# Congruence analysis using JAG3D

Hej Tasa,

I have noticed that in adjustment and deformation analysis for example for 1D height of zero epoch or (Z0 like import data in adjustment) of some point for example is Z0 = 100.00 and after processing is Z = 100.15 (calculated).

Yes, this is possible. Please note, datum points are unknown (new) points, too. These points are estimated within the adjustment process. If the geodetic datum is defined as an average value of several points (instead of some kind of minimal configuration), the datum points get (small) corrections. The size of the correction depends on the quality of the datum definition. In a leveling network, only a single point is needed to define the datum. If so, this (single) datum point will not corrected, i.e., Δz ≡ 0.

In Δz is value of -0.15, Why software sees that point has settlement because there is minus 0.15 but actually point have uplift because new height is 100.15 that mean it is higher for 0.15.

In geodesy (at least in Germany, maybe, you can give me some feedback), we distinguish between an error ε and a correction v. The absolut value is identical, i.e., |ε| ≡ |v|, but the sign is differ: $\hat{l} = l + v = l - \epsilon$.

Points that define the datum are not part of the observation space. Thus, no error can be estimated. However, some users asked me to add some kind of metric that indicates the differences between the a-priori values and the estimated a-posteriori values. Since JAG3D provides the error ε for the observations, the same definition is used for the estimated differences Δ. It seems to be more consistent.

Is that only problem in settings

No, it is just a convention like for the error and the correction. If you need the correction instead of the error, please swap the signs mentally.

Is possible with that software to do pre-processing of network, if is yes do you have some tutorials?

Can you explain, what pre-processing means in your context.

kind regards
Micha

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applied-geodesy.org - OpenSource Least-Squares Adjustment Software for Geodetic Sciences