Inquiry: Direction of Z-axis in JAG3D Software

Dear JAG3D Technical Support,

I hope this message finds you well. I am currently a user of the JAG3D software and I have a question regarding the orientation of the Z-axis in the software.

While analyzing the calculations performed by JAG3D, I noticed that the displacement in the Z-axis is calculated using the following formula: Z0 - Z, instead of Z - Z0. This has intrigued me as I would like to understand in which direction the Z-axis is oriented in the software.

Could you please clarify whether, in JAG3D, the Z-axis is directed upwards or downwards? This information will be crucial for me to correctly interpret the results and calculated displacements in the software.

Thank you in advance for your attention and valuable assistance. I look forward to receiving your response to continue my work with a clear understanding of the axis orientation in JAG3D.

Best regards,

Hi,

in geodesy, the x, y, and z-axis points in the north, east, and up direction, respectively. JAG3D uses the geodetic convention.

All the best
Micha

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

Dear Micha,

Thank you for your previous response and explanations regarding the axis orientation in JAG3D. I have encountered a real-life situation in monitoring a house where I am facing some confusion.

In this case, the target "C" has initial coordinates of (X0 = 5535.046459, Y0 = 8090.582053, Z0 = 21.937977). After performing some work, the new coordinates become (X = 5535.046459, Y = 8090.582053, Z = 21.937977). When I calculate the displacements by subtracting the initial values from the current values (delta X = X - X0, delta Y = Y - Y0, delta Z = Z - Z0), I obtain the following results: (delta X = 0.012655, delta Y = -0.008216, delta Z = 0.005266).

However, the values displayed in the delta (x, y, and z) columns in JAG3D seem to be reversed. According to JAG3D, the delta values indicate that the house is moving upwards. However, the reality on the ground suggests that the house is actually moving downwards, consistent with the values displayed in JAG3D's delta columns.

To assist you in better understanding the situation, I have prepared screenshots that show the calculated results as well as the values displayed in JAG3D. You can view them at the following links:

Screenshot 1: [https://ibb.co/0JhRTVs]
Screenshot 2: [https://ibb.co/CB6FjYX]

These screenshots clearly illustrate the discrepancy between the calculated results based on the actual coordinates and the values displayed in JAG3D.

Thank you for your attention and assistance. I look forward to your response.

Best regards,

Hello,

first of all, you are using a outdated version of JAG3D. I recommend to check the latest version.

Concerning your question, in geodesy, we use two terms to describe a deviation, i.e., error and correction. Both terms have the same magnitude but different signs. A correction is added and an error is subtracted, i.e.,

$l=l_0+corr$ vs. $l=l_0-err$.

Regards
Micha

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

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