How would it have best been done in the "Old Days"?

>
> MY QUESTION: Using only a compass, (and SEQUENTIALLY DESCRIBED) how would you best establish a magnetic "cardinal) baseline to be set/used in "zeroing" the TS20's microscope's horizontal vernier,.....WITHOUT.....holding the compass close enough to the supremely magnetic "bearing distorting" effect I assume that the instrument's mass of metal represents? Maybe it's an all aluminum & my intuitions are of a "No blood - No foul" kind of nature! I don't know.
>
How about using ONLY the instrument itself, and a pretty good watch? No compass needed.

Shoot Polaris with it. Probably get a better azimuth than with a compass, even if it's a supremely accurate compass. What latitude are you at?

Rubey, Lommel, and Todd is worth reading, but I much prefer Davis, Foote, and Kelly for the "how it used to be done" as they seem to give better explanations and examples.

For more modern info, Wolf & Ghilani (not necessarily latest edition) is good.

To see how much a compass is affected, just set it up with no metal nearby and then try holding different objects near to see how much it moves. I found that I couldn't wear my glasses when reading a compass because of their steel frames. Most frustrating. Your cell phone will be worse. The batteries in a flashlight to read the compass in poor light will ruin the reading. Etc.

Your procedure seems like a good way to set points on a magnetic bearing. I'm not sure why you want a magnetic bearing.

People often don't worry about setting the instrument to read zero on a known line. You can just read angles and calculate the azimuths in the office. This is especially so if you are trying to squeeze the ultimate accuracy out of your instrument by taking averages, since (at least for older instruments) you benefit from using different parts of the horizontal circle for the multiple readings.

For a geodetic bearing in the Northern hemisphere, Polaris is the easiest way to get decent accuracy. This will be much better than a compass with declination correction. With modest time accuracy Polaris should be able to get an azimuth near the angular accuracy of your instrument. The question from rfc about latitude is because it gets hard to see through the instrument if you are much above 40 degrees latitude and don't have right-angle eyepiece.

The following link THE ADVANTAGES OF POLARIS OBSERVATIONS IN LAND SURVEYING by Robert Fink and Jerry L. Wahl, Branch of Cadastral Surveys, Bureau of Land Management may be helpful. Some of the references to calculators may be a bit cryptic. The 41C mentioned was a popular programmable calculator with a number of plugin chips containing surveying programs.

Another resource you may find helpful is the Star Shots and Ephemeris Data page on the Land Surveyors Reference Page website. Jerry Wahl is again the original source of the information and the page includes links to computer programs that may be of help.

Gentlemen - Thank you for intellectual generosity!

PARAPHRASED FROM BILL93:.. "Your procedure seems reasonable... But,... Not sure why you'd want to"..glaringly illuminates my nascent survey skill set/awareness.

MY TASK: Using my parcel map (with a North PL shown as being 2632' S89.33.17 relative from a PLS - POB hub I found), and, efforting
to place my buildings on my own 45 acres of vacant land in compliance with the County's 25'min property line offset,... I knew I wasn't going to be professionally skilled.

Because of that (and, given the prevailing land topo & having an excess of land to work with), I decided to self set/locate the buildings 100' from the north PL line.

I only had the one PLS pin shown on my parcel map as guidance. I deduced the N PL / S89.33.17W was True North magnetic nomenclature" & meant the line was found by facing S then turning that many (True North degrees) to the W.

Knowing I had factored in a 400% cushion for County compliance error, I determined to just shoot that PL parcel bearing (with the applicable mag correction for Declination),and, assumed that would approximate the True North orientation I thought all survey histrionics are based upon.

I now am being led to deduce: A) I needed more than one start orientation pin to zero my instrument vernier to/from,.. and B) the PL nomenclature doesn’t mean/indicate a True North orientation. It's an expression of angular relativity to/from a known line the legal description is "start-zero'd" from.

I'll keep reading / learning. I enjoy the intellectual trip as much as just being "baby - bird" gifted possession of the destination.

Every off-hand comment you guys liberate in my general direction is appreciated.

When working off a plat, the first thing to look for is a "basis of bearings" statement. These are not always as clear and well-defined as they should be, but will give you some idea how the surveyor oriented his map.

The main options are
-magnetic (very old work),
-geodetic (perhaps derived from GPS or Polaris for one line on the plat),
-matching what a prior plat gave on a line they have in common,
-grid bearing on a projection (such as state plane coordinates) for one line on the plat

For precise work, the convergence angle due will come into play, but that can be ignored for your size parcel at the precision you will be working. You can read about it, but basically convergence angle recognizes that two north lines, from points at different longitudes, are not parallel.

The best way to establish orientation from the plat is to use your best guess as to the meaning of that bearing to go look for another corner monument, and use the plat bearing of that line as your basis for further work.

Ahh, the plot thickens!!

Are you aware that the magnetic north pole moves? This means if the description is based on magnetic north you would need to know both the declination at the time of the original survey and the declination now. The National Geodetic Survey Historical Declination Viewer will give you a rough idea of the change over time. I taught this and most of my students got the calculation wrong the first time they tried to solve a problem. In addition this is only an estimate that local conditions may alter.

If the description clearly states a "True North" or true bearing basis the Polaris observation would serve you better. Your statement that finding two monuments will provide you a better starting basis is also correct. However, once two monuments are found how will you verify that the monuments (stones, iron pins/pipes, trees or concrete monuments) are the points called for in your deed. Confirming this requires measurement to determine the distance between the points is nominally the same as the that reported in the deed.

Also since you are planning on building you should be sure that the deed for the adjoining property does not conflict with your deed or the apparent lines of occupation. There have been numerous posts here regarding property owners building without a survey or ignoring the results of a survey. Since you are asking for an education on surveying I suggest it should include these posts. I hope they help you understand your need for a professional surveyor.

• ... [msg=298972]Ring ring whoopsie[/msg]
• ... [msg=290131]When do you kick over an apple cart?[/msg] Not all "record documents" are to be trusted.
• ... [msg=293974]Wrong lot fiasco revisited[/msg] please read the "article" link in the first post.
• ... [msg=76999]adjoiners, occupation, fences, lines.[/msg] Why a surveyor will take longer than you think is necessary to get an answer that can be defended.

EDIT:
Your notation of the bearing "S89.33.17W" implies you are treating this as decimal degrees. The bearing S89°33'17"W would be read as South 89 degrees 33 minutes 17 seconds West. Minutes and seconds of angle are base 60 similar to expression of time. This is a common error of non-surveyors and can induce significant error on long lines.

After noticing how mag distortion affected trying to use my compass, I searched the West side PL line, & found a "surveyor/hung" piece of duct tape. I setup my instrument & shot 2632' back to the only other point I had, (that being the highway PLS bench mark). My intent was to set two intermediate stakes to measure house offset from.

MY QUESTION: My survey primer later declared 300' a preferred max sight distance. It also said a equational error calc tool for refraction/earth curvature was: (100'- units of distance squared) then multipled by .0002.

That yields a .13 "unknown how it applies" error ecoefficient. Only if offering enlightenment is casually efforted, what/how does that calculation mean/affect placement accuracy of my two intermediate PL line stakes set from a 2632' backsight?

As always, thank you.

For clarity, this parcel map I am entertaining myself with was part of my closing docs & done by a fully professional PLS. All four corners of my land plat map are marked.

This is purely an educational exercise & free of legal risk.

You don't have things sorted out yet in your reading. The 300 ft max sight distance and discussion of curvature and refraction are in the chapter on leveling, and do not apply to horizontal angles/bearings.

Also, I wouldn't be so sure I'd found another corner, if all I saw was a piece of duct tape. Surveyors don't usually use duct tape. They do use a thin plastic ribbon to call attention to monuments, but the ribbon isn't the monument.

Does that plat contain a title similar to "Mortgage Loan Inspection" (MLI) or "Mortgage Location Survey" (MLS) and a statement that advises the plat should not be used for boundary determination or development of the property? Many states have standards allowing this type of document to be produced. The requirements for accuracy of the field work and the resulting document are less than for a boundary survey. In some cases there is no requirement to check for conflicts with adjoining deeds. Mortgage surveys should never be used for what you are proposing!!

The purpose of these is to inform the lending and title agencies of any preexisting conditions that would make resale of the property difficult. These are intended to detect buildings, sidewalks or driveways on the wrong property. Simply if the borrower defaults on the loan will the lender be able to sell the property quickly.

REGARDING THE LEGAL PROBITY OF MY EFFORT TO LEARN SURVEY SKILLS:

This +/- 45 acres is a " straight / 4 line" parcel. All 10 of my +/- 35 acre - parcel neighbors (on a 1 square mile map) are on the same parcel map / under one PLS stamped signature.

My lot is a 726' x 2632 rectangle. I'm willing to be wrong, but, if I've identified the 4 corners, it seems like my only serious possible error is in shooting 2632' on one single backsight.

If I hear from this list that my error probability is at or even modestly close to a 100' of error likely consequent from that corner to corner backsight, I will then take your graciously offered "hire a professional surveyor" counsel.

County gives me a 25' min offset. The house will set in the center/350' from both N&S property lines. I have planned for a future barn @ 100' from the N line.

Even with my 2632' "single" backsight, it seems like like I should have ample cushion.

Have I reasoned clearly?

Your "duct point" is taken. I didn't make a declarative note that there was a PLS marker underneath the duct tape I found , BUT, NOTABLY, the number on it didn't match the PLS number on the parcel map. I wrote that off your being a "typo".

Straightening it out is easy! The PLS who signed the recorded map is my neighbor. His wife was the real estate broker in the/our transaction

That said, I will call him & have him clear up that ambiguity.

Thank you gentlemen!

> REGARDING THE LEGAL PROBITY OF MY EFFORT TO LEARN SURVEY SKILLS:
>
> This +/- 45 acres is a " straight / 4 line" parcel. All 10 of my +/- 35 acre - parcel neighbors (on a 1 square mile map) are on the same parcel map / under one PLS stamped signature.
>
> My lot is a 726' x 2632 rectangle. I'm willing to be wrong, but, if I've identified the 4 corners, it seems like my only serious possible error is in shooting 2632' on one single backsight.
>
> If I hear from this list that my error probability is at or even modestly close to a 100' of error likely consequent from that corner to corner backsight, I will then take your graciously offered "hire a professional surveyor" counsel.
>
> County gives me a 25' min offset. The house will set in the center/350' from both N&S property lines. I have planned for a future barn @ 100' from the N line.
>
> Even with my 2632' "single" backsight, it seems like like I should have ample cushion.
>
> Have I reasoned clearly?

Your reasoning is correct if you are absolutely sure you have the correct corners. There are two questions you need to answer. First are your rear corners common with the adjoining properties behind you? It is common to find offset corners, from a few feet to 150 or more, along a common rear line. On a map showing a full section (one mile square) offsets may be difficult to detect. Such maps are often drafted at a scale of one inch equals four hundred feet or one inch equals 660 feet. At one inch equals 660 feet a 50 foot offset between two corners on the same line is approximately 1/16 of an inch. Nearly undetectable unless dimensioned on the map. Using the wrong, 50 foot off for example, corner in the field could result in a 25 foot error at 1320 +/- depth from the front line.

Second even if you know there is another corner how do you verify you have the correct corner. Common practice is measuring two distances along the side and back of the property. Then measuring the angle between the two distances verified is the best course. In my home state a 2632 foot distance should check at +/- 0.26 feet (approximately 3 inches) to be within current standards. I would hope to check at less than one third of that.

Given all of this please be aware that surveying without a license is illegal in all states and a professional surveyor assisting or facilitating such activity is subject to disciplinary action. Working within your own property, construction staking, may be legal in your state. Determining your common boundary with your neighbors, depending on state law, may not be legal. I would be more comfortable with the surveyor that completed the survey showing you your corners in the field and discussing the surveying laws of your state.

Dallas - the parcel map shows the pl bearing as having decimals, which in mind mind means just that. Can you concur with that assumption?

Wouldn't the map maker have used dd/mm/ss notation were that his intent?

Where are you located? I'd be a little suspicious of any survey plat in the US that used the punctuation 2632' S89.33.17W because that would be quite uncommon among licensed surveyors. When I saw it in an earlier post, I took that to be your shorthand. Is that really the punctuation in the document?

It is titled :

ALTA/ASCM LAND TITLE SURVEY
-FOR-
"insert here the property seller's name"

ADJACENT TO THE PLS's SIGNATURE IS THIS PARAPHRASED CERTIFICATION:
**Blah!.. Blah.!.. PLS's name certifies to (insert the names of two title companies here) a land survey was done.. Blah! Blah! **

Two different sentences declare: the bearings are relative to a highly specifically called from a numbered section,... AND,... that it was..."based upon the existing monuments show on the map above",....!

And, I was wrong about the line nomenclature on the map is in dd/mm/ss format.

And, Bill93 said that the refraction/curvature error calc equation applied only to the survey leveling module of affairs.... If that's the case, AND, I could see the highway's PLS numbered monument that I got from my half mile sight,....what error (if any at all) does that long a sight introduce?

Thank you ever so much!

Bill.... That was just my paraphrasing. I am outside of Colorado Springs.

The bearings are written as N 89°33'17" E. Below the line is the distance 2633.40'.

Separately, please, can you assure me this isn't spinning out of a casual realm of affairs. I can't see how standing on my own land looking through my own theodolite, to locate my own buildings is somehow reasonably considered surveying without a license. I'm not understand that. Is it hard to reset that social "gyro" for me?

I understand.... I didn't know that my questions would create conflict or tension for you.

I have generously learned from you commentary.

Thank you.

What I need to do is see if one of these local surveyors could use a 58 years young "grunt" so the medium of texting on the phone isn't creating a barrier to effective communication.