Hello,
I need help with a problem I came across recently and I am hoping you could help me.
I am a farmer and I want to determine the end points of my properties. I have been checking surveying tutorials but nowhere did I find a clear solution to the practical problems I am facing.
What I need is:
How to determine the position of a point X on the open field given the position of the points A,B,C... (church towers, power poles..) are known? I can get a map (with all the points of interest (A,B,C,X) and an old theodolite. The distance between all the points (including X) is a few kilometers.
The problem with the tutorials I found was that they all say I need to place the theodolite on the control points (A,B,C) which in my case can't be done for practical reasons (they are too far away from X and they are unapproachable).
So, what I basically want to know is how to determine the position of X with theodolite placed not on control points but somewhere near X (within reasonable walking distance (say 10-30 meters)). Where do I place the theodolite then?
Thank you in advance.
What you want to do is called resection.
Set up your instrument where you can see all three control points (hopefully you have good geometry) and turn your angles, at least one set face 1 and face 2 to each control point but the more sets the better.
Then calculate your position, you'll have to look up that part.
You'll get a lot of comments about determining your own property corners on this site, because there is more than simple-trigonometry or basic math to get to your true corners.
YOu say you have an old "theodolite". Does that mean you can only measure angles? Do you have a way of measureing any distances? Your problem can get tricky using only angles, especially if you can't set on any of the know points, a,b,c....
Resection... I see.
Thanks Dave, will look up for that. In case I don't manage will come back for more help 🙂
Am good with geometry (have studied electrical engineering) so that shouldn't be a problem.
Yes, only angles, Tom, no distances and no setting up on control points. Can it be done still?
Woooooooooooo boy.... you better put on your asbestos undies... you're gonna get flamed here for sure.
That being said... What is the accuracy of the radio towers, steeples and such? And how are they referenced to your survey? If you're just scaling off of a Google Earth picture or a local set of aerial photos, you are just asking for trouble by staking your own property lines. I've NEVER reverenced a radio tower, steeple, etc. on a plat
over the years, and I've never seen ANY one around here do it either.
You really should employ the services of a local, Licensed Land Surveyor to perform this work. I understand wanting to learn and do it yourself, but you are possibly opening an ugly can of worms here.
> Woooooooooooo boy.... you better put on your asbestos undies... you're gonna get flamed here for sure.
But but but... what did I do? 🙂
>
> That being said... What is the accuracy of the radio towers, steeples and such? >And how are they referenced to your survey?
I don't know what is their accuracy. The are on the map so I want to use them as control points.
>If you're just scaling off of a Google Earth picture or a local set of aerial >photos, you are just asking for trouble by staking your own property lines.
No, I don't use Google Earth. Proper topography maps will I search for.
>I've NEVER reverenced a radio tower, steeple, etc. on a plat
> over the years, and I've never seen ANY one around here do it either.
>
Oh? Don't surveyors use steeples as reference points? I thought they do. How do they do it then?
> You really should employ the services of a local, Licensed Land Surveyor to >perform this work. I understand wanting to learn and do it yourself, but you are >possibly opening an ugly can of worms here.
I have many small scattered fields which might have (or have not) floated by no more than a meter from their original position. So, to prevent trouble I want to bring them back. Licensed Land Surveyor would cost me money which I want to save by bugging the good people on this forum 🙂
Lets just look at things from the purely academic point of view. Can this, what I need, be done under the restrictions I described and if so then how?
I'm not sure what country you are in - obviously not USA if you are thinking in meters. So we don't know what your property laws are. In nearly every location, though you are going to need a professional to actually mark boundaries.
Edit after seeing more replies:
As Carl points out, land surveys are not referenced to sufficient accuracy on any topo maps I've heard of.
Deleted comments about computational methods, which are of interest only as an intellectual exercise in this context.
> > Woooooooooooo boy.... you better put on your asbestos undies... you're gonna get flamed here for sure.
>
> But but but... what did I do? 🙂
You're asking surveyors how to do their profession that is regulated by the state/commonwealth/province that you/they live. Do you practice your own law also?
> > That being said... What is the accuracy of the radio towers, steeples and such? >And how are they referenced to your survey?
> I don't know what is their accuracy. The are on the map so I want to use them as control points.
>
> >If you're just scaling off of a Google Earth picture or a local set of aerial >photos, you are just asking for trouble by staking your own property lines.
> No, I don't use Google Earth. Proper topography maps will I search for.
Boundary surveys and topo maps have very, very little common or are used very rarely together.
> >I've NEVER reverenced a radio tower, steeple, etc. on a plat
> > over the years, and I've never seen ANY one around here do it either.
> >
> Oh? Don't surveyors use steeples as reference points? I thought they do. How do they do it then?
We use boundary markers as called out in the deeds and plats of you and your neighbors.
> > You really should employ the services of a local, Licensed Land Surveyor to >perform this work. I understand wanting to learn and do it yourself, but you are >possibly opening an ugly can of worms here.
>
> I have many small scattered fields which might have (or have not) floated by no more than a meter from their original position. So, to prevent trouble I want to bring them back. Licensed Land Surveyor would cost me money which I want to save by bugging the good people on this forum 🙂
Trust me, you are not going to find people to walk you through how to perform a land survey for free. We're a great group of people, but you're asking an AWFUL lot of us just to save yourself a few bucks....
> Lets just look at things from the purely academic point of view. Can this, what I need, be done under the restrictions I described and if so then how?
I don't think so. It's like your trying to design an home electrical system with a set of house foundation blueprints. They both are of use building a house, but they have completely different and unique uses and are hardly related.
Good luck, you're gonna need it.
Carl
By the way...
Where are you? What country at least?
What you want to do is a 3 point resection, see link.
http://mesamike.org/geocache/GC1B0Q9/tienstra/
Paul in PA
If you really could tie your property corners by coordinates on a City-/County-/State-wide system you might want to try the following:
Go to profsurv.com and click on The Problem Corner.
Problem No. 20 gives a sample of a "Two Point" resection and Problem No. 30 gives several solutions to a "Three Point" resection.
It uses basic geometry, but you have to know how to measure the angles and set it up so you have what is known as strength of figure. Small angles (150°).
I had a warehouse owner ask me last week how to find the width of the "easement" in front of his property, and I finally figured out he meant the right-of-way width. I found the plat and sent him a copy, no charge. Then he asked if he could just split the pavement and come over half the right-of-way width to put in a new fence. That's when I told him that would be a big mistake. He then hired me to do a real survey, which turned out to be exceptionally easy when I found a lead cap that had been there since the 1930s, but the line wasn't anywhere near where he thought it was (the face of the building was on line).
Angles only will simply yield a similar solution.
You will need distance to complete the equation.
This is exactly what I was looking for. Lots of material for me to study now.
Thank you.
Seems like a useful tool.
Thank you.
I think all the distances I need I can measure on the map.
Of course I don't intend to take legal matters in my hands. Like the warehouse owner from Bruce's post I just want to know where I stand before I hire the professional surveyor to do the markings.
I think you will understand why I want to do it myself when I explain you more of the situation here.
This is one of my fields:
https://mapsengine.google.com/map/edit?mid=zvjO3HLqqo9Q.kZ0aBi2ZqQCE
Now you also have the answer where I am from 🙂
As you can see one particular field is bound by roads at its width and by neighbouring fields at its lenght. I think even on google maps you can see that there is no markers between any of the fields (except a few trees here and there). So, my neighbour just continues to plough from the place where I stop ploughing which makes the boundary between me and them very unstable.
In ideal-extreme case I would need one surveying per year for all of my fields so it is natural I want to do it myself.
I think a network of markers do exist there (stones buried in the ground) but in time they were covered up by ploughs. And I think professional surveyors here use to locate them (before they switched to GPS) and then reference their measurements by them. I have no idea how they use to find them. Perhaps it would be better to ask some of them if they are willing to share the secrets of the trade than to deal with the 3-points resurection problem and do lots of calculations on the fields.
North-eastern Serbia.
Three-point resection for boundary is a last resort solution.