Activity Feed › Discussion Forums › Strictly Surveying › Books on projections, coord systems
Books on projections, coord systems
Posted by nate-the-surveyor on June 8, 2021 at 12:35 amIs there a book out there on projections, coord systems, related stuff, types of coord systems etc?
I’ve tied into some work performed by one of the big engineering firms locally. Basis of bearings is stated to be State Plane Grid North. Nope. It’s geodetic, without saying where their base was. Or what theta to apply.
And, another job more recently. Theta has been applied twice. So, the bearings are not on geodetic, but are twice theta from geodetic, and once theta from grid.
Now, I know I don’t know it all. But, I’m seeing a genuine need for a book that is in plain language, simple enough for me to understand,, and complex enough to accomplish the task of a normal modern surveyor.
Thank you,
Nate
stlsurveyor replied 2 years, 10 months ago 16 Members · 26 Replies- 26 Replies
This free download should help with some of that.
http://www.ejsurveying.com/uploads/2/5/6/6/25668328/working_with_grid_coord.pdf
.I haven’t found one, Nate. What I find is that they look promising until we get to the question that I want answered. Then they either stop or enter into their own world which is often irrelevant and sometimes plain wrong.
For example, this otherwise excellent old guide to Virginia DOT surveys gets very close in sections 10.08 through 10.10. but then it just quits and veers off into monkeyed-up state plane coordinates.
An indication to the real source of problems like the ones created by your engineer friends may be found in this GIS exchange. Just compare the myriad paths described and recommended and compare those to GPS points collected and then black-boxed into state plane coordinates in survey software. There may really be two issues: 1) understanding coordinate systems and 2) understanding software.
You’ve mastered these relationships well. Whatever you did to identify the problem is a key learning objective for those who haven’t and should be part of the workflow.
How did you do that?
USGS Professional Paper 1395
GPS for Land Surveyors , by Jan van Sickle
Yep, this is the one. Might seem intimidating at first, but give it a minute. Very straightforward and, as it says, a true “working manual”.
- Posted by: @mathteacher
Whatever you did to identify the problem is a key learning objective for those who haven’t and should be part of the workflow.
How did you do that?
The blunt answer makes me look smart, but that’s not real fair. There was a fair amount of “reasonable guesswork” applied.
I took the nomenclature “true north”, and saw the lines drawn on a globe, that converge at the poles of the earth.
And, I saw the term “Grid” in grid north, and saw non-converging lines.
Overlaying these 2, I saw theta, or convergence.
Then, I struggled mentally with these 2 superimposed images, and realized we are shifting the “backsite”, not the “foresite”.
Thus, a grid bearing will have a higher azimuth number, if I’m west of the central meridian, (which is where “true” or geodetic bearings are the same). Than a true bearing.
Laplace correction was not significant, for my purpose, as my instrument was not that caliber.
So, I’ve been using grid bearings, with solar observations, for well over 35 years.
My sun shot software allowed me to compute sunshot, with both grid brgs and geodetic brgs.
But, even before I had that, I used to compute sunshots, with scaled lat longs from a USGS. quad sheet. I’d artificially do the shots twice, once where I’d taken it, and once at a place 1 mile east, or west, to approximate convergence. This way, I could run an open traverse, and close the angles against the sunshots. This gave me specific convergence, for that area, or lat/lon.
My little brother was taking the ICS (International Correspondence Course) at the time. We used to talk alot. He taught me those big words, like theta, and how to break down section 5, 6 and 7, (when I could not remember what dad had taught me.) Also, Single Proportionate Measure, and Double Proportionate Measure. (SPM, & DPM).
So, when I first got RTK GPS, I bought a used Topcon Legacy E for 25k. I brought it home from Blue Eye Missouri. I took it to another surveyor, (TDS data collector), and asked how to get it to generate GROUND SCALE and GRID BRGS. It could not do this directly. It was a 2 step process. Set it all up, ground scale, and geodetic at the base. Then, go look up convergence, then go reset the prev system, with theta applied.
This I suspect is where most surveyors missed the issue. So, this other surveyor immediately replied “Is this why when I move my base, and back shoot, to my previous base, that there is a little rotational problem?” Well, we went over it, until we both learned. I learned how to do this in the data collector, and he learned the same, and why algebraicly subtracting the geodetic brgs, gave convergence difference.
Well, before this, I’d been using LOCUS GPS. These were 8 channel, L1 only units, that had algorithms to use the lowest sats in the sky.
So, I had tons of jobs, on grid brgs, ground scale. This was why I needed my legacy e system to address this.
Anyway, I’m no genius. I’m intensely practical, and useful, to equip others, (sometimes) by skipping alot of sidetracks.
IF I can once visualize and learn, I can often help others, by skipping alot of peripheral stuff.
Anyway, I’m now a Javad user, as their approach is a real neat screen, that allows all kinds of controll over the way this issue is handled. Not to mention it’s ability to flush out genuine data, in rough places for GPS.
So, that’s my story, of how I got this way.
Time to wake the kids.
Nate
That’s how I learn except that I go from the algebraic to the graphical and back again until what I calculate and what I see match. Sometimes I’m figuring wrong and sometimes I’m seeing wrong, but I keep at it until they come together. It’s a labor intensive, time-consuming process.
The essence of understanding lies in how you know that your work is right or wrong, and that’s what’s missing from so many books. If the book began its discussion with this, for example, “When I can calculate the published bearing from one point to another using trig and Northings and Eastings, then the basis of bearings is grid. Here’s why that is true.” And then proceed to explain the coordinate system.
In teaching math, I saw that I often lost students during long explanations of theory followed by the application. They were worn out before we got to the purpose. Many times, reversing the order provided relevance and helped hold students’ interest. It also helped them think about what the theory was providing.
Nowadays, though, we really have to know how to make field observations and graphical presentations match up. That adds another layer to teaching and learning.
The more we simplify, the more complicated things get and the harder it gets to get things right.
Some students, it’s better to present the problem first, then the math.
Academics tend to present the math…/theory first.
If you present the problem first, then it builds a shelf in my brain first. If you present the math first, then I have a scattered pile of disorganised facts.
Some people can do either, or both. I prefer shelves first.
Thanks,
Nate
- Posted by: @nate-the-surveyor
Is there a book out there on projections, coord systems, related stuff, types of coord systems etc?
I’ve tied into some work performed by one of the big engineering firms locally. Basis of bearings is stated to be State Plane Grid North. Nope. It’s geodetic, without saying where their base was. Or what theta to apply.
And, another job more recently. Theta has been applied twice. So, the bearings are not on geodetic, but are twice theta from geodetic, and once theta from grid.
Now, I know I don’t know it all. But, I’m seeing a genuine need for a book that is in plain language, simple enough for me to understand,, and complex enough to accomplish the task of a normal modern surveyor.
Thank you,
Nate
I agree with Mr. Mayer. Van Sickle has been great reference throughout my career.
Also check out “Datums” section in Caltrans Survey Manual found in the link below.
Hope this is helpful.
http://dot.ca.gov/programs/right of way/surveys-manual-and-interim-guidelines
-Justin
If you are looking for a Handbook type publication, this is quicker and easier to reference than any of my textbooks on projections, SPC or convergence.
@gene-kooper Yup…got that one too. I have used PP-1395 so much that it’s held together with Duck Tape (or duct tape, whatever).
If you can get your hands on one of the old NAD27 books for your state, those are full of information explaining how to. Working through “hand” calculations from field observations to geodetic conversions.
Nothing beats doing it with pen and paper.
I find it amazing how many excursions into 1980’s era government publications people are wiling to do to avoid spending $73.02.
@mathteacher Oh, god. Sometimes I really hate WGS84 AND web Mercator.
In the latest ISO 19111 (spatial referencing by coordinates AKA coordinate reference system data model), the concept of a ‘datum ensemble’ was introduced. The idea is that 4326 (2D WGS 84) and its relatives is really a generic and degraded version of a particular geodetic datum. If you state that your data is WGS 84, it really could be any of the WGS 84 realizations–there’s no way to know–so you’ve just lost valuable metadata and downgraded the data. We’re working on how we want to implement the concept.
So yeah, there’s a ton of data out there supposedly on the “WGS 84” datum which is really on just about any ‘modern’ readjustment/realization out there.
“NAD83” has been in practical use as a datum ensemble too, at least in the GIS field. Yes, we’re (GIS folk) all demon-spawn and stupid and don’t understand the difference between accuracy and precision. Okay, maybe there are a few people who know better. We’re trying and we’re willing to listen.
I also curse the day that someone decided using Mercator on a sphere with a radius of 6378137 for web maps and then say it was [based] on WGS 84. My company had to overlay data on these web maps and we ended up publishing and enabling a whole lot of people to publish web maps on web Mercator. I’m (and my team, and others) are trying to make it easier to publish web-based data using the correct coordinate reference systems and not the blankety-blank web Mercator system.
So back to that Esri forum thread. We (Esri) only have a few transformations that go between modern CRS and WGS 84 because there aren’t many. It’s usually possible for a geodetic agency to model a transformation between ITRFxx and the local CRS which then may get copied as also usable for “WGS 84” with or without a particular realization by assuming equivalencies between a certain ITRFxx frame and WGS 84 realization. When questions come up like the forum question, it ends up a scavenger hunt to figure out where the “WGS 84” web map data came from as that will dictate what transformation(s) to use for other data. Australia’s really running into this now because there are “WGS 84” web maps now which are really on GDA94 and others that are on GDA2020…which are offset by over a meter.
Disclosure: I work for Esri and have been on the ISO 19111 maintenance committee/working group and am on the the subcommittee that maintains the IOGP / EPSG geodetic registry.
I’m just one of those evil GIS people. Bwah-hah-hah! Seriously, I do coordinate systems and transformations at Esri.Most traditional map projections books focus on the algorithms only. So hopefully you get spherical and ellipsoidal equations (if they exist) plus convergence and Tissot / distortion equations. There’s little to no discussion of datums/geodetic/geographic coordinate reference systems. This includes John P. Snyder’s books, Richardus and Adler, Syffus and Grafarend (that’s a tough book), Qihe Yang, Canters, Pearson, etc.
Jan van Sickle does incorporate both and so does Iliffe and Lott is the latter is more slanted towards GIS, not land surveying.
Beyond van Sickle’s book (and I can’t check to confirm that he talks about it because it’s a work, and we’re still WFH), I can’t think of any that discuss combined scale factors or dealing with a local coordinate system that isn’t tied to a geodetic CRS. I didn’t learn any of that in my fancy grad program at Ohio State. They may have dealt with it in the undergrad surveying program.
I’m just one of those evil GIS people. Bwah-hah-hah! Seriously, I do coordinate systems and transformations at Esri.I suspect that some of the same things affect surveying conversions from WGS84 to NAD83. From some of the Trimble Business Center localizations that I’ve seen, what’s going on in the black box is not clear at all. Using HTDP to match TBC coordinate changes leads to frustration. And, I think, the version of WGS84 that finds its way to the GNSS receiver is determined by the adjustment source, CORS or some other service. I think it likely that the source of the problem in the GIS thread is related to that, given that they seem to be using a new receiver.
I laughed out loud at your demon spawn and stupid comment. When I left the world of corporate mathematics and entered the world of mathematics education, most of my new colleagues would have applied those terms to me. Fact is, though, it’s really just slightly different personalities that initially select corporate over school, but people routinely move between those two worlds. Both solve similar problems using similar tools, but the focus is different and what’s usable in one is garbage in the other.
Perhaps the surveying and GIS worlds have similar characteristics. Meanwhile, web Mercator really isn’t so bad. It’s wrong for almost any lat/lon you might enter, but it gets close to almost all sources.
@nate-the-surveyor asked for a book, not for himself necessarily, but for folks who may be creating problems. Here’s a quick read from Trimble that covers a wide area. It’s in three parts and written for GIS projects, but there’s a good bit of information relevant to others, including what really determines the coordinate system in the GNSS receiver:
Coordinate Systems in Trimble GIS Workflows | Trimble Geospatial
@mkennedy posted an informative reply above. Upon rereading it, I felt that I might have used poor judgement in posting the link to the GIS discussion. My purpose was not to belittle or insult the participants. Instead, it was to emphasize both the complexity and ubiquitous nature of coordinate systems. If I breached an etiquette rule or was otherwise improper, I apologize.
My limited work with QGIS showed me immediately that coordinates in GIS systems could be a major problem. If the same collected data were submitted to a GIS and used for a published survey, would only the GIS be subject to coordinate transformation errors?
@mathteacher No worries! I’m well-aware of the shortcomings related to coordinate reference systems and transformations in the Esri software. I’m trying but it takes a while! The GIS people reference was a joke on me.
I’m just one of those evil GIS people. Bwah-hah-hah! Seriously, I do coordinate systems and transformations at Esri.Understanding Software is exactly it. And I swear every manufacture has a different jargon and a different expected workflow.
-All thoughts my own, except my typos and when I am wrong.
Log in to reply.