I'm locating some section corners and I do have a plat of three of them to compare. The statement on the plat for bearings and distances says; "the bearings & distances shown are relative to true north and are ground distances".
I'm regretfully doing an LDP (TM) on this job and I figure my bearings will match within a minute or so. I'm using a surface projection with the LDP so the distances should also be very close. That doesn't happen, so I convert to the local state coordinate system and hit his with a few seconds and a couple of hundredths.
It was early in the GPS era and he maybe wasn't exactly sure how to handle the transformations.
I'm guessing the bearings were cousins or maybe a nephew of true north.
Still trying to puzzle out what relative the distances would be.
I can't count how many times I have encountered stuff like that.
It will never end!
Loyal
I just worked on a little problem where the plat says oriented to true north. Appears to me that north in this case is Utah Central SPC's grid north. I just found and rotated to the two basis of bearing corners and it worked out, sure not astronomic or geodetic north. Plat from 2000, not sure very many GPS'ers at that time had much clue as to what they where looking at on the display screen. The easy option was to go with an SPC out of the black box. Must be true north, eh? Black Magic!
Loyal, post: 449765, member: 228 wrote: I can't count how many times I have encountered stuff like that.
It will never end!
Loyal
Nah, it won't.
I think he may have just got the units, and probably was a bit unsure how to make them work or use them.
Anyway, I wish I could pull a few I have out there from the 90's:confused:
Grid north, is true north, at the central meridian... So that does make 'm cousins!
Ground distance and grid distances, are... Only 1 csf apart. So, maybe they are neighbors!
I just made that mistake a couple of months ago. I copy and paste notes, legend, north arrow, description, ect. from drawing to drawing and I just forgot to edit the bearing statement. I don't do much in state plane but I had done 60,000 feet of topo last year and part of the project was to show right-of-way along the topo corridor. I Imported the monuments located on this project to start and overlooked the fact that I had previously used grid bearings. Also matching coordinate systems involves a few key strokes and not much thought.
If I only had a dollar for every error I found on a plat or for every error I saw while plotting the mylar.
Signed
Not so perfect
billvhill, post: 449832, member: 8398 wrote: If I only had a dollar for every error I found on a plat or for every error I saw while plotting the mylar.
Amen.
Well... state plane bearings are "relative" to true North.
billvhill, post: 449832, member: 8398 wrote: If I only had a dollar for every error I found on a plat or for every error I saw while plotting the mylar.
Me looking at screen 5 seconds after sending plot
I think it is a sad reflection on our profession that some do not know the difference between so called "true" north and grid north, or between grid and ground, etc yet they are producing plats and surveys. I could understand a new CAD person not knowing, but I see this from licensed individuals as well.
I remember a county surveyor in CO (licensed of course) that called me after we set a bunch of monuments in his county. He went out and shot between some of the intervisible pairs, and was getting 0.7 feet difference on a 3000 foot sight, and larger differences on longer ones. I asked if he applied a scale factor to the EDM distance. Silence. Crickets chirping.
Of course engineers are no better. I have tried explaining several times to engineers why surface stationing is different than stationing derived from SPC, or the whole idea of grid to ground, but it doesn't seem to register. This is the reason I say every civil engineer should have to take a basic surveying course to understand issues like that, not to make surveyors out of them, but to be able to understand survey data.
John Hamilton, post: 449908, member: 640 wrote: I think it is a sad reflection on our profession that some do not know the difference between so called "true" north and grid north, or between grid and ground, etc yet they are producing plats and surveys. I could understand a new CAD person not knowing, but I see this from licensed individuals as well.
I remember a county surveyor in CO (licensed of course) that called me after we set a bunch of monuments in his county. He went out and shot between some of the intervisible pairs, and was getting 0.7 feet difference on a 3000 foot sight, and larger differences on longer ones. I asked if he applied a scale factor to the EDM distance. Silence. Crickets chirping.
Of course engineers are no better. I have tried explaining several times to engineers why surface stationing is different than stationing derived from SPC, or the whole idea of grid to ground, but it doesn't seem to register. This is the reason I say every civil engineer should have to take a basic surveying course to understand issues like that, not to make surveyors out of them, but to be able to understand survey data.
You turned in a plat with state plane distances?
aliquot, post: 450134, member: 2486 wrote: You turned in a plat with state plane distances?
I sure have, the last one was for a mining corporation that has an engineering company doing design.
That company seems to be run by the GIS department when it comes to title and legal issues.
After a few conversations and some back and forth with data I finally saw the light and decided everything I do for them with be in the state coordinate system. Still didn't take care of all the issues but it sure makes things run smoother, however, there are a few boundary plats I did that needed a lot of explaining on the plat so no one will be confused.
State plane plats were big in the late mid to late 70's driven by mines and the DOT. Often the mines would do them as simple state plane while DOT would expand to a surface using a DAF.
IMHO a boundary survey in SPC is a crime.
I just finished a topo survey for design of a new grade-separated bike path. The client requested that the topo be on SPC, which is reasonable given the modest combined factor (about 0.99996, as I recall). However, I had to file a Record of Survey for the right-of-way establishment, and I referenced that to some legacy surveys for direction and used ground distances in order to more directly illustrate the differences between measured and record. I explained that in my cover letter to the client, but I expect to get some questions in response.
aliquot, post: 450134, member: 2486 wrote: You turned in a plat with state plane distances?
where did I say that? Not that I think there is anything wrong with that as long as it is clearly stated.
John Hamilton, post: 450178, member: 640 wrote: where did I say that? Not that I think there is anything wrong with that as long as it is clearly stated.
I thought you did because you said the county surveyor neglected to scale his total station distances.
Jim in AZ, post: 450165, member: 249 wrote: IMHO a boundary survey in SPC is a crime.
If it doesn't clearly indicate so then I think we would all agree. If properly noted, I would hope any licensed surveyor could deal with it.
I can certainly see how property owners, architects, and construction engineers would be confused.
aliquot, post: 450193, member: 2486 wrote: I thought you did because you said the county surveyor neglected to scale his total station distances.
I read it as John set monuments for a geodetic control network, aerial mapping control, or control for defamation monitoring that confused the county surveyor, not monuments set for a plat, because (if you've been paying attention) that's what he does for a living 😉
It was a monument network covering a county. Almost never do anything like a plat, although there are rare occasions...
But, since you mentioned it, why would it be so wrong to do so IF it was plainly stated on the plat? Jim in AZ seems to thing so as well. Not arguing with you, just wondering why it would be so wrong (or, as Jim says, a crime)
