David
Kris,
I like that! We'll have to see if Kent approves.
Dave
Kent's work attire
Since shucking State Plane our Metadata is very simple
> Is there a standard of practice in Texas when it comes to doing boundary work using RTK or is this the 'wild west' you're talking about.
There are standards of practice governing the reported results, but not specifying methods and procedures.
Since shucking State Plane our Metadata is very simple
> > Bearings related to a local grid having an origin of N Lat: Y and W Long: X
> > Distances are expressed in US Survey Feet as measured horizontally along the surface of the Earth.
> > Geographic Coordinates are referenced to NAD83, 2011 Adjustment, Epoch 2010.
>
> This fixes the relationship between the grid origin and NAD83, but what fixes direction?
:good:
Since shucking State Plane our Metadata is very simple
I did give that some thought, Jim. It's a good question. Ultimately I came to the conclusion that the basis of any geodetic projection will be Geodetic North or some rotation from Geodetic North. Absent any mention of a rotation value (such as may be found in a stereographic or oblique Mercator projection) it seemed understood that the basis would be geodetic. This, by the way, is the same assumption we make of State Plane Systems. I've not seen anyone express that State Plane bearings are coincident with Geodetic North along the central meridian. It's understood to be the case.
Having said that, I count you and Glenn as knowledgeable surveyors. If my metadata is sufficiently vague to cause two competent surveyors to be unclear about my meaning, I should perhaps revisit my approach. What wording would make it more clear for you?
Since shucking State Plane our Metadata is very simple
> Yes, what a freaking nightmare: each tract with its own projection.
Those are your assumptions, not my words, Kent. City-wide and even county-wide projections offer low distance distortions while still affording a convergence that is close enough to North to at least avoid being cartoonish.
> What a giant leap backwards.
By all means, keep surveying in the 1930's. I'm sure I can still retrace your work.
Since shucking State Plane our Metadata is very simple
> I've not seen anyone express that State Plane bearings are coincident with Geodetic North along the central meridian. It's understood to be the case.
Actually, it's explicitly stated in the metadata when you use the Texas Coordinate System. The obvious difference between the Texas Coordinate System of 1983 and a Home Brew projection is that the metadata for the former is found in the Natural Resources Code. There is no need to recite it in full detail as the Home Brew projection requires.
Since shucking State Plane our Metadata is very simple
I like a lot of hops in my home brews.
Since shucking State Plane our Metadata is very simple
> Actually, it's explicitly stated in the metadata when you use the Texas Coordinate System. The obvious difference between the Texas Coordinate System of 1983 and a Home Brew projection is that the metadata for the former is found in the Natural Resources Code. There is no need to recite it in full detail as the Home Brew projection requires.
Actually it is NOT
Texas Natural Resources Code Establishing the Texas Coordinate System (1927 and 1983)
Please show me where the definition of "North" is given at the origin of any of the Zones listed in the Texas Coordinate System.
Since shucking State Plane our Metadata is very simple
the problem i've found, over and over again, in a practical sense: "your survey doesn't fit in our GIS".
project projections scaled about a "midpoint" seem to bypass this nightmare altogether, at least in every instance where i've encountered it.
it sucks, yes, and i wish my terms weren't being dictated to me by people whose business is dealing with cartoons, but should i wish to continue generating income, i have to work within the reasonable confines of what is acceptable to those who ultimately decide whether that check is written.
as stated above, i yield to your knowledge, consideration, effort, and conscientiousness. i also wish i was doing your work. the implied subtext of many of your comments, however, is that the rest of us are falling short either ethically or procedurally- which may be true in a theoretical vacuum, but is certainly not the case in terms of dealing with the work that feeds us.
Since shucking State Plane our Metadata is very simple
> > Yes, what a freaking nightmare: each tract with its own projection.
>
> Those are your assumptions, not my words, Kent. City-wide and even county-wide projections offer low distance distortions while still affording a convergence that is close enough to North to at least avoid being cartoonish.
>
>
>
> > What a giant leap backwards.
>
> By all means, keep surveying in the 1930's. I'm sure I can still retrace your work.
I also assumed "local grid" meant per tract/job/at most subdivision. A city-wide or county-wide coordinate system to me isn't local any more. Part of that is because it's meant to be used by more than one person.
Melita
The ugly parts of RTK that I am finding is in line with the same thing that was absent in a survey the same people made with TS or Robot.
The crews show up and if they can not find the correct or enough monuments and evidence from one setup, the eyeball the rest instead of going beyond the immediate range of their setup to locate what else is needed.
The RTK guy shows up with the short range antenna and cannot reach out far enough to get position of that R/W monument or other boundary markers that are too far away.
Then there is the 3ft error to the monument that is under the Red Cedar.
The few times I've contracted an RTK guy, they never shared their original files and they made sure everything matched near perfect by calculating a scale factor against my TS control.
At least they shared the opus report for the control points.
Since shucking State Plane our Metadata is very simple
> Please show me where the definition of "North" is given at the origin of any of the Zones listed in the Texas Coordinate System.
LOL. I'd never carefully read that Aggie-looking mess of the definitions of the various zones of the Texas Coordinate System. Basically, they just kept the language from the Act of 1943 that created what is now the Texas Coordinate System of 1927, with no mention of a Central Meridian and describing points with values other than 0,0 as the "origin " of coordinates. That shows once again the value of standard projections: that the projection is well understood even after whoever drafted the law mangled the metadata. :>
The strange thing is that there were model laws developed giving examples of how to describe a Lambert Conformal Projection in a statute.
David
> BEARINGS are based on the Texas Coordinate System of 1983, Texas North-Central Zone per GPS observations. All coordinates are U.S. Survey Feet, NAD83 (CORS96) Epoch 2002.0 per static GPS observations and an OPUS solution through the NGS website. To get geodetic bearings, rotate the bearings shown hereon, clockwise, 00°25'39". All distances are grid and to get surface distances, divide the distances shown hereon by 0.9999XXXX.
The improved version:
Bearings of Lines refer to Grid North of the Texas Coordinate System of 1983 (Central Zone) as computed from GPS vectors,
Coordinates are in units of US Survey Feet and refer to the Texas Coordinate System of 1983 (Central Zone); NAD83 (2011) Epoch 2010.0 as derived from connections to the National CORS network via six one-hour sessions of L1/L2 GPS observations logged on two different days and processed using the National Geodetic Survey’s OPUS-RS utility.
Distances are Horizontal Surface Distances in units of US Survey Feet, computed using a project average Combined Scale Factor of 0.999909
Surface Distance = Grid Distance / 0.999909.
Kent, Don't Be Offended, But...
"Bearings of Lines"
"of Lines" is unnecessary. It's sufficient to just say "Bearings".
"Bearings of Lines refer to Grid North"
They don't refer to Grid North. They refer to a Grid System, and "based on" is better terminology.
"GPS vectors"
I like "observations". More layed-back, less stuffy/sniffy.
"...derived from connections to the National CORS network via six one-hour sessions of L1/L2 GPS observations logged on two different days and processed using the National Geodetic Survey’s OPUS-RS utility"
Kent, that's unnecessarily wordy. How can you afford all that ink and paper? If you did a boundary with a total station, would you include information on how many sets of doubled angles were used?
I thought Kris's Metadata was succinct and to the point.
Dave
> The few times I've contracted an RTK guy, they never shared their original files and they made sure everything matched near perfect by calculating a scale factor against my TS control.
They probably didn't "make sure". They likely calibrated or localized to your control. That just means they did that part correctly. The data collector makes the translation, scaling, and rotation on the fly.
If you want the raw data, I know our data collection system allows the observations to be logged. Perhaps you could request that they provide the raw data.
If you prefered grid coordinates, that would be easy to deliver as well.
Kent, Don't Be Offended, But...
> "Bearings of Lines"
>
> "of Lines" is unnecessary. It's sufficient to just say "Bearings".
If you want to leave out "of lines", I won't fault you.
> "Bearings of Lines refer to Grid North"
>
> They don't refer to Grid North. They refer to a Grid System, and "based on" is better terminology.
No, grid bearings expressed as quadrant-bearing angle or as azimuths definitely refer to Grid North. If they refer to any other direction, they aren't grid bearings.
>
> "GPS vectors"
>
> I like "observations". More layed-back, less stuffy/sniffy.
One little problem, though. GPS observations are typically just raw, unprocessed data. The differential solution from observations is conventionally called a "vector" and that is what is needed for an azimuth solution of any sort.
> "...derived from connections to the National CORS network via six one-hour sessions of L1/L2 GPS observations logged on two different days and processed using the National Geodetic Survey’s OPUS-RS utility"
>
> Kent, that's unnecessarily wordy.
Well, the purpose of that part of the metadata is to give some idea of accuracy and reliability. How do you propose to do that if not by mentioning the duration and number of the sessions and the fact that they were on different days?
Kent, Don't Be Offended, But...
Kent,
"No, grid bearings expressed as quadrant-bearing angle or as azimuths definitely refer to Grid North. If they refer to any other direction, they aren't grid bearings."
So a bearing of S43-27-19E wouldn't be a grid bearing then, since it refers to Grid South? I'll stand by what I said, Bearings refer to a Grid System.
GPS "Vectors". OK, point.
"Well, the purpose of that part of the metadata is to give some idea of accuracy and reliability. How do you propose to do that if not by mentioning the duration and number of the sessions and the fact that they were on different days?"
Just add this to the metadata:
"I, Kent McMillan, am accurate and reliable, and I have a clue."
Dave
Kent, Don't Be Offended, But...
>
> "Well, the purpose of that part of the metadata is to give some idea of accuracy and reliability. How do you propose to do that if not by mentioning the duration and number of the sessions and the fact that they were on different days?"
>
> Just add this to the metadata:
> "I, Kent McMillan, am accurate and reliable, and I have a clue."
>
>
> Dave
How about including the accuracy statement from the Data Sheet?
Kent, Don't Be Offended, But...
> So a bearing of S43-27-19E wouldn't be a grid bearing then, since it refers to Grid South? I'll stand by what I said, Bearings refer to a Grid System.
You might have a point if Grid North were not a unique direction at every point in the projection zone of the SPCS. There is absolutely no ambiguity to saying that a particular bearing refers to Grid North of the Texas Coordinate System of 1983 (North Central Zone). Naturally Grid South refers to Grid North as a trivial case.
> "Well, the purpose of that part of the metadata is to give some idea of accuracy and reliability. How do you propose to do that if not by mentioning the duration and number of the sessions and the fact that they were on different days?"
>
> Just add this to the metadata:
> "I, , am accurate and reliable, and I have a clue."
If that were sufficient, there would be no such thing as a bum survey. :>
With static GPS, all other things being equal, the determinants are :
- session duration,
- redundancy, and
- proficiency.
More than one session on more than one day tells me that someone was serious about what they were doing.
