Just a student type question. Say you have a 40 ac piece, you know one corner pin but no others.You have a good filed map of parcel.
Can you walk into the middle of the piece and establish a random point and from the info you have and a good theodolite, can you find the other 3 corners without using any magnetic bearings, just angles and get it accurate??
yes
and for my next magic trick...
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you need some method of orienting yourself with the lines and directions on the record map... magnetic bearings help, occupation helps, etc.
A theodolite just measures angles
A total station (angles and distances) would be of more use
jim.cox, post: 337175, member: 93 wrote: A total station (angles and distances) would be of more use
Of more use, certainly, but it still won't solve the problem. You have 1 position but no direction, so absent some by-guess-and-by-golly (which any good field surveyor can provide), you have an infinite number of solutions to the problem.
You may find yourself within a stone throw of the next monument.
Compass surveys are usually made by following course and distance along or using an offset method and looking along that area for boundary evidence.
If that course is too difficult to maneuver, then more conventional methods are required where more computations are necessary.
I recon using sport grade handheld GPS.
0.02
You would need a basis of bearings in some form.
If you were using GPS, your basis of bearings would be would be on the chosen projection by default. If your record was known to be on a State Plane basis, you would be in good shape. If your record had an astronomic basis of bearings you could make assumptions that would get you close enough to make searches for the other corners.
When not using GPS you might have to resort to the compass for a provisional basis. Or a sun shot. Or a fence line or road centerline.
I am talking about making assumptions to aid a search for more corners. Permanently establishing 3 corners based on on 1 found is not done.
I'd prefer a hand compass, Suunto, or the like, and either pacing, or a 100' cloth tape, from the local hardware store to try to find the rest of the corners. And, a metal detector. And, a roll of flagging. And, then we would know where more stuff is. Maybe not your corners, but, we would know where more stuff is! 🙂
8p35hg, post: 337172, member: 10401 wrote: Just a student type question. Say you have a 40 ac piece, you know one corner pin but no others.You have a good filed map of parcel.
Can you walk into the middle of the piece and establish a random point and from the info you have and a good theodolite, can you find the other 3 corners without using any magnetic bearings, just angles and get it accurate??
If you can find all the corners - then yes, just about any method used is accurate. If you are worried about the precision of reporting the bearings and distances to the found corners - then no - read the other posts.
with two known points and a known distance between them, you could figure out a lot more with a series of angles-only. But I don't think you could do it from one setup. It would be a cool exercise to figure out how to get around with angles-only. (also, it has been very seldom where I have been able to see all the corners of a 40-acre parcel from one vantage point. Maybe in a cleared farmer's field. If you have a good pace, or can read stadia, that is a way to help you get close for distances as well, but from your description, I don't think you can do what you are suggesting.
8p35hg, post: 337172, member: 10401 wrote: Just a student type question. Say you have a 40 ac piece, you know one corner pin but no others.You have a good filed map of parcel.
Can you walk into the middle of the piece and establish a random point and from the info you have and a good theodolite, can you find the other 3 corners without using any magnetic bearings, just angles and get it accurate??
Being you have a good filed map of parcel. One could set up in the middle of 40 acres. Measure from the one corner pin to the point in the middle, use a compass to get a bearing from the point in the middle to the corner pin, then using the data from the "good filed map of parcel", calculate the direction and distances to the to be found corners. It becomes a trigonometry exercise to calculate the triangles. In fact in a way I do this all the time.
"Permanently establishing 3 corners based on on 1 found is not done"
what i was getting at was by using trig and maybe calculus and a theodolite with an accurate EDM..that you might be able to establish the other 3 corners.But I guess not. The reason I was asking is because I have seen how un precise and even slightly changing using just a compass is.
5 guys will walk to 5 different spots using a compass and declination changes and every compass is more or less accurate depending on price etc.
. But it sounds like if you were putting in 3 new corners you would have to use a magnetic approach
at least somewhat.
Jules J., post: 337214, member: 444 wrote: use a compass to get a bearing
A compass isn't part of "the information you have" in the original question.
Jim Frame, post: 337235, member: 10 wrote: A compass isn't part of "the information you have" in the original question.
That's true.
8p35hg, post: 337229, member: 10401 wrote: "Permanently establishing 3 corners based on on 1 found is not done"
what i was getting at was by using trig and maybe calculus and a theodolite with an accurate EDM..that you might be able to establish the other 3 corners.But I guess not. The reason I was asking is because I have seen how un precise and even slightly changing using just a compass is.
5 guys will walk to 5 different spots using a compass and declination changes and every compass is more or less accurate depending on price etc.
. But it sounds like if you were putting in 3 new corners you would have to use a magnetic approach
at least somewhat.
With a theodolite and an accurate edm (and a compass)....that changes everything. You do need the distance factor. A compass can get you close. Some of those original properties were even set with a compass, in which case a precise bearing doesn't do you any better than a compass bearing. However, with that theodolite, you can get a more precise bearing by solar observation or even more precise with a night stellar observation. In your repainted scenario, you could do what you want.
You are simply going to need more than one monument plus measurements to establish other corners. In the extreme that "more" might not necessarily be other iron corner monuments. But you will need more.
8p35hg, post: 337172, member: 10401 wrote: Just a student type question. Say you have a 40 ac piece, you know one corner pin but no others.You have a good filed map of parcel.
Can you walk into the middle of the piece and establish a random point and from the info you have and a good theodolite, can you find the other 3 corners without using any magnetic bearings, just angles and get it accurate??
Based strictly on the information given, you do not have enough parameters to solve the problem mathematically and certainly not accurately. If you what you mean by accurate is the accurate location of the corners.
8p35hg, post: 337229, member: 10401 wrote: But it sounds like if you were putting in 3 new corners you would have to use a magnetic approach
at least somewhat.
I would suggest that you should establish the location of the 3 "new corners" based on the preponderance of evidence. The math, magnetic bearings, and even the "good filed map" are but a part of what needs to be considered.
ok good info
A long time ago, we did a lot of work with stadia. It was a little crude but it works.
If by "find the other three corners" you mean find the monuments marking those corners, the answer is that it depends...
... were they ever set and do they still exist?
... if they exist, is a portion of each above ground surface or are they entirely buried?
... what physical obstructions are there to finding the monuments? Is there thick vegetation, intervening hills and gulleys, the hulks of old cars comprising portions of a junk yard?
... what material were the original monuments?
... are there other physical indicia to help lead you to the corner monuments?
... are you prepared to dig with your hands or will you take a shovel with you? What about a magnetic locator?
If you are actually talking about the corner locations themselves, you would be better off leaving the theodolite (or total station) in it's box, taking a hand compass, machete, locator, and shovel and using other physical evidence to lead you to the vicinity of each corner, and then look more carefully in each of those immediate vicinities for evidence of the precise corner location in the form of a discrete monument or corner of occupation that may mark the corner.
Either way, once you've found these things, you still won't know if you've found the corners until you are able to analyze all of your boundary facts as a complete body of evidence. There is no way whatsoever that you can find the corners with only knowing one corner location and using just a theodolite (or total station). You may luck out and find something that might mark the corner, but you have no way of knowing until you are able to verify with mutually supporting evidence.