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 Excluding Vertical Angles from Least Squares Adjustment

kyle kenna's profile image
kyle kenna posted 03-22-2023 17:31

Prior to doing a least squares adjustment I have noticed it is possible to split radiations so both the horizontal and vertical components can be disabled individually. Unfortunately, when completing the adjustment both the horizontal and vertical components of the radiation are still used in the adjustment unless the whole radiation is disabled. Is it possible to disable the vertical component of a radiation when doing a least squares adjustment so only the horizontal component is used in determining the position of the point? The least squares adjustment averages all radiations to determine the height of the point. This becomes a problem when long radiations are averaged with short or close radiations to determine the height of the point.

ian bissonnette's profile image
ian bissonnette

not sure if you are running the traverse adjustment or the network adjust. i don t know the background computations that tbc does, and also do not use the traverse adjust. but if you run the network adjust then i do know there is a setting in the setting cog that asks: “perform vertical adjustment”. if you unclick this then vertical is left alone. not sure if you can manipulate the observations how you want afterwards. 

if you make all your control points “control” quality then you can also assign different amounts of movement to them in the network adjust. maybe there is a way here to trick tbc into holding the vertical of certain points if you know the vertical is good on them. or letting them move less.

hope this helps. 

kyle kenna's profile image
kyle kenna

Hi Ian,

Thanks for getting back to me. I am using the network adjust and am aware of the horizontal adjustment only. As the name suggests it does not adjust or compute any heights for any of the points. When I am looking at the properties of the total station observations there are options for how you would like to use the radiation. The default option is set to horizontal and vertical however, there are options for horizontal and vertical only as well. If a radiation is flagged as being out for vertical position or fails the standardised residual test in the adjustment report for its vertical residual it would be great to make the radiation a horizontal only observation so the observation can still be used in determining the horizontal position of the point. However, I have found after making the observation a horizontal only measurement the vertical angle is still used in the adjustment and the network adjustment report will still flag the same observation. The only way to fix this is to disable the entire observation. Generally, I still have enough redundancy in the network to get away with removing the observation. However, it would be good to take the vertical component out of some of the longer lines to get a more accurate height for the point.

Andrew Haukås's profile image
Andrew Haukås

I'd like to know if this is possible as well. Being able to separate the components and disable or weigh them individually would go a very long way toward making TBC my single solution for network control.

kyle kenna's profile image
kyle kenna

Hi Andrew,

Yes this is probably the one thing I can see missing from the adjustment which would make it ideal. At the moment particularly when doing long radiations you need to disable the whole radiation if the height component is out of the tolerance. Often the horizontal reading is fine but because you can't separate the two components you end up excluding the whole radiation from the adjustment and as a consequence reduce your redundancy.