# 1D parameters and datum points

Hi

How I can type leveling standard? I need to put value of 1mm/km of 2mm/km if you see picture there is oa, ob(sqr(d)) and oc(d) so in which area I need to put 1 or 2, or I need to put something else?

also I want to ask for datum points. what is difference between reference and datum point?
if I want datum on all points I need to upload file only in datum points?

if I want for example datum on one point, I need to upload file with one point in datum points and file with rest of points in new points?

if is it correct for wat I can use reference points?

Thanks and best regards!

## 1D parameters and datum points

Hello Tasa,

How I can type leveling standard? I need to put value of 1mm/km of 2mm/km
if you see picture there is oa, ob(sqr(d)) and oc(d) so in which area I need to put 1 or 2, or I need to put something else?

The distance depended uncertainties for leveling networks are denoted by σb. You should set σb = 1 mm (or σb = 2 mm) and σc = 0. Since JAG3D does not support σa = 0, you have to select a small number that does not effect the stochastic model, e.g., σa = 0.001 mm

if I want datum on all points I need to upload file only in datum points?

Yes, that is correct.

if I want for example datum on one point, I need to upload file with one point in datum points and file with rest of points in new points?

Yes, that is correct, too.

if is it correct for wat I can use reference points?

You can use reference points, if you have, for instance, some kind of official coordinates that should be fixed.

Kind regards
Micha

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

## 1D parameters and datum points

Thanks for answer Micha, I appreciate it.

Now I want to ask same questions but for 2D.
If I want to put 2 + 2ppm for distance then I need to put in distance: in oa = 2 (mm)
, oc = 2 (ppm) and ob(sqr(d))=0? is it correct?

What I need to put for angle(direction), if I have instrument standard of 1'' - 0.31mgon, what to put in oa = (mgon), oc = (mm) and ob(sqr(d))= (mm)?

Also for example if I have 4(x, y) points can I put datum on point 1 (both X and Y) and on point 2 but to put datum only on Y? Is this possible?

Thanks,
Best regards.

## 1D parameters and datum points

Hello,

the equations defining the stochastic model are given in the Wiki. Even if the content is in German, the equations are interpretable.

Now I want to ask same questions but for 2D.
If I want to put 2 + 2ppm for distance then I need to put in distance: in oa = 2 (mm)
, oc = 2 (ppm) and ob(sqr(d))=0? is it correct?

Yes, this is correct.

What I need to put for angle(direction), if I have instrument standard of 1'' - 0.31mgon, what to put in oa = (mgon), oc = (mm) and ob(sqr(d))= (mm)?

You have to set σa = 0,3 mgon. If you don't have any further uncertainty, the σb and σc are zeros. Usually, a centring uncertainty has to taken into account. Let say, you are able to point the centre of the target with 1 mm, in this case, you can specify this further uncertainty by σc = 1 mm.

Also for example if I have 4(x, y) points can I put datum on point 1 (both X and Y) and on point 2 but to put datum only on Y? Is this possible?

Yes, but this is a academic construction not used in any practical application. The stochastic points can be diverted from its intended use to reach such a configuration. For instance, you have the points A, B, C and D and xA, yA and yB should be used for defining the datum, xB, C and D are parameters to be estimated. C and D are new points but A and B are stochastic points. Create a file like

A <yA> <xA>  0.00001  0.00001
B <yB> <xB>  0.00001  100.0

The three components that define the datum are fixed (due to the large weight) and xB is a (more or less) free parameter.

kind regards
Micha

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