RPLS#, post: 418304, member: 12280 wrote: At the company I've worked at in the past SOP to establish vertical control has been to check into two vertical NGS benchmarks with RTK and then set site benchmarks that will be used for on-site vertical control. 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?
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Hey, Sean Oro/FrancisH, just to shake your memory the original question was with respect to a design topo project, not bathymetry!
Your alter ego, FrancisH was all over the "map" with his vituperative. His posts went from "discussing" topo surveys, RTK surveys, static GPS, post-processing, and bathymetry. I stand by my comment regarding his archaic method of mistreating geoidal separations. Frankly, there is no reason for him to post about bathymetry in a thread about a design topo project, so you can wait all you want.
From your FIG paper reference, page 14, "Geodetic Vertical Datum"
When the height of an object is expressed it must be related to something. The height of a ceiling is relative to the floor. The height of a building is relative to the ground outside. The elevation of a mountain is relative to Mean Sea Level (MSL). The expression MSL, when applied to elevation, usually refers to the height above the local geodetic datum. The Canadian Geodetic Vertical Datum (CGVD28) and the USA North American Vertical Datum (NAVD88) are referenced to MSL at Rimouski, Quebec. These systems are realized through the physical monuments in the ground, and they move with the continental plates. The elevations of all reference marks (bench marks) within the two systems are related to MSL at Rimouski through precise leveling and gravity observations. These geodetic vertical reference datums do not coincide with observed MSL at any other location due to local atmospheric and oceanographic effects.
The vertical reference datums used by U.S. surveyors are the NGVD29 Datum and NAVD88. If we are using GPS gear and want elevations (e.g. NAVD88), we use a geoid model. The current NGS model is GEOID12B.
Now I see that you got banned as FrancisH and have decided to use an old sock puppet to fling some more poo before being banned once again. Til then I'll put you on IGNORE, Sean Ora from England.
Sean Ora, post: 420976, member: 12254 wrote: Waiting.
Waiting.
Waiting.
Waiting.
[MEDIA=youtube]m7mIy97_rlo[/MEDIA]
[INDENT][INDENT]
Warren Smith, post: 420979, member: 9900 wrote: Sean,
You seem to be in a different time zone, and it doesn't appear to be Greenwich.
So what are you now saying? I am no longer a British Surveyor if I am not in England at the moment?
Still waiting for our links.[/INDENT][/INDENT]
Ignorance may be bliss, but it does make for some odd page views:
These geodetic vertical reference datums do not coincide with observed MSL at any other location due to local atmospheric and oceanographic effects.
What are you talking about? The topic of the FIG paper is the valid use of direct conversion from ellipsoid to chart datum using a constant factor.
FIG is a SURVEYING association, it is not a bathymetry ONLY survey body but covers all aspects of surveying.
You were saying the direct constant shift from ellipsoid to MSL is on OLD method when the paper itself is from 2014.
Jim Frame, post: 420989, member: 10 wrote: Ignorance may be bliss, but it does make for some odd page views:
Jim Frame
Where are your links? Proof? You had the time to make all those screen grabs and yet all I was asking is a link to disprove the ellipsoid->MSL method.
Clearly this guy is clueless, he called me the creme dela creme of the US Surveying community. :smarty:
So I guess the amrican surveyors have these in common:
1. Practice surveying based on their archaic ways
2. When someone from an international community points out their way of doing things and it does not conform with their practice
they ridicule that person without first checking if his method is accepted internationally.
3. When asked to back up their claim they throw insults instead of providing a technical basis for their claims.
4. Getting links from youtube seems to be their practice of providing proofs to their claim
Edward Reading, post: 420993, member: 132 wrote: Clearly this guy is clueless, he called me the creme dela creme of the US Surveying community. :smarty:
In our country, we throw away the creme that floats on top of the milk batter.
I'd look into height modernization, google is neat like that, you will find a ton on how us US Surveyors going to be getting lazier by advancing with the times, kind of like graders do with those GPS doohickey's on their scrapers. 11 pages of posts, not 1 surveyor advocated cutting a corner, check, check and double check, regardless of method is what I read. I think its funny FrancisH, that a few months back you were predominantly advocating calculating a boundary from minimal distant horizontal control, but now you seem to understand extending geometry from a distance introduces distortion.
BK9196, post: 420996, member: 12217 wrote: I think its funny FrancisH, that a few months back you were predominantly advocating calculating a boundary from minimal distant horizontal control, but now you seem to understand extending geometry from a distance introduces distortion.
I guess you have not really read into the difference of GPS results between horizontal & vertical distances. Horizontal results are more accurate than vertical values - almost 2x.
If you have the time, open up the spec sheets of your equipment. Look for the word - "accuracy" on the spec sheets then move your eyes a little bit to the right of that word.
Sean Ora, post: 420994, member: 12254 wrote: So I guess the amrican surveyors have these in common:
1. Practice surveying based on their archaic ways
Provide a reference
2. When someone from an international community points out their way of doing things and it does not conform with their practice
they ridicule that person without first checking if his method is accepted internationally.
There are plenty of international Surveyors that frequent this board, and provide constructive insight and share idea's, typically its good conversation and we all learn from eachother.
3. When asked to back up their claim they throw insults instead of providing a technical basis for their claims.
Provide a reference for your claim.
4. Getting links from youtube seems to be their practice of providing proofs to their claim
Sean Ora, post: 420998, member: 12254 wrote: I guess you have not really read into the difference of GPS results between horizontal & vertical distances. Horizontal results are more accurate than vertical values - almost 2x.
If you have the time, open up the spec sheets of your equipment. Look for the word - "accuracy" on the spec sheets then move your eyes a little bit to the right of that word.
Done it, its key to know your equipment and its limitations, nice conversation, you're not worth the time.
Maybe I missed it but where in that paper does it advocate not using a geoid where possible?
mvanhank222, post: 421003, member: 8673 wrote: Maybe I missed it but where in that paper does it advocate not using a geoid where possible?
Really? Your proof of something is because there is no proof? Hope your lawyer if you need one in the future won't use that line of defense. Really?
I need to sit down and digest what you just said.
Provide a reference
Strange you all of a sudden require references when this was what I was asking all day long and no one even dared to answer with a link.
I've read a little more in the referenced FIG paper. It seems they are defining chart datums that allow the user to go directly from GNSS measurements and tide info to the ocean depth at a location. The user does not need or use orthometric elevations or geoids because all the necessary information, including the variation induced by gravity, is in the chart.
Rather than saying geoids are irrelevant, on page 20 it talks about using a geoid model to interpolate between measured points for the separations of the chart.
There is also this relevant statement on p. 20.
"A simple SEP shift can be determined ... This single value can be used in the local area only, where the assumption that the spatial variation in chart datum, geoid, and TSS [topography of sea surface] is at a minimum."
This means that the method proposed by FrancisH, whereby he considered ellipsoidal height and orthometric elevation to be equally usable without geoid corrections, is limited in its applicability, perhaps to regions such as a harbor or small bay.
That's pretty much what several of us were telling him - that it was an approximation that would work for some applications, but not all, and one should understand its limitations.
This means that the method proposed by FrancisH, whereby he considered ellipsoidal height and orthometric elevation to be equally usable without geoid corrections, is limited in its applicability, perhaps to regions such as a harbor or small bay.That's pretty much what several of us were telling him - that it was an approximation that would work for some applications, but not all, and one should understand its limitations.
So his method was correct right? He did mention that this was how bathymetry survey was done as lined out by the IHO yet you ridiculed his method saying he lacks understanding of geodesy.He mentioned bathymetry survey so I would assume that you know that these are done near bodies of water right?Not swimming pools. So his method based on what you said is valid for his location. From what you said, it seems that most of you also lack understanding in geodesy. You don't seem to know when a certain method is valid or not.
Same troll, different name.
Nothing to see here folks. Move along now.
So you wait for us to provide a link while ridiculing us for using Google? That's actually funny.
BTW, we are the link dolt.