[Liblas-devel] Number of points by return

[Kollasch, Pete [DNR]]

That rule is fully consistent with my understanding of how LiDAR data
works.

The only reason I would hesitate to assume it as a rule would be if
making the assumption would cause reading data from a broken data set to
fail.  If using the assumption causes a failure to read an inconsistent
dataset, that's not very robust.

Pete Kollasch
Iowa Department of Natural Resources



-----Original Message-----
From: liblas-devel-bounces at mail.hobu.net
[mailto:liblas-devel-bounces at mail.hobu.net] On Behalf Of Mateusz Loskot
Sent: Tuesday, January 01, 2008 11:09 AM
To: liblas-devel at mail.hobu.net
Subject: [Liblas-devel] Number of points by return

Hi,

One of the LAS file header members is array of "number of points by
return". The LAS 1.x specifications do explain it in a few short
sentences and a few details are not clear to me, especially about
requirements/conditions.

Is it correct to assume that total of values of "number of points by
return" must be equal to "number of point records" ?

Simple tests seem to give answer Yes, for example:

number of point records: 213093
number of points by return: 128621, 84472, 0, 0

128621 + 84472 + 0 + 0 = 213093

Is it safe to assume it as a rule or not?

Cheers
-- 
Mateusz Loskot
http://mateusz.loskot.net
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