These are chat archives for PDAL/PDAL

15th
Nov 2017
matt wilkie
@maphew
Nov 15 2017 00:05
Thanks Adam! (actually I'm greedier than my example shows. I've just discovered the number is not Unix epoch or whatever Windows uses but seconds since GPS started, https://geozoneblog.wordpress.com/2013/10/31/when-was-lidar-point-collected/. So pdalinfo --stats --date-span foo.laz --> 2014-09-26-11:34:22 to 2014-09-27-03:33:33 ! ;-) )
I actually only care about year and day. I'm just trying to name source folders by flight date. I can use the converter /formula from link above for today's project. However I think a date/time report would be a useful addition to pdal info for the next time anyone feels like hacking there.
Adam Steer
@adamsteer
Nov 15 2017 00:28
@maphew cool! Just be aware of leap seconds (eg https://confluence.qps.nl/display/KBE/UTC+to+GPS+Time+Correction) in GPS when converting to other time periods. to me it seems logical to leave date conversion up to the user - otherwise PDAL has to have leap second and date format logic built in.. other thoughts?
matt wilkie
@maphew
Nov 15 2017 16:42
@adamsteer thanks for looking in to it. Leap seconds? Urgh.
matt wilkie
@maphew
Nov 15 2017 16:55
Interesting. Some devices report time with leap seconds adjustment already included. (Bets on whether that fact is reliably included in metadata?) ... No worries for me, since I'm dropping time. Thanks for opening a window into a new unexplored domain.
Adam Steer
@adamsteer
Nov 15 2017 19:43

@maphew oh I’m so old fashioned, I just look up the table every time I need leap seconds and add them :) …which is still needed for that gpstime module.

note to self - include a leap second - > years dict in lidar georeferencing code, updated how? no idea yet

matt wilkie
@maphew
Nov 15 2017 22:25
re: ground classification: There are PMF and SMuRF. How to choose?
Pmf is convenient, cause there is pdal ground application for it, but smrf is newer algorithm. Is newer must be better a 'groundless' assumption? {heheh}
matt wilkie
@maphew
Nov 15 2017 23:12
doc error? "type":"reprojection", should be "type": "filters.reprojection",, yes?
matt wilkie
@maphew
Nov 15 2017 23:47
#1725 pdal translate --json seems to broken on windows