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

Pierre Racine Pierre.Racine at sbf.ulaval.ca
Thu Jul 8 09:37:41 PDT 2010


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<http://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 <pramsey at opengeo.org><mailto: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 <newskatze at riomhphost.net><mailto: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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