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jp122

How/where should I start a distance and bearings surveying polyline?

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jp122

Hi everybody,

I've been reading tutorials about entering surveyor data, but still there is something I don't get it.

 

Let's say I want to draw this scan in autocad (I already know how to enter relative xy/polar coordinates).

bpstart_zpspppcpwwz.jpg

I guess I should start the polyline at point named 1 and then enter @134.09

 

Segment 1-2 is visible less than 90º north, but even if I draw a visual aproximation angle for 1-2 to start de drawing, how would I then add the second segment 2-3 with the new bearing respect 1-2? How would I get a true to scan polygone?

 

I will be gratefull of there is any explanation/example. Thanks. Paul

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eldon

I wonder where you got that scan from. It does not look as if a surveyor drew it, but someone who knows nothing about surveying.

 

To start with, you would have to have the coordinates of two points. Usually, one measures the angle at point 2, by looking at point 1 first, zeroing the angle and then looking at point 3 next. Angles on a theodolite usually are graduated in a clockwise direction, but the angles on your diagram seem to be anticlockwise angles at each point. How very contrary.

 

But you have to know either the whole circle bearing of the first leg, or the coordinates of two points.

 

You could always take a guess at the first bearing, and then the diagram would be relative to that.

 

You have not got enough information.

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ReMark

You do not have any bearings. You have angles and distances so theoretically it would be possible to draw the property assuming you have the full survey. To orient it correctly though you would have to know which way North is.

 

A bearing would state the direction and list the degrees, minutes and seconds.

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Dana W

When drawing out a boundary survey, there is a Legal Description per the deed, and that is what the surveyor is out there to confirm. They start out at a known point, usually a point coinciding with another boundary corner. The lines are described from the start by bearing and distance to the next point until it comes around and closes on the starting point.

 

If you are using survey coordinates there will be a first point.

 

AutoCad doesn't give a hoot which point you start on. as long as you get them all in you can start anywhere if you know which way your north is.

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RobDraw

As others have already said, if you have the rest of the plot, you can draw the shape. It can be drawn at any orientation until that can be determined.

 

I'm fairly certain there is a way to enter the angle and length so that the angle of the line is relative to the last one. A quick search did not reveal that procedure for me. In the time, it took me to search and type this post, I could have drawn it using the line and the rotate commands and it's been well over a decade since I had to draw a property line.

 

The problem I've had in the past with plot plans like this is that they hardly ever end with a closed property line, most likely due to rounding or some measuring error.

Edited by RobDraw

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ReMark

An approximation of the orientation of line 1-2 could be ascertained by using the IMAGEATTACH command to bring the survey into AutoCAD and tracing over it. That would at least get you started.

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ReMark

Disclaimer: This was done very quickly and in units (metric > meters) that I don't normally work in. The red line was drawn using the method I described earlier. Some angles are defined using reciprocals. Drawing saved in 2010 file format.

 

I think it is correct but I make no guarantee.

 

SurveyBoundaryPartial.dwg

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eldon
Disclaimer: .....I think it is correct but I make no guarantee.

 

[ATTACH]53915[/ATTACH]

 

I read the angle at Point 53 as 75° 13', but otherwise excellent.

 

You are a tease using some reciprocal angles. Making sure one's mental arithmetic is up to scratch.

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ReMark

I rushed it so in all probability I could have easily typed in a wrong angle, even a wrong distance. Thanks for checking.

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Dana W

Surveys in the US don't use relative angles to the last line. They use 90 deg in each quadrant, relative to the North and South cardinal points.

The bearings will be for instance, N 31d 23' 10" West 350.00', which is Go Northish, but veer 31 degrees, 23 minutes, and 10 seconds to the west for 350 feet, with North being zero deg. If the bearing were to the east, the only difference would be East instead of West. Rather than put out 90d West or 00d North, the bearing will be written out as Due West, or Due North, and so on.

 

And yes, the likelihood of any survey closing within say 0.25 feet is pretty remote. The older the survey, thus the simpler and less accurate the science and the instruments used, the more likely there will be found significant errors. It also depends on how long the rod man can stand hearing "Up a tenth" "Back a tenth" "Up a tenth" "Back a tenth" "Up a tenth" "Back a tenth" "Up a tenth" "Back a tenth" "Up a tenth" "Back a tenth".

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BIGAL
closing within say 0.25 feet is pretty remote

 

Had a chat to our fully licensed surveyor, the tolerance of the closure really depends on what is being surveyed, if the surveyor was to do say a 10km road travis and miss by 0.25' 100mm he would be very happy, if he went out and measured a house allotment 4 corners and got the same misclose then he will be trying to figure what has happened and in the case here in AUS he would submit to the surveyors board field notes illustrating why possibly the Title needs to be adjusted. The common pratice here is a 50mm woooden peg with a nail at the actual title point so it can be a few mm off centre.

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ReMark

I think the OP lost interest or moved on to something more important.

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Dana W
Had a chat to our fully licensed surveyor, the tolerance of the closure really depends on what is being surveyed, if the surveyor was to do say a 10km road travis and miss by 0.25' 100mm he would be very happy, if he went out and measured a house allotment 4 corners and got the same misclose then he will be trying to figure what has happened and in the case here in AUS he would submit to the surveyors board field notes illustrating why possibly the Title needs to be adjusted. The common pratice here is a 50mm woooden peg with a nail at the actual title point so it can be a few mm off centre.
Here in the US, neighbors will move fresh hubs, or stakes depending on the purpose, as we call the wooden pegs with a nail, if they come out back and find out their blackberry bush is in your yard after all.:lol:

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Dana W

I worked with one original, unchanged legal description on a deed from 1871, being staked out due to a new fence, with one corner called out as Center of Stump. No sign of stump or marker anywhere near, but it has a pipe (rebar) marker now because it had a distance and bearing to where the stump used to be. It was 27 acres with eleven boundary lines and only missed closing by 0.120 feet

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jp122

wow, a lightning fast answer!

Thanks to you all!

The scan is part of the legal deed of the property and it is done by a professional according to the law and the council controlling their profession, and my opinion is the same as yours, I don't have any degree, but just by watching the drawing, it seems obvious to me that the methods they use to locate a property could be much better. It seems like if the same profession would use diffent techniques on different countries. I've seen several local deeds and all are like this one, some CW others CCW, they sometimes mention the magnetic declination, which in this area is neglectable but nothing, no geographic coordinates and no deviation from north. The compass is drawn on the paper, so north is 90º, it would have been nice the man wrote somewhere the north angle on the first segment, but anyway, I'll survive.

 

It became clear now that I do not have any bearing, I got confused on the translation and at first I thought the meaning of the word applied to my drawing.

 

Special thanks to ReMark for providing me the draft. I'll keep drawing from that one until complete the whole perimeter. It doesn't matter If it doesn't close at the end, it's just to have a digital file to sneak at. The deed attachement, thou primitive, is the one which is the true one according to the law.

 

Thanks. Paul.

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eldon

Apologies for my initial disparaging remarks, but you were presenting a survey with a convention, hitherto unknown to the wider world. Someone has re-invented the wheel, with academian tones and no acknowledgement of conventional surveying practices. The figure does have a certain logic to it and is consistent. It just needed someone to think it out.

 

Personally, I would draw that figure line by line, and convert it into a polyline at the end.

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