[Liblas-devel] Squeeze me

[Black, Michael (IS)]

Actually, what is the "spatial order" of data that is tilted due to a non-0/90/180/270-degree flight path?
What you really need is a spatial lookup -- not spatial ordering....there is no such thing as "spatial ordering" unless you'lre talking  about sorting just along one axis (x,y, or z).
 
The LIDAR guys aren't polite enough to collect perfectly aligned lat/lon routes.
 
If you want to be able to easily do spatial queries try using SQLITE and turn on the RTree.  An RTree is kind of a waste for a fully populated LIDAR cloud but it should work just fine.
http://www.sqlite.org/
 
 
We just built our own indexer so we could say "give me all points within N meters of here" rather than using an RTree or such.
 
 
 
Michael D. Black
Senior Scientist
Northrop Grumman Mission Systems
 

________________________________

From: liblas-devel-bounces at lists.osgeo.org on behalf of Hamish
Sent: Mon 3/8/2010 5:27 PM
To: Liblas-devel at lists.osgeo.org; Etienne Bellemare Racine
Subject: Re: [Liblas-devel] Squeeze me



Etienne wrote:
> I was wondering if it would be possible, to add an option to also
> order the points coordinates in a spatial order instead of
> (I think) a temporal one, it would be much faster to scan
> the file that way to extract any point. within a given
> coordinate. Would it enter in the laszip specifications ? Of
> course, it would be much slower to write, I know, but it
> would be for a longtime gain in speed of reading. What do
> you think ?

I have no problem with optional switches, but realize that this
is a lossy operation, there is useful info in the temporal order.
e.g. if some glitch makes the nav go wonky for 5 minutes or
calibration drifts with time (eg temperature), you can filter
it out if still stored in sequential order.


regards,
Hamish



     
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