set transit to angle where the desired pin should be
> move pole to transit sight line and follow sight line to approximate location of desired pin, using spray paint on ground to record line of sight
> move transit to adjacent pin and repeat abovr
> intersection of lines of sight should be the approximate location of pin

if the distance is relatively short, a cheap laser rangefinder can be used to dial in the distance to the desired pin from the known pins, a corner cube, bicycle reflector, or Scotchlite reflector tape can be used to boost laser return signal.

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[1503-44]

Latitude and long is probably not be referenced on a plat. Depends on how old it is.

In MN, pins could be referenced only by Northings and Easting distances in feet to the section number's corner in the Range and Township system.

Another common reference may be to the State's coordinate system Northings and Eastings in feet.

Then again, some plats may not even have a reference to any system , being just a list of distances and bearings from one pin to the next. Sometimes being referenced to a promenate rock, a nail in an old tree, or some other easily recognised landmark. Sometimes you get a plat drawing, sometimes just a list.

GPS native format is latitude and longitude, often with the possibility to read the UTM Zone with coordinates of Northings and Eastings in meters.

If you have reference distances to any one of the systems above, those can be converted into the other systems, usually involving taking sines and cosiness of a long list of offset parameters. Fortunately a good GIS program can handle those conversions for you.

If you have NO reference to any of those systems, then you will need a GPS to get the UTM coordinates, or latitude/longs. You do not need a TotalStation.
I use the GPS in both my tablet and in my phone.
You do need a program to access the coordinates easily.
It's free. No high accuracy totalstation data charges either.
The program I use is GPSTEST. You can download it for android at the Playstore.
GPSTest will read out and create a log of the GPS info.

The only question is the accuracy of the GPS signals. I do the high accuracy procedure myself.
After 30 minutes of observation, or data logging, I see that all values are within +/- 10ft (+/-3m) about +/- 0.0000350 degrees lat/lon) orbiting about a about the mean values of lat & long. As 3m is the typically available accuracy, I take the mean values of all values logged as the true lat/longitude. The mean might change slightly, if you observe for longer period of time, but not much. You absolutely will be able to find your pin using mean values taken over a 30 minutes timespan as the true lat/long.

Once you have the mean lat and long values, or UTM values, you can convert to any other system you want.

But you must be able to locate the pins. if you are not able to see a pin, you must have a bearing and distance from a known pin to the next pin and so on. With the bearings and distances, you can calculate the northings and eastings of your reference system. The differences between coordinates in the state system are the distances north and east between pins, in feet, or in meters if you are using UTM zones and N/E offsets.



Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[RARWOOD]

1503-44 Thank you for your reply. Part of my problem while I worked on surveying during the summers when I was in college, I did not prepare plat maps or work with them. I also need to learn more about GIS maps and programs.

When I started my project I thought I could set up a transit on one of my property pins sight down to another pin. Then turn an angle to establish a new bearing. After measuring the property line distance I thought I would end up at the approximate location of the pin I am looking for.

However now that I am looking closely at my plat map I can see that to use it I have to convert some of the information. At one of the property corners the map gives an angle of 14 degrees. However on the map the angle is over 90 degrees. From reading my old survey book I think that is an angle off the north south section line. I also don't know how to interpret the information given along one of the property lines. The distance between the pins is 266.19' the other information is N 71 degrees 28" 20" E. I have tried to attach a copy of my plat map but I don't know if it worked correctly.

I need to find a surveyor who has recently done some work in the area where my cabin is. I know there is one owner on the lake who brought a new piece of property on the lake and had it surveyed about three years ago. I need to find out who he used.

Actually my problem involving the jointly owned property may be easier to solve than I thought. Looking at the plat map it looks like the pin I need to locate is on a section line and about 750' from a section corner

Thanks again for your help.

 

[Ingenuity]

RARWOOD:

Based up the length data you provided, you are talking about lot #16.

If I am correct, then the 14° you refer is Δ, the subtended angle for the arc segment along WILDERNESS WAY. Interestingly, it does not give you the arc radius, R, but the opposite side of the WAY does, so you can calculate the radius on your property line (+ 66.00 feet to make a R of 210.75'). The L of 55.00 is the arc lengh of the curved boundary.

The N 71° 28" 20" E is simply the bearing quadrant, with NORTH running RIGHT to LEFT on the plat survey.

Knowing the line of N 71° 28" 20" E (with distance 266.19') then you should be able to use a theodolite/transit or a total station to field locate the other boundary points.

 

[Ingenuity]

I input it into AUTOCAD and all the bearing quadrants and distance, arc lengths etc all check out...as they should.

 

[RARWOOD]

Thank you again for your help. I am glad you mentioned AUTOCAD. I have Turbocad and it never occurred to me that i could make use of it to help me solve my problem.

Locating the property pins for my lot 16 is not a major issue. My know pins are the two outside corner pins at the lake end of the lot. At some point in time I want to add a shed. To maintain the correct property line set back I will need to know the approximate location of the property line.

Regarding the joint owned property I need to get an estimate from a surveyor on the cost of locating the pin. I have checked on renting a total station. As I told the person at the rental place it is a question of cost. When I get an estimate from a surveyor I can compare it to the rental cost of a total station.

Than you all again. I am learning a lot and see that I would benefit from reading more about creating plat maps.

 

[1503-44]

Here is the pdf map overlayed onto Google Earth
I have numbered the principal points, 1 through 6

These are the APPROXIMATE longitude and latitudes of those points

POINT COORDINATES DEGREES AND DECIMAL DEGREES

LONGITUDE (-WEST), LATITUDE (+NORTH)
<name>1</name><coordinates>-93.38075667029992,46.62712840995998</coordinates>
<name>2</name><coordinates>-93.38081037214721,46.62733521659605</coordinates>
<name>3</name><coordinates>-93.38087606402392,46.62738899410758</coordinates>
<name>4</name><coordinates>-93.38184130733794,46.62718779073304</coordinates>
<name>5</name><coordinates>-93.38194479531761,46.62704345547674</coordinates>
<name>6</name><coordinates>-93.38210021622741,46.62685394987196</coordinates>

If you turn on the Google Maps App in your phone and watch the latitude and longitude as you walk around there, you may be able to find all the pins. Google Maps have some inaccuracies at times, so I can't tell you how far away from each dot you might actually find the pins, but they should be within a couple-three meters. If there are pins there, I think you will probably be able to find them.

I have attached the kml file of the overlay and point placemarks. Open that file with Google Earth and you can see it too.

Nice boat.



--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[RARWOOD]

thank you very much. The information you provided will definitely help me find the pins or at least get close.

 

[RARWOOD]

This weekend I was up at the lake and tried out my GNSS Land Meter. I started at points 1 & 3 because their are pins at those two locations.

At point 1 I got a reading of 93.3808,46.6271

At point 3 I got a reading of 93.3816,46.6271

In the area of point 4 I got a reading of 93.3807,46.6271
At one time there was a wood stake in the area of around point 4.
When I took my reading I was just guessing on where the stake use to be.

I won't be able to go up again until after the 15th. However the next time I go up I can stay longer and will take a metal detector with me.

1503-44 When you developed the Google Earth overlay did you use a program like Land Glide?

IRstuff: What type of correction software is available?

 

[IRstuff]

The RTK-capable GNSS receivers all have their own software for inputting RTK corrections.

Saw this on Friday

https://www.sparkfun.com/products/2...636&utm_content=305457673&utm_source=hs_email

The GNSS receiver manufacturer sells RTK correction data, although there appears to be a free-ish tier.

https://portal.thingstream.io/pricing/

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

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[RARWOOD]

IRstuff & TTFN Thank you again. I beginning ti think I need to take a surveying course at the local junior college or online.

 

[IRstuff]

I beginning ti think I need to take a surveying course at the local junior college or online.

Only if you really enjoy the subject ;-) I think that given the one-off nature of this task, Googling relevant information is probably adequate. At the one end, 1503-44's and Ingenuity's mapping of your plat map onto an actual map should allow you to directly triangulate the location of the other pins using the known pin locations as a baseline, using your transit and a tall pole with some sort of surveyor-ish target, i.e., black on white crosshairs. A decent transit with, say, 30 arcsec accuracy hypothetically can locate a target within inches over a 450 ft distance.

RTK using off-the-shelf software/hardware is really mostly plug & play; not much theory is required.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

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[1503-44]

The RTK systems are really only needed for centimeter accuracy in real time situations. The hype is about using RTK networks to keep the Teslas inside the white lines. If you are not doing letting Tesla do the driving, time is on your side and no RTK needed.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[udraft]

Couple things to add. The GPS on your phone is only accurate to 20-30 feet.
2. I am trying to find the GPS coordinates of the known property pins. I am also interested in Lat. & Lon. However based on my memory of working on survey crews when I was in college, I should be able to get Lat. & Lon. from the plat map.
At least where I live (Ohio, USA) plats only require metes and bounds tied to a known point, often a section or lot corner. I wish they would require local coordinates (State Plane) or geodetic coordinates, some day.
Your best bet is to use the 2 pins you have to traverse to the others by the metes and bounds.