Topic: Site property line layout?

[vinnyg]

Hi all,

Hey, I'm not into Civil Engineering at all but once in a while I have to layout property
lines for a project site. The few times I have had to layout a site plan, I have run into
problems getting the property lines to close.....in fact some of the lines will go in the
opposite direction they were intended to go after typing in the distance and bearings
per a particular survey. And sometimes the lines will go in a different direction. The following
is how I set up my drawing and the command I use:

1. Type units
2. Set units to engineering
3. Number of digits to right of decimal  =  (4)
4. Use surveyors units (N45D18'34"W)
5. Number of fractional places for display of angles  =  (4)
6. Direction for angle  =  E   (3 o'clock)
7. Angles measured clockwise?   (N)

(command)  Line
Pick start point
type  @230'<N84D22'05"W

I have used this in the past without problems, but now seems as if dosen't work anymore

I'm using R14

Any thoughts on this??


vinny

[mjfarrell]

Vinny the challenge is that sometimes the bearings on the site lines are annotated to match a legal description.
And thus sometimes you draw a bearing that is labeled N 89 56 32 W, however the line is actually needing to be drawn SE.
Keep in mind the 1st quadrant is NE bearings, up and to the right, however should your line be needing to go down and to the left, you will need to enter that same bearing as SW to get the line going in the proper direction.

[Greg B]

Vinny the challenge is that sometimes the bearings on the site lines are annotated to match a legal description.
And thus sometimes you draw a bearing that is labeled N 89 56 32 W, however the line is actually needing to be drawn SE.
Keep in mind the 1st quadrant is NE bearings, up and to the right, however should your line be needing to go down and to the left, you will need to enter that same bearing as SW to get the line going in the proper direction.

This is one of the best explanations that I read so far!  Thank you!


BTW - I have yet to find surveyors coordinates that close, spot on!

[mjfarrell]

Thanks you sir, that would be the benefit of four semesters of Plane Surveying and several years actually working on field crews.

[alanjt]

BTW - I have yet to find surveyors coordinates that close, spot on!

i feel your pain there (i plotted 8 legals from a surveyor for a limited partition and not one of them closed - that's just crappy workmanship and not checking your legals after writing them), but i can't say that i've never come across surveyor's noting being able to close.

[Dinosaur]

BTW - I have yet to find surveyors coordinates that close, spot on!

i feel your pain there (i plotted 8 legals from a surveyor for a limited partition and not one of them closed - that's just crappy workmanship and not checking your legals after writing them), but i can't say that i've never come across surveyor's noting being able to close.

Not exactly true . . . rounding errors that are not a factor in a small part or a building WILL show up mathematically on a survey where lengths may span a half mile or more. . . unless you are talking a relative large number say in the range of 2/100 of a foot bust on a small lot survey.  Surveyors must FIRST measure the distance and angle measurements between any existing corners - modern survey methods measure these plus or minus 0.005 feet and within 1/2 second and there can be significant accumulated error within these tolerances.  Given the distances involved, this precision is not really visible in most cases.  A legal survey will almost certainly have this rounding error accumulate through the boundary courses.  Often a closure report is required to document that the accumulated error falls within legal requirements.

[CADaver]

(command)  Line
Pick start point
type  @230'<N84D22'05"W

I have used this in the past without problems, but now seems as if dosen't work anymore

What "exactly" didn't work?  The above sequence "worked" in my R9, R2002, and R2008, in that it drew a line 230' long at that angle.

[vinnyg]

CADaver,

What I mean is when I start a property line at a given point where two lines of the
enclosed property come together and after typing the distance and bearing in sometimes
the line will go in the opposite direction that it is supposed to go and when I type in the
next distance and bearing, it will probably not go in the direction it should according to
the surveyor's plot that I am using. Make sense?

vinny

[CADaver]

CADaver,

What I mean is when I start a property line at a given point where two lines of the
enclosed property come together and after typing the distance and bearing in sometimes
the line will go in the opposite direction that it is supposed to go and when I type in the
next distance and bearing, it will probably not go in the direction it should according to
the surveyor's plot that I am using. Make sense?

vinny

Depending on the state you're in, and a dozen other factors, see Michael Farrel's reply.  What you're seeing is a difference between a "Legal Description" and a "Survey Plat".  The "Legal Description" "should" proceed in an orderly fashion to "close" a circuit, (usually in a counter-clockwise direction.)  The Plat can be quite a different story, depending on where you are.

Here in Texas, the existing plats often determine the "direction" of the annotation of subsequent plats. Where a particular description on the plat may start in a comfortable counter-clockwise direction it may abruptly change "orientations" because it shares a leg with a previous plat that is already described by a different "orientation".  Sometimes, depending on where you are, the plat line will fall on a pre-described section line and will assume the description of the section line.  And sometimes it seems that the recording surveyor might have had a "liquid" lunch prior to completing his task.

I usually find it best to sit down with the plat/description and roughly hand sketch it making sure the directions form a circuit.

[vinnyg]

CADaver,

Thanks for the info. It just sometimes I don't have a "legal description" and a
"surveyor's Plat" at the same time to go by. Usually I only have a "plat". But the
info about laying out the lines in a counterclockwise direction will probably help me
in the future. Thanks

vinny

[cgrob]

once in a while I have to layout property lines for a project site. The few times I have had to layout a site plan, I have run into problems getting the property lines to close...

sometimes I don't have a "legal description" and a "surveyor's Plat" at the same time to go by. Usually I only have a "plat"

I don't know what your drawings are used for, but you are treading on dangerous ground if you are not working under a licensed surveyor. Simply showing a dimension from a property line to an existing building is illegal in the state where I live unless prepared under a surveyors supervision.

Where did the plat come from? How do you know if it is right? Without the legal description, and knowing how to interpret the description, you cannot verify the plat.

Has the property been surveyed, position of monuments determined, compared to record, and any discrepancies been resolved? If you go forward with design, you might get an unwelcome surprise when it comes time to build and the lot is really smaller than you thought...


modern survey methods measure these plus or minus 0.005 feet and [angles] within 1/2 second and there can be significant accumulated error within these tolerances

Modern survey instruments can indeed be this accurate, but the rodman (and instrument man) is not. You cannot hold a prism pole perfectly vertical, a good rodman can consistently hold the rod over a point to within 0.02 feet horizontal accuracy under good conditions, 0.005 feet is simply not realistic.

The errors in general do not accumulate, they are random unless you have a systematic error in the measuring instruments.

For instance, draw a line on a piece of paper.
Now measure it with a scale that has very fine gradations, like 1"=80' engineer scale.
Record the distance. Repeat measuring, say 100 times.
Sometimes you measure too short, sometimes too long. If you average all the measurements, you are closer to the true measure of the line, not farther. The random errors don't add up, they tend to cancel out.

A legal survey will almost certainly have this rounding error accumulate through the boundary courses

The mathematical closure of a parcel is calculated in the office, not measured in the field. The parcel should close within tolerance, or whoever is checking the description before recording is not paying enough attention. If you find a description which does not close, it should be brought to the attention of the surveyor to resolve what should be done.

(I work as a surveying technician)

C. Roberts

[vinnyg]

cgrob,

 I don't want you to misunderstand me. Usually I have a "Surveyors's Plat" to go by. I just sometimes don't
have a "legal description" to go along with it. Most of the time I am receiving the information from a third
party instead of from the Surveyor. And most often I am only doing preliminary "Architectural Site
Plans" and would never send anything out without a stamped plat from a licensed surveyor. Thanks for
your comments.

vinny

[Josh Nieman]

Providing a dimension from site property line to building isn't illegal in Louisiana.  It's common site plan practice.  Doing the actual stake-out has to be done by a LS, but providing design of easements, setbacks, etc is well within the range of a civil engineer in the states we work in.

[cgrob]

Maybe I'm just being too cautious, but where I work (California) everyone seems to want a McMansion, and they build right up to the setback limits so there is no room to wiggle.

Recently we were ready to stake a house, got the architect plans, drew the building footprint. Doesn't fit within setbacks. Called the architect, turns out they were using the property assessors map for the lot dimensions. Let's just say there was a lot of last minute running around to address the issues - of course the building crew was on site ready to start, they had to wait until it got straightened out.

So then the finger pointing starts, somehow we got less than our contracted fee even though we did everything right.

Oh well that's life I guess.

C. Roberts

[cgrob]

Providing a dimension from site property line to building isn't illegal in Louisiana.  It's common site plan practice.

Note that above I wrote "dimension ... to an existing building".

Showing a dimension to a proposed bldg. is no problem for site design.

C. Roberts