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

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

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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<WHAT??. The drawing is giving the bearings respect the previous line (which I haven't drawn yet), I see no way I could know what is the rotacion respect to zero of the first segment I need to draw...

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

2. 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.

3. 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.

4. 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.

5. 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.

6. 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.

7. 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

8. Originally Posted by ReMark
Disclaimer: .....I think it is correct but I make no guarantee.

Attachment 53915
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.

9. 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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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".