# tf timing issue with point cloud filtering

Hi everyone,

I'm trying to filter a point cloud by means of the available passthrough filter nodelet. It works fine so far as long as I filter the untransformed point cloud in the frame it is originally published in.

I'd like though to filter the point cloud in the world frame. For this purpose there's the ~input_frame parameter which, I understand, tells the passthrough filter to first transform all point coordinates into the set frame. The problem is that the transformation through tf complains about that it is unable to be performed because the time stamp needs to be extrapolated into the past. The delta between the correspoding stamps is only about a fraction of a second, say, some hundred milliseconds. Still it does not work.

I'm not sure what's wrong here and would be happy if someone could point me in the right direction.

Thanks!

It might be related to the fact that I create the point cloud by means of stereo reconstruction using elas_ros. Due to the resolution of the camera images (1920x1080) it takes elas_ros some time to generate the point cloud (about 5 - 10 seconds). But I'm not sure.

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