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).
Oh boy, I've gotta make some popcorn and watch this.
If
FrancisH, post: 420360, member: 10211 wrote: hahahahahahhahaha
I use static results to orient my survey azimuth to plane after transformation. I observe 2 intervisiblestations (~100m apart).
Most of the time I compare the distance - hor & vert -with GPS results. Most of the time it gets ~1-2 cm (hor) but to say you are off by 2-4 mm is
ridiculous. The circular mark in your optical sight in your triback already covers ~2mm? Your nail on the forsight has a diameter of ~2mm?
That in itself covers your 2-4 mm intrinsic error.[/QUOTE
If a person loses 4mm centering a tribrach, both the surveyor and tribrach need replaced.
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).
What he is doing (I think) is to use the elevation on a given bench mark for his ellipsoid height, he has no shift between ellipsoid or elevation, as the survey progresses the ellipsoid height and the elevation are the same number. This is how many surveyors worked back in the early days to do tasks such as oil well staking.
MightyMoe, post: 420421, member: 700 wrote: What he is doing (I think) is to use the elevation on a given bench mark for his ellipsoid height, he has no shift between ellipsoid or elevation, as the survey progresses the ellipsoid height and the elevation are the same number. This is how many surveyors worked back in the early days to do tasks such as oil well staking.
Yes, I think that you are right. I remember people doing this in the 90's when RTK first came out. It can really make a mess of things.
Edward Reading, post: 420422, member: 132 wrote: Yes, I think that you are right. I remember people doing this in the 90's when RTK first came out. It can really make a mess of things.
Lots of GPS users did that, probably still do;)
MightyMoe, post: 420421, member: 700 wrote: What he is doing (I think) is to use the elevation on a given bench mark for his ellipsoid height, he has no shift between ellipsoid or elevation, as the survey progresses the ellipsoid height and the elevation are the same number. This is how many surveyors worked back in the early days to do tasks such as oil well staking.
Moe,
Back in the early 90's when I started out using GPS commercially the geoid models were almost non-existent. The software I used at the time, TrimNet, would allow us to best fit the rough geoid model to existing BM's tied in our campaign resulting in a residual geoid model that was then used to develop the orthometric heights we required. Of course this was before the advent of RTK so everything was static and we did not have to worry about getting the ortho values in real time. I don't think GNSS software has allowed this operation since the days of TGO or maybe even TrimMap. Out here in the west just forcing the ellipsoid to fit a single base will not work very far. The drastic changes in geology create bumpy geoid model around here as well as western WY I would suppose.
John Putnam, post: 420427, member: 1188 wrote: Moe,
Back in the early 90's when I started out using GPS commercially the geoid models were almost non-existent. The software I used at the time, TrimNet, would allow us to best fit the rough geoid model to existing BM's tied in our campaign resulting in a residual geoid model that was then used to develop the orthometric heights we required. Of course this was before the advent of RTK so everything was static and we did not have to worry about getting the ortho values in real time. I don't think GNSS software has allowed this operation since the days of TGO or maybe even TrimMap. Out here in the west just forcing the ellipsoid to fit a single base will not work very far. The drastic changes in geology create bumpy geoid model around here as well as western WY I would suppose.
I remember doing something very similar, there was a way to calibrate and include a geoid model, it never worked very well:(
FrancisH, post: 420392, member: 10211 wrote:
Jeeez, all these surveyors in here and not one even understood ellipsoidal concept in gps receivers.
This thread just keeps on giving!
Let me fix that sentence for you.
"Jeeez, all these surveyors in here and only poor FrancisH doesn't understood ellipsoidal concept in gps receivers"
Please keep going, it's hilarious reading.
Mods: Can we create a comedy section of the forum for these threads? Someone might read his posts later and be gullible enough to believe some of them.
Sent from my SM-G935F using Tapatalk
Someone knows as much about Geodesy as they do about US boundary surveying. 😉
Not sure what happened on my post. The statement was:
If a person loses 4mm centering the antenna its time to replace both the surveyor and the tribrach.
Loyal, post: 420377, member: 228 wrote: Well...I don't know who said it first, but he was right:
"YOU CAN'T FIX STUPID."Loyal
Ron White...
hahahahah so let me get this, you guys are saying you have to use a geoid model to get accurate vertical values????
hahahahah so pls answer this, how do you update the geoid model if you are using your receivers to model the construction
of a vertical highrise? every few weeks the receivers will be placed on the next floor level.....
Or you have not heard of receivers being used to monitor verticality of high rises????
hahahahahaahhhahahahahahahaha
the geoid model only reflects a point on the ground as your takeoff point. after that initial value, your rover's position is determined RELATIVE to your BASE!
hahahahhahahaha
I don't think geoid model means what you think it means.
See previous post hahahahahahahah
NGS updates the Geoid daily, you just have to know to install the updates! They model high rises all the time.
In the alternate FrancisH reality, geoid and hemeroid are interchangeable terms. Both are predictable just as water flows down hill, so does this thread.
Hahahaha ..... yawn.
FrancisH, post: 420505, member: 10211 wrote: you guys are saying you have to use a geoid model to get accurate vertical values???
... model the construction of a vertical highrise?
All verticals are relative to something. If you only want verticals relative to a base in one geographic location, then it doesn't matter if those are relative to the ellipsoid (as the GNSS reports most directly) or orthometric relative to a geoid.
If you are carrying vertical numbers from one geographic location to another, and care for the precise values that reflect the flow of water, then you need to recognize that gravity is not precisely uniform over large areas, and therefore the flow of water will not follow what the GNSS tells you without also taking into consideration that gravity difference. The usual way to do that is with a geoid model. The diagram shown earlier in this thread indicates how that is done.
For very large scale hydrology, dynamic heights are theoretically better than orthometric heights, and both take into account gravity differences. The distinction is usually insignificant and ortho is easier for moderate size construction projects. Read about the Great Lakes Datum for an example of where dynamic heights are used.
All this is explained in elementary surveying books. A text on geodesy would be too difficult to follow as an introduction.
I don't think geoid model means what you think it means.
so I guess that means you don't know what it means......hahahahahahahah
NGS updates the Geoid daily, you just have to know to install the updates! They model high rises all the time.
did you answer my question.
are you saying that the elevation used by GNSS to monitor high rise construction that goes up on weekly or even daily basis means that the geoid model at at point of the high rise is being updated daily too?
YES or NO???
hahahahahahaahahha
please read up on the basics of GNSS surveying. hahahahahhaha very funny thread...brings out the dimwits who think that the orthoheight from their ROVERS is based on a geoid model. hahahahhahahahah
