[postgis-users] lidar: what is therecommended wayof storing/indexing

Thu Jul 8 16:53:16 PDT 2010

Thanks guys.  I think I understand better now the issue.  

So in some cases the resolution loss is acceptable but in most cases it is
not correct?

I'm just curious aside from pulling aerial etc. out of Lidar what use case
people would use the MG4 Lidar to raster driver for

http://trac.osgeo.org/gdal/ticket/3523

Sorry for the endless Lidar newbie questions.

Thanks,
Regina

  _____  

From: postgis-users-bounces at postgis.refractions.net
[mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of Pierre
Racine
Sent: Thursday, July 08, 2010 12:38 PM
To: PostGIS Users Discussion
Subject: Re: [postgis-users] lidar: what is therecommended wayof
storing/indexing

Regina, 

there is no real limits on the number of bands but I tend to agree with
Paul: you can convert a lidar coverage to a grid but this is a lossy
operation like converting a vector coverage to raster. The amount of
information you lose is dependent on the resolution of the target raster and
there is no perfect resolution (only 0 which is impossible).

Pierre

From: postgis-users-bounces at postgis.refractions.net
[mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of Paragon
Corporation
Sent: 8 juillet 2010 12:23
To: 'PostGIS Users Discussion'
Subject: Re: [postgis-users] lidar: what is the recommended wayof
storing/indexing

Okay since everyone is providing their suggestions, let me provide my less
than educated suggestion based on my fuzzy assumption of how Lidar is
structured.

Why don't you just use the new WKT Raster (PostGIS raster storage)?  It
allows you to store multiple bands per pixel.  I think you might even be
able to use GDAL to load the Lidar data right in ot the PostGIS raster
storage format given this bug fix.

http://trac.osgeo.org/gdal/ticket/3523

So I'm  imaging your z, range, target number, reflectance you would store as
separate raster bands.

Pierre and Jorge can correct me, but I don't think there is a limit on the
number of raster bands you can store per raster tile

http://www.postgis.org/documentation/manual-svn/RT_reference.html

With that you can do spatial intersects queries to pull out the different
band values with 

http://www.postgis.org/documentation/manual-svn/RT_ST_Intersection.html

or 

http://www.postgis.org/documentation/manual-svn/RT_ST_Value.html

The meta data function would be useful for letting you know how many bands
you have etc.

http://www.postgis.org/documentation/manual-svn/RT_ST_MetaData.html

Hope that helps,

Regina

  _____  

From: postgis-users-bounces at postgis.refractions.net
[mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of Peter
Baumann
Sent: Thursday, July 08, 2010 9:32 AM
To: PostGIS Users Discussion
Subject: Re: [postgis-users] lidar: what is the recommended wayof
storing/indexing

Indeed, a column store for arrays is usually quite ;-) inefficient.
Let me point you to the rasdaman array DBMS which plugs into PostgreSQL and
offers an optimized array query language on top. See www.rasdaman.org.

-Peter

Paul Ramsey wrote: 

Oh, actually one-row-per-point is a bad idea, because the size of
lidar sets mitigates against that. Putting them into multipoint
collections of 50 or 100 points is better. But that implies
preprocessing things a bit to find good patches. In generally, there's
a lot of tooling needed to do this well, I fear.

P

On Thu, Jul 8, 2010 at 6:27 AM, Paul Ramsey  <mailto:pramsey at opengeo.org>
<pramsey at opengeo.org> wrote:

There is no recommended way right now. It's a core development
activity I'd love to have funded... :)

http://opengeo.org/products/coredevelopment/postgis/pointclouds/

In the meanwhile a approach might be to put the x/y/z into a postgis
geometry and stuff the rest of the data into an array of doubles in
another column. Your app would need to know which array element was
which kind of data, but you'd still have it all available.

P.

On Thu, Jul 8, 2010 at 2:53 AM, Biddy  <mailto:newskatze at riomhphost.net>
<newskatze at riomhphost.net> wrote:

Hi everyone,

is there a recommended way of storing lidar data in postgis?

In particular, I am interested in not just storing long, lat, alt but also
keeping all the raw data (for example range, target number, reflectance,
etc.)

Regards,
B.

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-- 
Dr. Peter Baumann
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