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Lidar GPS times not displaying enough precision

JJKJJK Global Mapper UserPosts: 11Trusted User
edited April 2014 in Elevation Data

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?

- John


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