Can You Interpret These Land Survey Numbers?

[TromboneAl]

Here are two pages from a survey. Each line of numbers apparently refers to the numbered location on the chart, and seems related to the marker CP101, which I have located.

Does anyone know what these numbers mean? Is there any way to find a given location based on those numbers?

Thanks.

 

[SecondCor521]

My guess is that they are parameters for Bezier curves.

https://en.wikipedia.org/wiki/Bézier_curve

That's all I got.

 

[Bamaman]

I'd sure hate to pay for a survey and get it back without a map and numbers on it. Unless they're understood, they're worthless.

 

[SecondCor521]

I'd sure hate to pay for a survey and get it back without a map and numbers on it. Unless they're understood, they're worthless.

1. Do survey. Charge money.
2. Interpret survey results. Charge money.
3. Profit!

 

[target2019]

Sure looks like lat-long for each point.

 

[CRLLS]

My best guess is that these are cartesian coordinates. Units? I'm not sure if feet, yards meters or? I would further guess that CP101 is point 18 on your map. Units can be inferred by finding other iron lot markers and comparing to the chart provided.

 

[MikeWillRetire]

The table looks like a list of the coordinates of the points on the map. The first column is the point number. The second column looks like the northing, and the second column is easting. For example, point 1 has a northing of 2872.8 and point 2 has a northing of 2972.2. That means that point 2 is about 100-feet north of point 1.

 

[Ronstar]

The table looks like a list of the coordinates of the points on the map. The first column is the point number. The second column looks like the northing, and the second column is easting. For example, point 1 has a northing of 2872.8 and point 2 has a northing of 2972.2. That means that point 2 is about 100-feet north of point 1.

^This is it. Most likely in feet. And they are based on an arbitrary coordinate base. Not latitude or longitude. Disregard the 4th column. It is for elevation, but your surveyor didn't do elevations. So the data in column 4 is null. The 5th column is just the description of the point.

Distance between any 2 points is ((N1-N2)^2+(E1-E2)^2)^.5. Where N is the north coordinate, and E is the east coordinate. Just subtract the north coordinate from another northing. Square that. Do the same for the eastings. Add the difference in the northings squared to the difference in the eastings squared, and then take the square root. This will give you the distance between the coordinate points. Based on the Pythagorean Theorem.

For example, the difference in the northings of 8 to 2 is 2988.2256 (northing of 8) minus 2972.2426 (northing of 2) is 15.983'. Easting difference is 4495.4602-4644.6062 or -149.146. Square the northing difference of 15.983 is 255.46. Square the easting difference of -149.146 is 22244.53. Add 22244.53 and 255.46 to get 22499.99. Take the square root of that to get 150.00' between points 2 and 8.

 

[LEDBET]

^This is it. Most likely in feet. And they are based on an arbitrary coordinate base. Not latitude or longitude. Disregard the 4th column. It is for elevation, but your surveyor didn't do elevations. So the data in column 4 is null. The 5th column is just the description of the point.

Distance between any 2 points is ((N1-N2)^2+(E1-E2)^2)^.5. Where N is the north coordinate, and E is the east coordinate. Just subtract the north coordinate from another northing. Square that. Do the same for the eastings. Add the difference in the northings squared to the difference in the eastings squared, and then take the square root. This will give you the distance between the coordinate points. Based on the Pythagorean Theorem.

For example, the difference in the northings of 8 to 2 is 2988.2256 (northing of 8) minus 2972.2426 (northing of 2) is 15.983'. Easting difference is 4495.4602-4644.6062 or -149.146. Square the northing difference of 15.983 is 255.46. Square the easting difference of -149.146 is 22244.53. Add 22244.53 and 255.46 to get 22499.99. Take the square root of that to get 150.00' between points 2 and 8.

This is spot on. Survey worksheet with a coordinate list.

 

[TromboneAl]

Thanks.

Something doesn't add up. The numbers say that point 17 is 13 feet north of Point 18 (and about the same amount north of CP101). But it can't be more than a few feet.

 

[ExFlyBoy5]

^This is it. Most likely in feet. And they are based on an arbitrary coordinate base. Not latitude or longitude. Disregard the 4th column. It is for elevation, but your surveyor didn't do elevations. So the data in column 4 is null. The 5th column is just the description of the point.

Distance between any 2 points is ((N1-N2)^2+(E1-E2)^2)^.5. Where N is the north coordinate, and E is the east coordinate. Just subtract the north coordinate from another northing. Square that. Do the same for the eastings. Add the difference in the northings squared to the difference in the eastings squared, and then take the square root. This will give you the distance between the coordinate points. Based on the Pythagorean Theorem.

For example, the difference in the northings of 8 to 2 is 2988.2256 (northing of 8) minus 2972.2426 (northing of 2) is 15.983'. Easting difference is 4495.4602-4644.6062 or -149.146. Square the northing difference of 15.983 is 255.46. Square the easting difference of -149.146 is 22244.53. Add 22244.53 and 255.46 to get 22499.99. Take the square root of that to get 150.00' between points 2 and 8.

I think I recall doing this in 3rd grade...right after learning cursive.

 

[Ronstar]

.....But it can't be more than a few feet.

I assume you found survey stakes about a few feet apart. And you think that those points are 17 and 18. They probably are not. One may be cp #101. Are something else. Usually when the survey point list has “calc” in the last field for a description, that means that there is no stake at that coordinate point - it’s a calculated point that the surveyor calculated based on dimensions on the subdivision plat.

 

[The Cosmic Avenger]

Sure looks like lat-long for each point.

That's what I thought at first, but it would put it in the middle of the Atlantic Ocean. Or if they're really both positive numbers, probably Saudi Arabia.

 

[The Cosmic Avenger]

Al, I think you need to find the index diagram for your town or county's plat or master index. I think it's something like the "index" part of this tutorial for searching historical land records: https://www.blm.gov/or/landrecords/files/BLM_notes_plat_viewer_instructions.pdf

 

[Sittingduck]

Ronstar,

I found your expertise with surveying quite amusing after noting your location description
LOL

 

[TromboneAl]

I assume you found survey stakes about a few feet apart. And you think that those points are 17 and 18. They probably are not. One may be cp #101. Are something else. Usually when the survey point list has “calc” in the last field for a description, that means that there is no stake at that coordinate point - it’s a calculated point that the surveyor calculated based on dimensions on the subdivision plat.

Well, there are no stakes. I'm just looking at the diagram.

That CP#101 looks very official, and is a few feet from the edge of the road.

If 17 was 13' north of that, it would past the midpoint of that driveway.

 

[Ronstar]

You really can’t do much analysis with the diagram if you don’t have the coordinates of cp 101. CP101 is not a lot corner, it’s only a temporary survey point used to measure to other points. I don’t see how you figure that 17 is 13’ north of cp101 if you don’t have coordinates of 101. Don’t confuse 18 with 101. Even though they look close on the diagram, you really need the coordinates of 101 before analyzing this with any kind of precision. And it would help to know for certain that the nail in your photo is 101. Maybe there’s another nail in the area.

 

[NW-Bound]

Yes, the pairs of numbers are Cartesian coordinates, and the unit of measurement is in feet because if in meters the lots would be quite large.

I wonder if the northing and easting are arbitrary or if they are based on a transverse Mercator projection such as used in the UTM (Universal Transverse Mercator) map system and the MGRS (Military Grid Reference System) by the military. In the UTM and MGRS systems, the northing and easting coordinates are not arbitrary, but rather an absolute Cartesian XY coordinate pair that corresponds to a particular latitude/longitude pair.

I have read that in the civilian sector, states or counties have their own State Plane Coordinate Systems. If the numbers that T-Al has are in such a coordinate system, then the "arbitrary axis system" is not something that the surveyor made up, but is already defined by the local government. Then, there is certainly a way to reference to a local datum in the area, which defines the origin of this "arbitrary coordinate".

 

[Ronstar]

^ the coordinates in the list could be from a defined regional coordinate system (state plane, utm) but the list shows truncated values if they are from a defined system. There would be negative coordinates about a half mile away if they were true defined coordinates. That doesn't happen. Usually coordinates from a defined regional system have values in hundreds of thousands or millions of feet so as to not have negative coordinates within the area covered by the coordinate system.

They could be based on a local datum, but even then there would be negative coordinates about a half mile away. Not likely. IMO, the coordinates are either truncated values from a local or regional mapping system, or are from an arbitrary system.

The survey drawing and coordinate list shown is not something that is usually given to a property owner. It is for the surveyor's own use - a record of how he/she did their survey - just for their files

Normally the lot corners are staked and a drawing (plat) is made and given to the client. If Al hired the surveyor, I recommend that he ask for a Plat of Survey. Or at least ask the surveyor how he can figure out where the lot corners are based on the diagram and coordinates that were provided.

 

[NW-Bound]

... They could be based on a local datum, but even then there would be negative coordinates about a half mile away. Not likely. IMO, the coordinates are either truncated values from a local or regional mapping system, or are from an arbitrary system.

The survey drawing and coordinate list shown is not something that is usually given to a property owner. It is for the surveyor's own use - a record of how he/she did their survey - just for their files

Yes, usually a bias value is added to the mathematical projected northing and easting so that the coordinates are always positive. And yes, truncation of a very large coordinate number would make sense if it does not cause confusion when the leading digit overflows into the higher significant digit to the left.

I don't know about the customs used by surveyors, but the coordinate specification to the 0.0001 ft is peculiar. That's 1.2 mil (1/1000 of an inch)! For comparison, a piece of paper is usually about 4 mil thick.

Obviously, no surveyor can measure anything down to less than a paper thickness. It would be most likely that these numbers are the results of a calculation to convert from something else, such as geodetic latitude and longitude, into this "unknown" coordinate system. And a computer can carry out any formula to an arbitrary very fine resolution, even though the inputs entered to the formula are not that precisely known.

 

[LEDBET]

If you tell me what points on the diagram you want to know distances between I will give them to you tomorrow...

CP101 is Control Point 101 This is a survey control point that the instrument was setup over. Only thing special about it is that the surveyor could probably see many of the numbered points from it for survey location with the instrument and he can also come back to it later if needed. From the photo it appears to be what I call a “PK” or “mag nail”.

The coordinate system is what we call “assumed coordinates”. They are based on nothing other than a random starting point and are normally used for a stand alone survey that is not tied to any defined reference system. Years ago this was the norm. State plane coordinate systems have been around for a long time but access to the information pre GPS days was difficult, time consuming and expensive for clients. Now in many cases it is almost the push of a button and is many times a requirement by localities that it be included on plats going to record. Municipal GIS systems are tied to state plane coordinate systems and having this info on record plats makes the GIS technicians job much easier

I agree that coordinates to 4 decimal places is overkill, but I have done 4 decimal places for 30+ years! We certainly can’t measure this close with normal survey equipment and practices.

I can ramble on about surveying for days, but will stop here.....

 

[CRLLS]

LEDBET, can you tell us the units of measure?

Considering that we put men on the moon using slide rules that have an accuracy of 3 to 4 significant digits, I think 8 digits in this survey is just a bit of overkill. Don't you?

I could imagine that the "calc" noted in the photo may be that these locations are calculated from an earlier form of survey methods. Especially since there is no elevation mentioned.

(off topic) This discussion makes me wonder about how plats of survey relating to land ownership is handled where there are shifts in the earth's crust after the survey is done. It must create problems and disputes.

 

[Winemaker]

The use of infrared and laser style transits/levels are responsible for the above results. They are not manually/actually measured using a chain. Underground in a coal mine, we placed our stations in the roof, and did check surveys periodically to insure accuracy. We used feet as our units.

 

[LEDBET]

LEDBET, can you tell us the units of measure?



Most likely feet assuming this is from the US. In 30+ years I have only done 3 metric surveys and they were government projects for highways back when they were pushing the metric system.


Considering that we put men on the moon using slide rules that have an accuracy of 3 to 4 significant digits, I think 8 digits in this survey is just a bit of overkill. Don't you?



I agree that 4 points to the right of the decimal is overkill, but it just a default setting on the program used to compute the coordinates must like the float/fix button on a calculator.


I could imagine that the "calc" noted in the photo may be that these locations are calculated from an earlier form of survey methods. Especially since there is no elevation mentioned.


most likely this means they are computed coordinate points that were derived from entering a survey plat in the computer. The surveyor entered the metes and bounds (bearing and distances) from the plat to compute the rectangular coordinates of the points so he can load them in his field computer.


(off topic) This discussion makes me wonder about how plats of survey relating to land ownership is handled where there are shifts in the earth's crust after the survey is done. It must create problems and disputes.

Horizontal survey measurements are done in a flat world and elevation changes are not taken into considerations. 1 acre is 43560 square feet measured in a flat plane. When a surveyor measures the distance between two points in the field, the distance is converted from a slope distance to a flat distance for computations. In the old days, we had to do this by hand and need to also record the vertical slope angle of the distance as we measured it. Todays instruments have on board computers that compute the horizontal distance for us automatically. All of this "math" is basic right angle trig.


An acre in the flat desert is the same as an acre on the side of the mountain in a flat plane. If you took the mountain acre and pressed it flat it would be larger!


Land changes due to sudden natural changes are treated differently than land changes that are gradual and due to time in the legal world Whole bunch of laws and statues that deal with that!

 

[LEDBET]

The use of infrared and laser style transits/levels are responsible for the above results. They are not manually/actually measured using a chain. Underground in a coal mine, we placed our stations in the roof, and did check surveys periodically to insure accuracy. We used feet as our units.

This is correct. When I started surveying in the 80's we still used chains (steel tapes) to measure distances. The use of electronic distance measurement was a big time game changer!


I never surveyed in the mines, but know folks that did. You guys have nerves of steel! I don't think I could work underground.