Global Mapper v25.0

Lidar GPS times not displaying enough precision

JJK
JJK Global Mapper UserTrusted User
edited April 2014 in Elevation Data
Mike,

I've encountered two issues with lidar attributes in a .las file, and am wondering if they are just settings that I can tweak:

1. I'm trying to identify individual lidar returns by their unique pulses (return #1, #2, #3, #4 for pulse #1, etc.). The GPS times in our data were spec-ed to have enough precision to allow unique time-stamps for each pulse. This is confirmed by using the vendor's proprietary LAS viewer (for example, GPS time = -17990670.91966).

However, GM v 15.1.7 only displays one place to the right of the decimal (-17990670.9 -- see attached image #1), which isn't enough precision to identify unique times. This low precision is carried through when exporting the .las points to a shapefile or another .las file. It is also displayed in the search dialog (see attached #2). Is there a way to show and use the full value precision?

2. While playing around with #1 above, I noticed that the attributes shown in the Feature Information tool window (see attached #1 again) do not exactly match those shown in the search window (attached #2 again). Specifically, Feature Info has both RETURN_CNT and RETURN_NUM, while Search only shows RETURN_CNT. I want to search on both of these attributes, but can't. Is there a way to turn on the RETURN_NUM attribute in the Search dialog?

Thanks
- John

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