Python hangs at 24398/24400 heatmap images

[memmam]

Confirmed across two runs of the Notebook file. Not sure what's causing it, as no error is produced; Python simply hangs and needs to be forced closed.

[lloydowen8]

This isn't an error but just my shoddy progress bar. When there is a change in canvas tile, i.e. going from 0-{unix_timestamp} to 1-{unix-timestamp} we skip the processing for one step.

This is because we don't want to compute the difference between canvas'.

This behaviour is not monitored in the progress bar.

[lloydowen8]

This should use the tqdm library