FrancisH, post: 420533, member: 10211 wrote: Please answer for me another question....
If you think your geoid model is so accurate then why the need to do actual topography survey?
why not just get your x,y,z from the geoid model itself????hahahahahhah
...because the geoid is a model of a geopotential surface, not a topographical surface.
I think FrancisH might be TDD.
For anyone interested in knowing about the Singapore Height Datum (SHD) here is a PDF of a 2015 FIG presentation by Dr. Victor Khoo of the Singapore Land Authority.
https://www.fig.net/resources/proceedings/2015/2015_07_vrfp_comm5/5A_Khoo_Singapore_Height_Datum.pdf
After the introductory material, the description of the SHD and the tide gauge at Victoria Dock begins on slide 20. Descriptions of the precise leveling networks begins on slide 24. The Singapore Satellite Positioning Reference Network (SiReNT) is discussed starting with slide 43.
AND, most importantly for anyone other than FrancisH, a discussion of the Singapore Geoid of 2009 (SGeoid09) begins on slide 48. Slide 54 has a nice graphic of the SGeoid09 "geoid model" or Converter (N). It shows a nearly 2 meter increase in geoidal separations from west to east. The Singapore Land Authority also provides a web page calculator.
It is a free service provided by SLA to users for converting ellipsoidal heights obtained in the SVY21 coordinate system (discussed earlier in the presentation) to a height value reference to Survey Department's datum.
Cliff Mugnier wrote an article on the Singapore horizontal datums in his "Grids and Datums" column in the January 2006 issue of the Photogrammetric Engineering & Remote Sensing journal.
http://www.asprs.org/a/resources/grids/01-2006-singapore.pdf
And I will now follow Mr. Frame's sage advise....where is that Ignore button?
Edit: Well, that sure cleaned up this thread!
Kevin Samuel, post: 420741, member: 96 wrote: I think FrancisH might be TDD.
I've been mulling over his alter ego as well. His tactics seem eerily familiar.
base9geodesy, post: 420418, member: 7189 wrote: Since the U.S. National Geospatial-Intelligence Agency (NGA), who are responsible for the definition and maintenance of World Geodetic System 1984 (WGS 84) do not provide any form of high accuracy terrestrial realization (e.g. passive or active control) how to you get WGS 84 values with any level of integrity in Indonesia? If it is by an autonomous solution then the probable uncertainty in position, both horizontal and ellipsoid height could easily be in the range of 2-5 meters. I would ask our poster from Indonesia if he has ever attempted to process his observations with respect to one of the several on-line positioning services such as the Australian AUSPOS on the U.S. OPUS. Both services would reach out to use CORS in the IGS network and there appears to be at least 3-4 in the area of Indonesia. They would both return ITRF values which NGA considers equivalent to the current realization of WGS 84 (G1762).
Well I generally believe my iPhone.
hahahaahahh to the EXPERT SURVEYORS OF THE USA,,,,
From FIG (International Federation of Surveyors) or maybe US surveyors are not member of this international organization hence the lack of experience in GNSS...
When using GNSS heights to remove the vertical vessel movement, traditional water level gauges are no longer necessary for the reduction of observed depths. Instead, separation models are used to transform the depths from the ellipsoid to chart datum.Shore based water level gauges are also used to establish chart datum at GNSS water level buoy or bottom mounted gauge located at the survey site. Establishing chart datum at offshore locations helps to anchor separation models.
In short transfers of elevations are done directly from ellipsoid heights (not geoid model) to chart datum (MSL/MLLW).
The separation model here is the diffirence between readings from the GNSS ellipsoid height and MSL/MLLW elevation at the water level gauges. MSL/MLLW height are derived from tidal observations.
Hahahahahhahahaha
So US surveyors have NO IDEA how to use GNSS to transfer vertical heights to MSL/MLLW datum???
hahahahahahahahah oh boy, a bunch of mrons practising surveying in the US and people wonder why their boundary survey system is in such a mess????
hahahahhahahahaha
Warren Smith, post: 420748, member: 9900 wrote: I've been mulling over his alter ego as well. His tactics seem eerily familiar.
Lol - I thought TDD stood for Too Damn Dumb.
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If anyone wants to study the full FIG paper, you can find it at
https://www.fig.net/resources/publications/figpub/pub62/Figpub62.pdf
Also similar at
http://www.theses.xlibx.info/t1-other1/909493-3-ellipsoidally-referenced-surveying-for-hydrography-international-fe.php
I haven't studied this paper in depth to understand the goals of their hydrographic surveys, but I note that it does discuss geoid models.
Kevin Samuel, post: 420741, member: 96 wrote: I think FrancisH might be TDD.
TDD rarely posted about the technical aspects of Surveying. When he did he was knowledgeable.
What's amazing is RPLS#'s question has generated 10 pages so far, I wonder if he got what he needed:cool:
RPLS#, post: 418304, member: 12280 wrote: Supposing I don't have an RTK setup, are static gps observations an acceptable way of establishing vertical control for a design topo project? Any guidelines or recommendations?
I haven't read all 10 pages so i suppose it's already been said; but I think it's worth repeating:
The datum for every project you do is project specific. weather you're doing a topo for a septic design or developing quad maps of the United States; it's all about the meta data. If you give the client enough information to relate his data, or any other data, to the data you provided for the project, you've done your job
MightyMoe, post: 420801, member: 700 wrote: What's amazing is RPLS#'s question has generated 10 pages so far, I wonder if he got what he needed:cool:
Did that answer his question? LOL:innocent::smarty:
RPLS#, post: 418304, member: 12280 wrote: Supposing I don't have an RTK setup, are static gps observations an acceptable way of establishing vertical control for a design topo project?
Transferring elevations by levelling is usually preferred but using GPS is legitimate in certain situations. Static is going to be somewhat better than RTK. So if RTK meets your needs, certainly static would.
As far as my input into the original discussion....I would say it all depends on the particular job. An "assumed" elevation might be okay and if some specs call for first-order work, then so be it. If you are using a basic elevation from an existing NGS mark, I would agree that you should check in to at least one other mark to have some kind of confidence in the stability of the mark you used. If you are claiming first-order work, I believe you need to check in to three relative bench marks at the beginning of your run, and three at the end after you establish a mark on your site (which might include running through much more than 6 marks until you can find six that have relative precision. That in itself might prove very time-consuming from my past experience.
The biggest concern I would have is that your statement as to what exactly you used and your basis of elevations is very clear. It's funny how a request for a quick-and-dirty topo job can suddenly be being used as real and true elevations for floodplain or some other concern to it being "true" elevations.
(No further comment as to use of GPS and RTK for establishing local bench marks, except that I would suggest checking into more than one established mark and stating very clearly what your basis of elevations is.)
On a side note, I have been entertained by FrancisH's contributions in the past, but it can sure hurt an otherwise good thread with people trying to argue with the adjoining inanity.
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I haven't studied this paper in depth to understand the goals of their hydrographic surveys, but I note that it does discuss geoid models.
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and yet you commented as if you had knowledge of what he was saying? So you were just blabbing and inflating your ego on a field that you have no experience or right to comment upon?
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I haven't studied this paper in depth to understand the goals of their hydrographic surveys, but I note that it does discuss geoid models.
[/QUOTE
and yet you commented as if you had knowledge of what he was saying? So you were just blabbing and inflating your ego on a field that you have no experience or right to comment upon?
I haven't studied this paper in depth to understand the goals of their hydrographic surveys, but I note that it does discuss geoid models.
and yet you commented as if you had knowledge of what he was saying? So you were just blabbing and inflating your ego on a field that you have no experience or right to comment upon?
On a side note, I have been entertained by FrancisH's contributions in the past, but it can sure hurt an otherwise good thread with people trying to argue with the adjoining inanity.
especially when surveyors who have nill knowledge of what was being discussed chime in as if they had a life long experience on the topic.
now that he had given source of his claim from an international surveyor's association, I would like to hear all those that said his method was wrong to either admit their incompetence or show proof of their claim that his method was wrong? any print from an organization with published methodology would be sufficient to back up your claim that his method was wrong.
either that or shut up.
TDD rarely posted about the technical aspects of Surveying. When he did he was knowledgeable.
but he did give a source for his claim right? how about you, where is your source for claiming his method was wrong?
show proof or shut up.
Hmm - we seem to be gathering an international cadre of nay sayers vis a vis American surveyors ...
I've used the Ignore button twice now, though I'm not sure it wasn't on one person with two accounts.