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MichaelGrupp / evo

Python package for the evaluation of odometry and SLAM
https://michaelgrupp.github.io/evo/
GNU General Public License v3.0
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different time scale for the same dataset #558

Closed Masoumehrahimi closed 1 year ago

Masoumehrahimi commented 1 year ago

hi I want to know why the time scale is different in the following two plots? they are gained from the same dataset. one of them is from 0 to 200s, while the other one is from 0 to 600s?

ape-global-rtabmap ape-global

MichaelGrupp commented 1 year ago

One is absolute (see the exponent) and the other is relative to the start of your data. If you want to use relative in evo_traj, add the --plot_relative_time option.

Masoumehrahimi commented 1 year ago

thanks for your response but what does it mean absolute and relative for mentioning the time?
(what does the value of 450 mean in the time scale?) would you please explain a bit more?

thanks

MichaelGrupp commented 1 year ago

Absolute means using the original value of the timestamp in the plot, relative means displaying the elapsed time relative to the first timestamp in your data.

Your trajectory has absolute timestamps that are large numbers, probably because they are UNIX epoch timestamps like 1687436912.491856. The long value is just displayed more compact in the plot by subtracting an offset, you can see this from the offset +1.643888e9 in the lower right corner.

Masoumehrahimi commented 1 year ago

Thanks a lot