“CALCULATED“

[Scott]

This has probably already been discussed in this forum, but I searched and did not find anything specifically related.

Calculated or Measured?

If you lay a chain, or shoot with EDM, or post-process GPS vectors, on a line between two occupied points, it is definitely measured. Everything else shown on the plat (except record distances) would be calculated from measured data as shown.
Is there a difference between the two worth noting?

More and more, I see RTK is being used for Boundary Surveying.
What then is the difference between Calculated and Measured distances?

Over the years, I have unconsciously relegated “calculated” to only record courses that I must use coordinate geometry in conjunction with the data shown on the record map to obtain that which is not specifically shown on the record map.
I no longer differentiate between Calculated or Measured as in the above paragraph, it is all measured for me now.

What do you do and why?

[David Kendall]

Great questions! This is my practice:

Calculated record data is noted for bearings or distances not shown on the record map. Typically this means a cross-tie. I have seen the occasional overzealous map reviewer ask for a calc notation on on overall record lot dimension when two segments are indicated on the record....

For example - the 100' overall dimension is not on the map:

(50') + (50') = (100')calc

On a measured or established line I try to avoid using the calculated note. Measured dimension belongs between two monuments. If nothing is found or set then I prefer not to state a measured bearing and distance mostly because I have seen surveyors use these dimensions later to justify establishing a corner via corner record which I did not intend to establish on my survey. This might be a circumstance where I was establishing three corners of the rectangular parcel but not the fourth. The two monumented lines would indicate measured dimensions and the other two lines indicate record dimensions only.

Occasionally I see the notation "calc'd to close" on a line on a map. This tells me that the surveyor did not formally establish the line in question. I recently added this note to a record dimension where I found a closure error on the map that I was not comfortable perpetuating so I held a different bearing than what was on the map

[dharri]

It is my belief that dimensions determined from measured values represent measured data. Dimensions determined from record dimensions that are calculated from record dimensions should be identified as such.

[Scott]

Yes, me too.

[kwilson]

Almost everyhing we do is calculated. A horizontal distance is calculated from a slope distance and zenith angle.

But it seems your question is when to use what some of us refer to as CFR or calculated from record.

Most map checkers ask me to use CFR when a calculation goes beyond addition or subtraction. Such as us when we find two monuments from a previous survey that are not on the same line but the calc'd bearing and distance between them can be calculated from the measured data on the map. And by measured data we are referring to the official line dimensions that the surveyor has shown on his boundary lines on his map.

I would venture to say that 99.9% of the time i don't set up my gun on one monument and measure to another one. So just about every bearing and distance shown on my survey is calculated somehow but the boundary lines i am showing as "measured" means these are the lines my survey has established or re-established and the dimensions are my official determination.

[Scott]

kwilson: "But it seems your question is when to use what some of us refer to as CFR or calculated from record."

No, I wanted to know if anybody designates lines as "calculated " when the annotation is obtained from measured data.
Like in the old days, the LS would chain only 3 sides of a rectangle, they would designate those 3 sides "measured" and the 4th side "calculated".

It sounds like nobody does anymore.
I do not either. I agree with dharri: "dimensions determined from measured values represent measured data."

[PLS7393]

A good example when I label a dimension as "Calculated" would be when there are found monuments at the beginning and end of a centerline curve shown on a map. When holding the two monuments (potentially as B.O.B.) I calculated the chord bearing and distance.

Other than that it should be obvious the dimensions shown are from record data, or simply your measurements which can be retraced by anyone with minimum competence (addition or subtraction).

In my opinion, too many map checkers these days do not have good experience under a mentor for map checking, and bring their style into my map.
Last time I checked, maps are still my professional opinion, not yours!

As for your comment about RTK for boundary surveys, . . . another opinion of mine would say "garbage in - garbage out".

[CBarrett]

It's either calculated from record maps, or measured and derived from your field measured data.
Distinction is not whether it was measured by actually touching the ground.
divided line is drawn between whether you are using your own measurements (and your own methodology and investigations ensuring field precision and resulting accuracy) or are you relying on someone else's published values.

You could argue that with GPS you are using someone else's published values to start with. This is however comparable to using published coordinates and elevations in pre GPS days.

You are still adding your own level of direct or indirect field measurements arriving at whatever accuracy you are stating (or not stating) on the map. Your values, whether directly measured, indirectly measured or calculated from measurements are subject to YOUR accuracy. Tolerances in numbers Calculated from another's record map are subject to their methodology and resulting accuracy.

Or to explain it a tad differently...
We don't traverse through each monument in every possible direction (which may be used when inversing between them to compare to someone else's map) when we are locating them using methodology that will gives us confidence that when inversing between surveyed values, we are 95% confident that it can actually be measured in the field +/- (whatever your error ellipses are for 95%). We rely on our field methodology to give us this level of certainty.

So if you are placing an accuracy statement on the map, it would not be applicable to any (R) and (CFR) values.
Personally, I am not a huge fan of specifying a (CFR), however, I do find it occasionally handy when map checking and looking for a certain number listed on a map, only to find out it was calculated from... This however happens seldom enough that I tend to resist specifying CFR's, as "omg, isn't this self evident".

[CBarrett]

kwilson: "But it seems your question is when to use what some of us refer to as CFR or calculated from record."

No, I wanted to know if anybody designates lines as "calculated " when the annotation is obtained from measured data.
Like in the old days, the LS would chain only 3 sides of a rectangle, they would designate those 3 sides "measured" and the 4th side "calculated".

It sounds like nobody does anymore.
I do not either. I agree with dharri: "dimensions determined from measured values represent measured data."

Three sides measured and the 4th calculated in the old days could possibly indicate that it was not a closed traverse, and therefore when retracing it you can expect to see greater error. This could play a role in whether you accept a fund monument or reject it as a possible blunder or informing some other evidence evaluating process.

[Scott]

What do you think of this I got in an email:
"a measured distance can only exist between found monuments. Any distance that is not physically measured is considered calculated. If no monuments exist, then the monuments position is calculated, not measured, even if the position is along a line that has monuments that have measured distances."

I am going to answer:
"Then proposed parcel lines would be designated calculated?
How are monuments set for the proposed parcel lines without measuring?
If no monuments are found on the boundary, then the boundary would be designated calculated?
If the boundary lines are not measured, then how are monuments set for the boundary?
I’ve not heard of anyone doing this."

[CBarrett]

What do you think of this I got in an email:
"a measured distance can only exist between found monuments. Any distance that is not physically measured is considered calculated. If no monuments exist, then the monuments position is calculated, not measured, even if the position is along a line that has monuments that have measured distances."

I am going to answer:
"Then proposed parcel lines would be designated calculated?
How are monuments set for the proposed parcel lines without measuring?
If no monuments are found on the boundary, then the boundary would be designated calculated?
If the boundary lines are not measured, then how are monuments set for the boundary?
I’ve not heard of anyone doing this."

One needs to specify the dataset, or set up a convention at which point a measurement subjected to a calculation, it has been modified substantially enough to no longer represent (whatever is important about the measurements) and why it is important to make that distinction. One may say, well, I measured ...... but this one is just an approximation I got from following calculations and based on following assumptions....

A distance we use for a "measurement" is also a calculation, if one has done their job right. It has either been compass rule or least squares adjusted. Measurements you get from your total station are derived from a series of readings. Even more so if you are repeating angles. If you want to get really pedantic about it even with a single reading, you are measuring time and wavelength, and calculating distances from this data. I forgot how horizontal and vertical angles are read on total stations (optical or some other methods) .

field process we go through, we take readings on our measuring equipment (even if we're talking about a chain, or pacing or a tape) and then we calculate your... 65% or 95% confidence value. We tend to consider this a measured value because the conventional assumption is that it has not been adulterated by things other than measured data, and thus worthy of being called a measurement (as opposed to maybe a blunder). If you want to get extremely pedantic, you can also run down the rabbit hole of how wavelengths are measured and read - more calculations at play.

Define your perspective first and why the distinction is important, then it will not be as difficult to classify what belongs where.

Showing off to one another that we understand the process and can argue the one-up minutia about basics back and forth (leaving the communicator feeling smart and communicatee enraged) is nowhere nearly as important as coming to a consensus what certain technical term means within the profession.

[David Kendall]

What do you think of this I got in an email:
"a measured distance can only exist between found monuments. Any distance that is not physically measured is considered calculated. If no monuments exist, then the monuments position is calculated, not measured, even if the position is along a line that has monuments that have measured distances."

I agree with all of the above statements. I wouldn't necessarily label those boundary lines as calculated but the corner positions are calculated positions until I establish them with monuments. This is why I generally don't consider a no-monument record of survey on a parcel to be valid establishment of the parcel boundary. On the ground establishment is really all that matters. The only exception is when the boundary is referenced to other fixed works, fences, buildings, trees, witness monuments, etc

Then proposed parcel lines would be designated calculated? I believe so but I might not label the lines as calculated
How are monuments set for the proposed parcel lines without measuring? Monuments are set by measuring from other monuments
If no monuments are found on the boundary, then the boundary would be designated calculated? I believe so but I might not label the lines as calculated
If the boundary lines are not measured, then how are monuments set for the boundary? Monuments are set by measuring from other monuments

If I don't have something on the ground representing the position then it is a calculated position

[sharp7823]

dharri: “It is my belief that dimensions determined from measured values represent measured data.”

CBarrett: “It's either calculated from record maps, or measured and derived from your field measured data.”

Agree with both of these comments. It may just be a case of semantics. The EIT’s “calculated” term seems to be the same as the “measured” terms of others (including me). Obviously “calculated from record” needs to be differentiated from calculated from field measurements” in the EIT’s instance.
It may be time to communicate with the signing LS instead.

[khuerth]

It may be time to communicate with the signing LS instead.

...and we now have the correct answer.

I only use "CALC" on my dimensions when I am doing prelim maps or tentative maps and show "CALC" where new distances are being shown based on the proposed line (incremental distance on either side of the new line's intersection with record).

[David Kendall]

The EIT’s “calculated” term seems to be the same as the “measured” terms of others (including me). Obviously “calculated from record” needs to be differentiated from calculated from field measurements” in the EIT’s instance.

Who said anything about EIT?

[Scott]

David Kendall: "Who said anything about EIT?"
Sean has inside info.

The LS is cc'ed on all, but hasn't jumped in.

If anybody has access to a few recent FMs and/or PMs that clearly show:

"a measured distance can only exist between found monuments. Any distance that is not physically measured is considered calculated. If no monuments exist, then the monuments position is calculated, not measured, even if the position is along a line that has monuments that have measured distances."

please send them to me. PM me for my email address.

[CBarrett]

Only time I say 'calculated' on anything, is because a mapchecker has dug their heels in and I don't want to argue.

Numbers I show are my 'final value' which has been arrived to by a process, which should be known to every surveyor. For lay people looking at the map, stating a distance (that I have 95% confidence in) is sufficient.

To make up my mind to voluntarily start differentiating between measured and calculated, someone has to do a very good job convincing me that this is relevant. I am not saying it is impossible, but I am yet to see it.

I should have probably prefaced this statement with a fact that we don't do record data maps (for subdivisions). They are always based on field work and analyzed boundary. I understand that there are parts of the state where record data maps are still acceptable, so maybe 'calculated from' plays a bigger part. I have not had to prepare one, so I don't have very deep insight as to the challenges and minutia.

[CBarrett]

David Kendall: "Who said anything about EIT?"
Sean has inside info.

The LS is cc'ed on all, but hasn't jumped in.

If anybody has access to a few recent FMs and/or PMs that clearly show:

"a measured distance can only exist between found monuments. Any distance that is not physically measured is considered calculated. If no monuments exist, then the monuments position is calculated, not measured, even if the position is along a line that has monuments that have measured distances."

please send them to me. PM me for my email address.

What are you trying to accomplish?
Is this a mapcheck comment? Argument between friends?

[Scott]

CBarrett: "Is this a map check comment?"
Not yet, but it might become one.

I am checking a PM on which the distances on the map are all designated "calculated" unless two found monuments are at the ends of the line being dimensioned.
It is very confusing to me and I have not seen this practice before, but that doesn't mean it is not an accepted practice.

I have not made my mind up yet as to what, if anything, I am going to comment about the practice on the map.
I wanted to get input from others on the forum as to common practice before deciding what to do.
I have also inquired to multiple local County and City Surveyors for their advice.

I informally emailed the question "How is it determined whether a distance is designated measured or calculated on this map?" to the tech and cc'ed the LS. I received the answer posted here and I have not yet replied.

If anybody has access to a few recent FMs and/or PMs that clearly show the practice please send to me.

[CBarrett]

When I check maps I usually have "suggested comments" which are optional to make. Those are comments that may clarify drafting, or suggest more conventional (for the area) way of presenting things. Then I have 'required' comments, which is something you can insist on because it is codified in subdivision map act or in PLS act. "Suggested comments" are mostly a teaching tool for me, for surveyors who are noticeably new to map preparation, or to the area customs.

So in your case, not having seen the map - so you may need to modify what I say) Suggestion: more conventional way to notate ..... whatever they are notating) and then show them an example of how it is done locally. if they disagree, I don't believe you can make them change it, unless the superfluous data makes something really misleading and technically incorrect. Difficult interpretation which takes more time is not necessarily technically incorrect. Interpretation likely to lead someone to a wrong conclusion can be argued to be technically incorrect.

With my own technicians, if they do something unusual, my recommendation is, don't waste the mapchecker time and good will (and I tend to make them change it, or hopefully teach before a lot of changes need to be made). Cost of an in-house technician is a lot lower than that of a city/county mapchecker. On a flip side, it is often much easier for a consulting engineer or surveyor to justify extra $4000 in map checking fees, rather than extra $4000 mapping budget (assuming a large tract map).

Make sure you understand your role as a mapchecker - what is it that your city or county surveyor is certifying to on the map?