Importing fixed points with known variances

by bukac, Tuesday, March 26, 2024, 02:52 (32 days ago)

Dear Mitcha,

I have a question regarding the adjustment of a levelling network. Here is the case, I have some fixed heights that are known from another adjustment as well as their corresponding variances. Now I have to include these heights in my adjustment and I don't want them to change, but I want to include their variances as well and not to assume they are error-free.
If I understand correctly the types of points in JAG3d, reference points are fixed points without uncertainties while stochastic points have uncertainties but they get new coordinates during the adjustment.
So, I would like to know is there a way to import fixed points with known variances in JAG3d and adjust the network in a way that these variances affect the results of the adjustment but the imported fixed points remain unchanged?

Thank you in advance!

Best regards,
Blaženka

Importing fixed points with known variances

by Micha ⌂, Bad Vilbel, Tuesday, March 26, 2024, 08:35 (32 days ago) @ bukac

Hello Blaženka,

So, I would like to know is there a way to import fixed points with known variances in JAG3d and adjust the network in a way that these variances affect the results of the adjustment but the imported fixed points remain unchanged?

No, there is no way because this contradict each other. You assume that the points have uncertainties. That means, the positions are only known to a certain extent, i.e., the points are improvable and, thus, not perfectly known (is not fixed).

In some federal states in Germany, a dynamic network adjustment (a network with stochastic points, as you mention) is performed as a final adjustment step to check the reference points for changes (e.g. outliers). If the point changes are insignificant, which means that the deviations are - let say - of random nature, the new adjusted positions are not transferred to the database or to the map (i.e. the new position is discarded).

Kind regards
Micha

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