So How Accurate Do They Think It Will Be ?
JB, the word "approximate" in your post, caught my eye. Maybe the GMAP guy can help with this. LOL:-P
Large-Scale Integration is already possible!
In my opinion, this is a very important thread. I read it earlier this morning and spent several hours developing a response posted on the Global COGO web site - http://www.globalcogo.com/possible.pdf
My goal is to bring the "abstract" to "reality." I remain convinced that the surveying profession has an enormous contribution to make. That is not to say that other disciplines have it wrong or don't do it "right."
But, the fact is, there are many benefits to be realized and, in the big picture, the umbrella 3-D concept is not really that difficult or challenging - except that "we don't do it that way." That argument can be overcome by those willing to look into the details and understand the underlying concepts.
Statewide parcel map - Greatest Hits!
:good:
I like what they did in Kitsap County, but don't get to use it much....
do you know much about this?
I've xref'ed in a section map, just to see how it looked, compared t my survey; and it was exactly where I had defined my lines....
My jaw dropped open....:-O
I also found the contours to be right on!
Doug
I don't think you are really going to love this reply!
We have had a torrens system in Ohio since 1913. It has proven to be extremely unpopular for a variety of reasons and has been implemented in only a few counties.
http://www.deeds.com/information/Land-Registration-System-in-Ohio-1343669081.html
Large-Scale Integration is already possible!
Good to see you here Dr. Burkholder! What a great opportunity for the Wisco surveyors! Go get it done.
Once the Tenth Amendment is repealed, the plans can go forward.
Next Generation National Elevation Dataset
> Idividual county systems in Wisconsin range from 1:20,000 to 1:50,000 accuracy.
>
> The statewide system might be 1:2,000. There is significant dropoff in accuracy with elevation differences. How many users are going to include elevation data?
>
> Paul in PA
Interesting timing. I just received the following from the USGS through the Ohio Geographically Referenced Information Program (OGRIP) mail list. OGRIP is Ohio's effort to coordinate GIS development between government agencies, utilities, universities and private industry. I have had various levels of involvement in OGRIP since 1994.
Have only had a few minutes to scan the proposal. However, this appears to be an effort to develop a national, LIDAR based, digital elevation model and could answer part of Paul's concern.
>FYI,
>A new report about the proposed next generation of the National Elevation Dataset (NED) is now available online from the U.S. Geological Survey (USGS).
>A Conceptual Prototype for the Next-Generation National Elevation Dataset
>Stoker, J.M., Heidemann, Hans Karl, Evans, G.A., and Greenlee, S.K,
>U.S. Geological Survey Open-File Report 2013–1023, 52 p.
> http://pubs.usgs.gov/of/2013/1023/
> http://pubs.er.usgs.gov/publication/ofr20131023
> http://pubs.usgs.gov/of/2013/1023/ofr13-1023.pdf
> > … The NED, which provides bare earth data originally derived from
> > U.S. Geological Survey (USGS) topographic quadrangles, is in 2012
> > being primarily developed from light detection and ranging (lidar) data
> > and interferometric synthetic aperture radar (IfSAR); however, the
> > NED does not currently exploit the full range of products that can be
> > extracted from these source data. As a result, the USGS NGP is
> > not realizing the full benefits from its investment in or the capabilities
> > of these technologies. Lidar provides a rich set of three-dimensional
> > (3D) points, much of which is not being used when only bare earth
> > information is provided. The purpose of this study was to explore a
> > conceptual system to take full advantage of elevation source data and
> > derivative products and services to meet the Nation’s elevation needs. …
>NED is the elevation component of the National Map.
> Best regards,
> Charley
> _____________________________________________________
> Charles Hickman - Geographer - U.S. Geological Survey
> National Map Liaison to Ohio [and Michigan]
> 6480 Doubletree Avenue Columbus, Ohio 43229 USA
> chickman@usgs.gov (614) 430-7768 http://www.usgs.gov/ngpo
> _____________________________________________________
> Elevation and The National Map http://nationalmap.gov/elevation.html
> 3D Elevation Program (3DEP) http://nationalmap.gov/3DEP/
Now I will need to read through the documents.
Large-Scale Integration is already possible!
Thanks for the response and the links.
Question: how far can the central point of reference be taken for the delta E N U ? Say you have a route survey 20,100, 300 miles? What is the rule for limitation?
Large-Scale Integration is already possible!
Yours is a good question with several answers - I'll try to be correct and concise.
1. There is no distance limitation. Using the 3-D Pythagorean theorem and ECEF X/Y/Zs, one can compute the 3-D spatial distance between points with no distortion using square root (delta X squared + delta Y squared + delta Z squared).
2. But I believe your question is really related to the "flat earth" distance in a tangent plane projection from the point of reference (P.O.B.). For that I refer you to page 32 of the following link - http://www.globalcogo.com/localcor.pdf
3. What is your tolerance and how far do you need to go in layout/local work? Using ECEF X/Y/Z as primary values (they don't change) the user can "move up" to any new P.O.B. and perform "flat earth" computations/work on the local delata east, delta north, delta up values from that user-selected point. See 3-D diagram at http://www.globalcogo.com/BK001.pdf
If you have additional questions, I'll field as best I can.
actually, that is extrememly interesting and similar to the system in NC (which is also unpopular). In fact it is so unpopular that not one surveyor I know is even aware of its existence!
Large-Scale Integration is already possible!
What's the difference between your tangent projection and a Plane projection (from my Trimble Surveyor Controller software).
I usually use a Transverse Mercator for my projects. It's better (in my opinion) than a plane or tangent because I can account for the round earth in one direction. So I can get a long strip where the distortion is not to great. Using a plane or tangent projection the width of the low distortion strip is the same in both directions. Most of my projects are small enough that the tangent would work but the Mercator also works just fine.
I use GPS and so all my data in the background is stored 3D ECEF. So I think I'm already tapped into the advantages. I keep everything anchored to OPUS derived control points so I believe I'm 5 cm or better (if you trust OPUS).
Where things would go complicated is when trying to reverse calc the data from a 2D projection of any type into ECEF. Without the elevation you can't do it. So you are left to estimate the elevation if you don't have an accurate elevation. Estimated data will yield estimated results.
Large-Scale Integration is already possible!
Mr./Ms. LRDay;
If you feel my answer is too flipant, you might be right. I don't mean it that way.
1. I can't answer your first question because I don't know specifically what algorithm Trimble has programmed into their data collector. But, rest assured, the programmers at Trimble are smart and they know everything (all the details) included in the GSDM.
2. I will neither criticize or brag on what Trimble does (or the other vendors). But you need to consider the business model they use. I am not critical of our capitalistic system, but vendors don't stay in business unless they offer products and services their customers will buy. My observation is that the vendors do an excellent job with their market research and are successful accordingly.
3. You make an excellent point. You can get 2-D as a sub-set of 3-D but it just doesn't work going the other way - unless one estimates the third dimension (notice I did not say 'elevation'). That gives me an opportunity to high-light the stochastic model component of the GSDM.
4. The GSDM includes the provision for the user to input a standard deviation with any/all measurements. In doing that, the standard deviation of each derived answer is readily available and the user can see specifically how the "estimate" affects the answers. Note - a reasonable approximation for the third dimension has little impact on the qualtiy of horiztonal - see "Accuracy of Elevation Reduction Factor" published in the August 2004 issue of the ASCE Journal of Surveying Engineering. I'd post a link to it, but ASCE frowns on my posting links to articles I've written for which they hold the copyright. But, go to the Global COGO web site and get my email address. Send me a request and I can (according to ASCE policy) send you a draft copy of articles I've written.
Large-Scale Integration is already possible!
I didn't think anything was flipant. I'm a Mr. (Leon).
I'm not trying to promote Trimble it's just what I'm familiar with. I realize how the basic math works using ECEF and 3D coordinate geometry. Most maps are presented as a 2D model that we can lay flat on a table. So hence map projections (trivial for you I'm sure). But my point is that's how it gets presented and almost all boundary maps/plats/surveys are done this way. An exception is the PLSS which are still flat maps but the record bearings are astronomic. Everybody realizes that a GLO plat isn't going to close using the math.
When I first started using GPS it became clear to me that if you use geodetic bearings and fairly precise measurements around a parcel and especially with great elevation change that even though the measurements where precise that they wouldn't close in the standard sense as used in boundary mapping. It wouldn't bother me so much but your work would get rejected by many public agencies if you turned in a plat like that (it wouldn't close). But maybe that's the whole point to have easy math. They are still trying to flatten out a round world. So projections solve that problem. I'm not saying that there may not be a better way but it's probably a steep climb to get over it.
Some folks want the whole state or large portions of state to be reported in a state plane projection. They want all the bearings on the boundaries to match up across vast expanses. It doesn't bother me and what you advocate doesn't bother me either because the continuity of the 3D coordinates would be just fine. The differences on bearings for the same line on adjoining surveys would just freak out a lot of folks. I'm sure you've heard this before as you indicate it probably won't be implemented for a long time. I don't like SPC's because neither the bearing or the ground distance matches the ground measurement but it sure does make a nice big flat map.
I'm already keeping all my survey data in a 3D manner and have it tied to the world coordinate system. I can load any of my DC files into a project file I'm working on in any of the projections I use and the data shows up in the right place (converted at input). I don't know how it works in other software but if the software can't do this it's not worth much.
If your system was available to use with the commercial equipment and software available I'd probably use it. I've basically been doing what you advocate for several years now by creating my own local project projections. It works great and is simple to do once you understand it.
Large-Scale Integration is already possible!
1. There is no distance limitation. That's wonderful but surveyors are required to produce a flat earth product. The mark to mark products are not in demand.
2. But I believe your question is really related to the "flat earth" distance in a tangent plane projection from the point of reference (P.O.B.). So distortion of some magnitude is a requirement to deliver the demanded product.
3. Using ECEF X/Y/Z as primary values (they don't change) the user can "move up" to any new P.O.B. and perform "flat earth" computations/work on the local delata east, delta north, delta up values from that user-selected point. It seems to me the moving up would cause a mismatch in a route survey flat earth map.
I think I might agree that ECEF system could be the best solution for a statewide database. But the statewide map needs to be some sort of distorted projection. The smaller the area of interest, the less distorted the map product.
Large-Scale Integration is already possible!
The shapefiles or polygons that make up the parcel layer should be coded with either the lat/long/height or ECEF coordinates. That way the GIS could project them in any flavor (projection) the user wished. So yes Large-Scale Integration is already possible and probably already integrated.
Statewide parcel map - Greatest Hits!
Another good one, (not in the thread)
Large-Scale Integration is already possible!
I'm trying to wrap my mind around the POB concept. Wouldn't a seperate map be required for each move up POB in a route survey? Therein lies the rub for me if that's the case.
Large-Scale Integration is already possible!
I apologize for the delay in responding.
By computing the local tangent plane differences (delata easting and delta northing), those differences with respect to the P.O.B. are identical to working with latitudes/departures - plane surveying.
For an example, see http://www.globalcogo.com/3DGPS.pdf
Other examples are also available.
