@rover83?ÿ
I planned to work on something for our LDP layer. Unfortunately I was reorganized back to the private sector before I had the chance. Doing it right was beyond a volunteer effort....
I know exactly what you mean. I moved down to WA around the time development of the new zones was really ramping up.
I was happy to donate my own time to the cause. I'd developed some rudimentary tools to automate the LDP development process, similar to the really slick ones that Michael Dennis and his team were using, and I was (still am) pretty excited about the new datums.
Unfortunately, it's really, really hard to get ideas in front of the folks who make decisions at the state level, especially when those ideas promote change, improvement and progress.
I got discouraged pretty fast and dropped it.
The state zones are an improvement over NAD83, to be sure, but I think an extra opportunity was squandered. Especially considering that we have another 2.5 years before the new datums drop. Plenty of time to fix it, but unlikely anything will be done.
Please explain. I don't understand. What needs fixed? Are you saying your state will only have 1 SPCS 2022 zone??ÿ
@bill93?ÿ
It was a consortium of state and county agencies, professional organizations and interested parties that brought it about plus an awesome design team. I was basically a listener and facilitator although I was technically involved in design decisions. As luck would have it our lead designer ended up leading the NGS effort for 2022. The new zones will have the same boundaries as the current but different parameters. Good grief - 8 years ago.?ÿ Link
@norm?ÿ
We will have one statewide zone (top layer), two state-level regional zones (middle layer), but no LDPs (bottom/third layer).
Weighting by population and switching to a single-parallel LCC is definitely going to help. And Washington State is definitely better off than most in that our population centers are close together.
Still, we could have created that third layer and dialed in those numbers even tighter. Not all work takes place in population centers, and being able to move between LDPs which are all around +/- 30ppm rather than SPCS at anywhere from -200 to 200 ppm (this is a low number, I'm just taking into account all the areas we are currently working) would be far preferable.
But maybe I'm in the minority.
switching to a single-parallel LCC
I read that the single parallel LCC are the average of the two parallels, so it doesn't change anything.
I read that the single parallel LCC are the average of the two parallels, so it doesn't change anything.
A single-parallel LCC is the average of two parallels...if you choose to make it the average. The simple average doesn't work out correctly due to changing radius of the earth anyways.
The two-parallel model (at least as used mode widely) assumes scale parity at each parallel. But the single-parallel model lets the user pick the grid scale factor at that parallel.
So the single-parallel model can be tailored to suit depending how far above the ellipsoid the topographic surface lies.
?ÿ
I'm a dummy. I was remembering one of the various iterations our state kicked around in the early stages of evaluation.
The southern half of lower Michigan is basically flat topography, and the final central latitude for the new Michigan South Zone didn't move much from our original Michigan South Zone.
However, based on design criteria offered by the NGS, the central latitude would be at the center (average) of the two parallels at the topographic surface because the zone design dictates the total linear distortion (ppm), which is/should be equidistant from the central parallel. (i.e. no need to list both parallels.)
https://geodesy.noaa.gov/INFO/Policy/files/SPCS2022-Procedures.pdf
d. Linear distortion design criteria. Linear distortion is evaluated at the topographic surface for design, not the ellipsoid surface. NGS designs are based on both coverage area and population distribution (using data from the U.S. Census Bureau). Table 2 at the end of this section gives zone width and height ranges corresponding to various linear distortion ranges. i. The linear distortion design criterion is the smallest specific distortion range of ?ñ5, ?ñ10, ?ñ20, ?ñ30, ?ñ40, ?ñ50, ?ñ75, ?ñ100, ?ñ150, ?ñ200, ?ñ300, or ?ñ400 ppm that satisfies all three of the following minimum percentages: ?? 90% of zone population. ?? 75% of cities and towns (based on location only, irrespective of population). ?? 50% of total zone area.
When it will happen I don??t know but the signs are all around and technology is already in place. ?ÿSooner or later surveyors will have to gain the understanding of the 3d and 4d concepts for all task I believe. Because all others are already moving and moved that direction in architecture, construction, and in advanced engineering task. xYZ has been used in metrology for a while even though it is on a relative site like a manufacturer plant example. ?ÿI had to take the xyz of mechanical engineers designs very great learning curve for my brain and then make that work with a known reference system wgs84. ?ÿThe system of systems. Now the kicker and hardest for me based on equipment was to get them on the flip side to understand was they designed something that fit itself but never truly understood that gravity still had power. Even a 4 foot carpenters level would defy the way it looked in a pure 3 d software. Now once they realized that the site items were going to be built by carpenters and machinist on the surface if the earth that does not have that same set of rules as the ground thaws or dries freezes and anything we attach to it or build on its inconsistent layer of soil grass water is forever changing and we can change it for a moment but she rules and changes as she wants to as well. ?ÿIt was fun mind boggling at times would have to say I learned a totally different set of skills and leaned how to use those skills i knew or I thought knew in ways that were not intended by the two different worlds of something being a plane and 3d and then reality. But good old redneck engineering and goode ole boy adaption and some folks way smarter than i and they were not always those with all academics but the team made up of all aspects of knowledge. ?ÿAcademia builders welders machinist engineers in variety of disciplines all working together to solve and figure out how to build make and measure and quantify all the results. ?ÿ
Sooner or later surveyors will have to gain the understanding of the 3d and 4d concepts
I once heard a licensed surveyor at a 3d training session say, "We're land surveyors, we don't give a _blank_ about elevations."?ÿ Continuing education is a requirement for a reason. Honestly, a person can learn quite a bit hanging around this forum. Some of it's even useful.?ÿ
Sooner or later surveyors will have to gain the understanding of the 3d and 4d concepts
I once heard a licensed surveyor at a 3d training session say, "We're land surveyors, we don't give a _blank_ about elevations."?ÿ Continuing education is a requirement for a reason. Honestly, a person can learn quite a bit hanging around this forum. Some of it's even useful.?ÿ
I had this old-time surveyor tell my partner that he didn't care about those 1/4 corners; "They don't mean anything".
He eventually passed and I was chatting with a young local surveyor from the old-timers area; "You remember old Joe, he didn't believe in 1/4 corners".?ÿ
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Excellent discussion and description of the problem. The attached text, pages 5-9, discusses it well with examples. State of the art in 1915; not sure what the old-timers referenced above studied.
The images above are taken from an NOAA TM NOS NGS - 10 ??Use of Calibration Base Lines? by C. Fronczek.?ÿ
I should have been a flat earth person then also never believed in gravity either and all of this would be simple.
?ÿBut I still have other issues to figure out like as i get older why some things swell and others shrink and its all the wrong parts ????. ?ÿIs any math equation able to fix this.
Love surveying love learning. Great place here for sure to be challenged and challenge others. ?ÿThat is what learning is all about. ?ÿ
