Example(s)
Here's a “good example” of modifrickingfied State Plane Coordinates in action:
This is from a formally certified, notarized and recorded Record of Survey filed in the State of Utah (NAD27 version).
“ALL BEARINGS AND COORDINATES SHOWN ARE BASED ON THE UTAH STATE COORDINATE SYSTEM, LAMBERT CONFORMAL PROJECTION, UTAH CENTRAL ZONE.”
“TO CONVERT LISTED COORDINATE VALUES TO SEA LEVEL STATE PLANE COORDINATE VALUES, DIVIDE NORTHING BY 1.0002386; ADD 700,000 TO EASTING AND DIVIDE BY 1.0002386, THEN ADD 1,000,000.00.”
I think this would qualify as a 'recipe.'
Here's a NAD83 version from a nearby Township (same surveyor):
“ALL BEARINGS AND COORDINATES SHOWN ARE BASED ON THE UTAH STATE COORDINATE SYSTEM, LAMBERT CONFORMAL PROJECTION, UTAH CENTRAL ZONE.”
"VALUES WERE CONVERTED FROM NAD83 USING US SURVEY FOOT. TO CONVERT FROM FEET TO METERS DIVIDE BY 3.2808333."
“TO CONVERT LISTED COORDINATE VALUES TO SEA LEVEL STATE PLANE COORDINATE VALUES, ADD 7,000,000 TO NORTHING AND MULTIPLY BY 0.99970848. ADD 1,000,000 TO EASTING AND MULTIPLY BY 0.99970848.”
A simpler recipe (MAYBE), but still a 'recipe.'
Loyal
Interesting discussion but off-base. Unless as Schrock suggests, stirred more vigorously.
1. Map projections (state plane, UTM, LDP) are all two-dimensional models.
2. Surveyors work with 3-D data and should be using a 3-D model.
3. 2-D is a subset of 3-D. Do your work in 3-D (it is easier) and give client 2-D answer (as requested).
4. I recommend two items:
Not really though Tom
I find it rather fortunate that over 90% of my work is in an area that the elevation is between 200ft and 500ft MSL.
The ground and grid is mostly near the same values and I do not have to report my results to any agency demanding different formats than what I work in.
0.02
Tom
Still no Email at this end. I have been having intermittent problems recieving Emails lately, so try it again if you could.
Loyal
> An LDP allows me to work at ground distances, is just as easy to setup in the software (Carlson) as State Plane, is tied to the Geodetic and easily converted to any other system.
>
> While the scale factor in this area is only 0.999913 or .01' in 100', I need to report out ground distances on a survey. I find it a hassle to scale up the grid distances to ground and scale down the record distances to grid. I know the software can handle the scaling but it does not seem to do it for the curves. I find it easier to just to work on ground for a project, and an LDP allows me to do this and still be tied into the Geodetic system.
ok
Tom
Thanks Loyal. I know that sometime emails (at least for me) that go through "Beerleg" get thrown in to the spam inbox.
I was asking for some clarity as to what you don't like. I think I am understanding now. I don't think you need to respond to the email, and I can discuss it here in this thread.
Exactly Dan. exactly.
The need for using either a "modified SPC" or a low distortion projection will exist until engineering software can design in geodetic coordinates. I tend to work on relatively long projects and have been developing my own LDP's since 90's. The engineering calculations for lengths, areas and volumes are much more in tune with the real world and we can stake them out with either conventional or GNSS techniques.
Truncating has no effect on the combined scale factor. As you said, it is a ratio and by definition the scaled vector's length will not change just because the vector is in a different location on the grid. A 1,000' vector scaled up by 1.1 is 1,100.00' no matter what coordinate you start with. You get the same answer if you begin at 0,0 and end at 0,1000 as you do if you begin at 1000000,2000000 and end at 1001000,2000000. The only thing that maters is when you apply the truncation. Leaving the values un-truncated adds to potential problems down the line. I can not count on all of my appendages I have been given coordinates with no documentation that look like a SPC but are not. Leaving us scrambling in the field to find out what was done in the past. The problems with that scenario are much worse than if you are give a coordinate that looks nothing like a SPC but is in-fact a "modified SPC". My personal belief is that anyone that does not truncate a "modified SPC" should be flogged. But that is just me.
A common theme in the "Oil Patch" is for GIS technicians to declare a coordinate system to be a "Modified UTM" and then provide zero metadata on exactly what got "modified."
Thankfully, GIS technicians (most, anyway) have never heard of "combined scale factors." Most of them don't even know about scale factor or convergence angle - a topic never covered in GIS class taught in a Geography Department.
Lord help the Surveyors when they start getting on the bandwagon for LDPs!
I can not count on all of my appendages I have been given coordinates with no documentation that look like a SPC but are not. Leaving us scrambling in the field to find out what was done in the past. The problems with that scenario are much worse than if you are give a coordinate that looks nothing like a SPC but is in-fact a "modified SPC". My personal belief is that anyone that does not truncate a "modified SPC" should be flogged. But that is just me.
Never had a problem with it. You guys must work in a strange enviroment. All the DOT projects come with metadata and you can simply divide the surface coordinates by a factor and get the state plane coordinate (if you want to for some reson, although I can't imagine what that would be), however, if you have given coordinates and control monuments what does it matter if it's state plane or not, if the project has been designed with the values you need to use it anyway. It's not like you should go back and recontrol the project-now I've seen that as a real problem at times.
If I'm given coordinates I never assume what they are. If there's no metadata and no fixed control you aren't going to accomplish much anyway.
I can understand some hesitation I suppose to LDPs but no more than goofing around with modified spc. I can now develop small area LDPs in a couple of minutes before starting a job. Larger city or county sized jobs may require an hour, just to make sure I'm considering the terrain properly.
We expect interoperability between GPS and conventional terrestrial equipment. Our data collectors provide plug and play portability. Our office software can process data from both. The only thing that keeps us from being able to realize the harmony that can be experienced with GPS ands ground measurements is are stubborn dependency on an archaic calculation tool-spc. LDP use makes plug and play a reality.
> Never had a problem with it. You guys must work in a strange enviroment. All the DOT projects come with metadata and you can simply divide the surface coordinates by a factor and get the state plane coordinate (if you want to for some reson, although I can't imagine what that would be), however, if you have given coordinates and control monuments what does it matter if it's state plane or not, if the project has been designed with the values you need to use it anyway. It's not like you should go back and recontrol the project-now I've seen that as a real problem at times.
>
> If I'm given coordinates I never assume what they are. If there's no metadata and no fixed control you aren't going to accomplish much anyway.
If you truncate you can tell at a glance that you aren't on a State-plane. That is an advantage. If you're given "metadata" or not, you should always check raw, measured distances between your existing control ESPECIALLY if you are "given" the coordinates. I've seen crews be given bad data, calibrate to it, do a whole job, and never have a clue that they're not matching actual ground measurements. Being given assumed coordinates, you could still find some points, check measurements between them, and figure out where you are (if things check out).
I can see your point, but I would always feel much safer if I have a coordinate base that doesn't "look" "State Planey". (Oh and I don't advocate not having the metadata. I was just making a point for argument's sake.)
I've seen crews be given bad data, calibrate to it, do a whole job, and never have a clue that they're not matching actual ground measurements.
I think the last time I calibrated a job was maybe tweleve years or so ago. Quit doing it about that time. Had a NAD27 job that the client needed done.
My point is that if you're given a job with "ground coordinates" and "metadata" it is still wise to check ground measurements, and not just plug in the same metadata. It should at least "look" right (the metadata) and the distances on the ground should check. Not checking the control handed to you on a silver platter can be buying the same mistakes the provider of the data published.
Tom Adams (oops, I accidently logged in by my older nickname.)
Oh, I always check the control; I just never calibrate. In fact, checking the control is in almost every contract. The last time I had an issue with control was for two overlapping control networks; and frankly if I had went out there and done a calibration on that job I could have been in a real mess.
I probably would have never seen the issues with the control networks as they were "pretty close" to matching but not quite.
I see a bigger issue with surveyors that want to put "correct" numbers on perfectly fine existing control. Puking out OPUS solutions on long established control points and beating their chest that they "found" some kind of "error". Makes you wonder.
:good:
You Deliver What The Client Wants...
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