Extract Depth From Depth Image

  • I have a pmd tof sensor and I am able to see its imagery using voxl-portal or rosrun image_view but how can I extract the depth of the points in mm? Is there an easy way to do that while I do some testing or do I have to write something up to subscribe and print the various points out?

    Is there a handy logging tool of somesort that could give me an array of depth points?


  • Dev Team


    We have a feature in the works for our voxl-logger project that would allow it to log tof data to a file. In the meantime, you can use voxl-inspect-points to look at a subsample of the points, or copy and modify the source to process the data however you'd like.

  • Thanks @Alex-Gardner ,

    If I enter voxl-inspect-points tof_pc -n then is the z axis supposed to be depth in mm? Is there a scale that is supposed to be applied to get between float and distance?

    Also is something like the following the expected output? It just says Float XYZ.
    timestamp(ms)| # points | # bytes | Format
    8104565 | 38528 | 462336 | Float XYZ
    8104628 | 38528 | 462336 | Float XYZ
    8104696 | 38528 | 462336 | Float XYZ
    8104758 | 38528 | 462336 | Float XYZ

    I can start going through the source, I just want to make sure I understand everything so I can get the correct depth in distance extracted.

    Thanks for your help.

  • Dev Team

    Hey @amiranda,

    For the tof points, each axis is measured in meters, no scaling is needed.

  • Okay, in the meantime, I ended up creating a subscriber for the tof_pc and I managed to extract the x,y and z points. Im assuming that the z point that I extracted from the voxl_mpa_to_ros is the same as the one used in voxl-inspect-points, so that z axis is also reported in meters correct?

    Thanks for you help so far.

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