discussion of significant figures

I'm not sure that significant figures are as important as court interpretations. I believe there are a significant number of court rulings that say something in a deed should be taken literally unless you can show a clear mistake.

As an example, let's say a lot was created to encompass an existing building and the lot was supposed to be 90 X 100. But lo and behold the building is really 91 feet wide. I think the intent would trump the number regardless of how many significant digits were used.

But if it was a vacant lot in the middle of no where, then 90 X 100 would be what matters.

discussion of significant figures (or is it precision?)

My guess is precision.

discussion of significant figures (or is it precision?)

Yes, facts on the ground do change the matter. and yes Vern it is a question of precision. I have no way of knowing by the terms of the deed that 94 feet is intended to be equal to 94.00 feet. I just wonder what others think and if there is a reference that I may cite...

discussion of significant figures (or is it precision?)

In that case, I would choose the precision I was most comfortable with and convert all dimensions to that precision. Either that or survey the property.

or is it accuracy?

I agree either way, the least precise or accurate should control. Truncate them all to the nearest foot and put a +- next to them. Bet they're going to love that:whistle:

94.00' (Record distance 94')

Thanks Spledeus...good idea but in this case I want to make a different statement. The one I want to make is "94' record and measured."

> I am looking for reference material that discusses the proper notation with respect to significant figures. I have retraced many descriptions where dimensions are called as i.e. 94 feet, 6 feet and 8 inches, 34 feet and 7 and 3 quarters of an inches, in the same description. Generally these descriptions have right angles and are rectangular in nature. It seems to me, that as stated in the original deed all these dimensions are of a different precision. I have recently received comments for a new lot meager description that my new description needs to state the same precision for each distance. So 94 feet would be show as 94.00 feet.

My observation would be that many surveyors in the late 19th and first half of the 20th century truncated a distance that was measured as 94.00 ft. to 94 ft. when the map was prepared. 94.10 ft. became 94.1 ft. and 94.05 ft. was written as 94.05 ft. This suggests to a modern eye a difference in the precision of the measurements when none was apparently originally intended. The truncation of distances was just for compactness on a map.

As I recall, this same convention is still followed in some states in Australia. I may be misremembering this detail, but I think it was Queensland where truncation was expected.

In modern US practice, I'd prefer to see 94.00 ft. for the purposes of clarity unless the truncation rule followed is explicitly stated on a map.

> I am looking for reference material that discusses the proper notation with respect to significant figures. I have retraced many descriptions where dimensions are called as i.e. 94 feet, 6 feet and 8 inches, 34 feet and 7 and 3 quarters of an inches, in the same description. Generally these descriptions have right angles and are rectangular in nature. It seems to me, that as stated in the original deed all these dimensions are of a different precision. I have recently received comments for a new lot meager description that my new description needs to state the same precision for each distance. So 94 feet would be show as 94.00 feet.
>
>
> Thanks for your help

In significant figures, 94 feet is only to the nearest foot. The scrivener may have dropped the trailing zeros if they weren't aware of the "rule" but I would suggest that you can't state that the written significant figure was any better than what is written. I like Buckner's write-up on significant figures (Survey Measurements and Their Analysis by R.B. Buckner).

I don't know about legal citations, but I think it's a matter of mathematical sig. figs.

Generally speaking, you measurements are as strong as the weakest value, so if one of the measurements in a dimension of a parcel is 94 feet, I would consider that a multiplicative precision of two places. I would keep the same figures as the deed description with the weaker and stronger figures. I would consider 34 feet, 07&3/4 inches around three places behind the foot 34.646 feet. and I would consider 6 feet 8 inches to be (08/12) as two places.6.67

I would consider writing my values to the nearest 0.01' except when the deeded values are less precise than that.

those are just my immediate thoughts.

Tom, you express my thoughts exactly. Kent I have heard your comment before and it makes sense. In this case, I am looking at a deed description and not a map where graphic presentation is a consideration.

>
> My observation would be that many surveyors in the late 19th and first half of the 20th century truncated a distance that was measured as 94.00 ft. to 94 ft. when the map was prepared. 94.10 ft. became 94.1 ft. and 94.05 ft. was written as 94.05 ft. This suggests to a modern eye a difference in the precision of the measurements when none was apparently originally intended. The truncation of distances was just for compactness on a map.
>
> As I recall, this same convention is still followed in some states in Australia. I may be misremembering this detail, but I think it was Queensland where truncation was expected.
>
> In modern US practice, I'd prefer to see 94.00 ft. for the purposes of clarity unless the truncation rule followed is explicitly stated on a map.

we have no requirement for truncation of dimensions shown on plans here Kent, but i think you may mean trailing zeros, and they are not to be shown in New South Wales. i think occasionally some dimensions look lost in a cluttered plan without trailing zeros.

Dane...

Over 20 years ago, I practiced in CA under the mentorship of a CA PE who practiced for over 45 years in CA. He taught me to never change the original dimension of record. Always show it as in the record and then put you're measurement in whatever significant figures you want. Be consistent but do reference the original record measurement as recorded.

Mi dos centavos

Pablo B-)

> we have no requirement for truncation of dimensions shown on plans here Kent, but i think you may mean trailing zeros, and they are not to be shown in New South Wales.

Yes. I was thinking of some plan requirements I'd read, but recalling them as pertaining to QLD when they were probably NSW.

Thanks Pablo.

> so if one of the measurements in a dimension of a parcel is 94 feet, I would consider that a multiplicative precision of two places. I would keep the same figures as the deed description with the weaker and stronger figures. I would consider 34 feet, 07&3/4 inches around three two places behind the foot 34.646 .45 feet. and I would consider 6 feet 8 inches to be (08/12) as two one places.6.67

My significant figures were wrong. the nearest inch would be more equivalent to one place behind the decimal, not two. 3/4 of an inch would be to the hundredth.

but my point is moot, just wanted to correct my post. I agree with Pablo if I understood correctly. Why not just keep the exact same figures as on the original deed?

> I have recently received comments for a new lot meager description that my new description needs to state the same precision for each distance. So 94 feet would be show as 94.00 feet.
>
>
> Thanks for your help

Seems like every other week, I'm hearing of something nonsensical coming from someone in some position of authority over there, telling you to do things like eliminate potentially pertinent evidence from your RS, reject established monuments in favor of the latest County LSA of the "true" block corner locations (that move with each new set of measurements and each new adjustment), and now to create a level of precision which does not exist in the record information.

Tell them that you can't increase the precision of a measurement without a more complete history of its inception, use, and measurement history to justify reporting to a greater degree of precision, and that doing so without such information would be a violation of Board Rule §476(c)(7) A licensee shall express professional opinions that hav a basis in fact or experience or accepted land surveying principles.

Unless there is one or more facts that demonstrate that 94 feet in this instance is equivalent to 94.00 feet, that's Strike One! (As you've properly stated, other dimensions reported to a greater precision do not have any bearing as to the precision of this dimension unless it can be shown that they come from the same original survey and were made with the same degree of care - a degree of care which supports the precision asked for)

In your experience, you have encountered descriptions which utilize dimensions of varying quality gleaned from various previous record sources. You do not have personal knowledge that all of the dimensions in the instant case are based upon measurements and calculations which support the level of precision asked for. Not only does your experience not support acceding to the request, it precludes doing so as it would be an irresponsible thing to do, making neither scientific nor legal sense. Strike Two!

As anyone who remebers high school physics, the reliance on data is highly dependent upon the significant figures (precision) to which the data is given, and reporting conclusions and reporting intermediate calculations is governed by the significant figures associated with the data that went into them. If you would lose points in a high school class in which no one will be relying on the results of your work, it is easy to understand why it would be exceedingly irresponsible to intentionally commit a sig fig violation in the technical content of a legal document of record, the conteent for which you will be professionally responsible for. A person who not only has had high school physics, but who has completed a B.S. degree with a amjor component being measurement science and mathematics should be on top of this and be educating his review staff to not ask for alterations to data which cannot be responsibly provided. I recall wayyy back to my freshman year in my survey degree during which my instructors drilled it into our heads that sig figs were fundamentally important. If college freshman in a B.S. Surveying Degree program got dinged for sig fig violations, how much more realization of the importance, and how much more awareness of the principle should a licensed surveyor have? The request is not only not based on accepted land surveying principles, it fundamentally violates them. Strike Three!

Please tell me that it's a title officer who is asking for this and not someone who should know better from the office that you've related so many other similar requests/demands have come from.

This thread raises a number of legitimate questions. No, I don't have answers for all the issues but would like to look forward. I am of the opinion that the surveying profession has a lot to offer society - in many cases even more than currently being delivered. There is much more we can do.

If we look forward 10 years, 20 years, or some other number, the quality of spatial data elements (distances, angles, coordinates, etc.) will be given in terms of standard deviations to describe spatial data accuracy. Significant digits and standard deviations are very compatible as the rules of significant digits are based upon measurement and error propagation (you know, statistics).

Getting a handle on standard deviations, network accuracy, local accuracy, and other statistical issues requires effort. Some can adapt at the conceptual level quite readily while others will resort to learning rote rules of application. Both are legitimate. In any case, society deserves our best effort.

Merry Christmas and Happy New Year!

Kent, My Liscad program is set to show on the generated plans a rounded precision distances that is computed from generated and stored data coordinates.
eg the protocol is,

Precision distance of 20.000 metres shown as 20

20.004 20.00

20.005 20.01

20.040 20.04

20.400 20.4

RADU

> Kent, My Liscad program is set to show on the generated plans a rounded precision distances that is computed from generated and stored data coordinates.
> eg the protocol is,

Is that also the convention followed in drafting survey plans in South Australia, Richard?