Lidar data into QGIS

classic Classic list List threaded Threaded
36 messages Options
12
Reply | Threaded
Open this post in threaded view
|

Lidar data into QGIS

pcav
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Hi all.
Lidar data in LAS format are increasingly widespread. Leaving aside all 3D frenzy, we
would be interested in simply displaying them in QGIS, with their useful attributes
(classification and intensity), either with a native driver or through an available
library. All the licensing issues around libLAS/LSTools are a bit obscure to me, so I
wonder if someone has already dealt with this.
Any hint would be appreciated.
Thanks in advance.
All the best.
- --
Paolo Cavallini - www.faunalia.eu
Corsi QGIS e PostGIS: http://www.faunalia.eu/training.html
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1
Comment: Using GnuPG with Icedove - http://www.enigmail.net/

iEYEARECAAYFAlLoAUQACgkQ/NedwLUzIr4zpgCePUoYkVf+xtWE5n0GNskWL256
0S4An34ARAD3dTfyktHatc9UuQeCb/sm
=3Pbv
-----END PGP SIGNATURE-----
_______________________________________________
Qgis-developer mailing list
[hidden email]
http://lists.osgeo.org/mailman/listinfo/qgis-developer
Reply | Threaded
Open this post in threaded view
|

Re: Lidar data into QGIS

Larry_S
Hi Paolo,


On Tue, Jan 28, 2014 at 12:13 PM, Paolo Cavallini <[hidden email]> wrote:
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Hi all.
Lidar data in LAS format are increasingly widespread. Leaving aside all 3D frenzy, we
would be interested in simply displaying them in QGIS, with their useful attributes
(classification and intensity), either with a native driver or through an available
library. All the licensing issues around libLAS/LSTools are a bit obscure to me, so I
wonder if someone has already dealt with this.
Any hint would be appreciated.

Have you looked into PDAL [0][1]? It is already in OSGeo4W 32-bit, though apparently not in 64-bit yet [2][3]. On the Mac side, it is already available in the Homebrew package manager [4]. It appears to be BSD 3-Clause licensed.

Not entirely sure of its full API, but seems to be an ideal candidate for a Processing provider, yes?

While I am not a Lidar guru by any means, it looks like the JSON output from PDAL [5] is also an input for three.js [6], e.g. Qgis2threejs PyQGIS plugin. So that is fairly interesting... may be possible to load in a clipped .las file and visualize your map canvas on it? That would be very cool.
Regards,

Larry
 
Thanks in advance.
All the best.
- --
Paolo Cavallini - www.faunalia.eu
Corsi QGIS e PostGIS: http://www.faunalia.eu/training.html
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1
Comment: Using GnuPG with Icedove - http://www.enigmail.net/

iEYEARECAAYFAlLoAUQACgkQ/NedwLUzIr4zpgCePUoYkVf+xtWE5n0GNskWL256
0S4An34ARAD3dTfyktHatc9UuQeCb/sm
=3Pbv
-----END PGP SIGNATURE-----
_______________________________________________
Qgis-developer mailing list
[hidden email]
http://lists.osgeo.org/mailman/listinfo/qgis-developer


_______________________________________________
Qgis-developer mailing list
[hidden email]
http://lists.osgeo.org/mailman/listinfo/qgis-developer
Reply | Threaded
Open this post in threaded view
|

Re: Lidar data into QGIS

pcav
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Il 29/01/2014 02:41, Larry Shaffer ha scritto:

>> Have you looked into PDAL [0][1]? It is already in OSGeo4W 32-bit, though apparently
>> not in 64-bit yet [2][3]. On the Mac side, it is already available in the Homebrew
>> package manager [4]. It appears to be BSD 3-Clause licensed.
>
>> Not entirely sure of its full API, but seems to be an ideal candidate for a
>> Processing provider, yes?

Thanks a lot Larry. PDAL is certainly interesting, as it is used and supported by
PostGIS [0]. Unfortunately is not (yet?) available on Debian-based OSs, but I guess
this can change. What would be good is, rather than (or in addition to) a Processing
provider, a data provider. I guess this should be developed from scratch, right?
All the best.

[0] http://boundlessgeo.com/2013/11/manage-lidar-postgis/
- --
Paolo Cavallini - www.faunalia.eu
Corsi QGIS e PostGIS: http://www.faunalia.eu/training.html
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1
Comment: Using GnuPG with Icedove - http://www.enigmail.net/

iEYEARECAAYFAlLootoACgkQ/NedwLUzIr4QYACfbYb1U5mZ23HXpQfwKPa5CQ5w
APgAn01fQKYgTJ42Pk46UXTc/acOK6Hc
=4JIg
-----END PGP SIGNATURE-----
_______________________________________________
Qgis-developer mailing list
[hidden email]
http://lists.osgeo.org/mailman/listinfo/qgis-developer
Reply | Threaded
Open this post in threaded view
|

Re: Lidar data into QGIS

Alexander Bruy
In reply to this post by pcav
Hi,

if I'm not wrong last year we have proposal for GSoC project with goal
to add native support for LAS data to QGIS [0]. Unfortunately this project
was not accepted.

Maybe we can found contacts of the author of this proposal and look
if he available for help?

[0] https://www.google-melange.com/gsoc/proposal/review/google/gsoc2013/qgis_lidar/1

2014-01-28 Paolo Cavallini <[hidden email]>:

> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> Hi all.
> Lidar data in LAS format are increasingly widespread. Leaving aside all 3D frenzy, we
> would be interested in simply displaying them in QGIS, with their useful attributes
> (classification and intensity), either with a native driver or through an available
> library. All the licensing issues around libLAS/LSTools are a bit obscure to me, so I
> wonder if someone has already dealt with this.
> Any hint would be appreciated.
> Thanks in advance.
> All the best.
> - --
> Paolo Cavallini - www.faunalia.eu
> Corsi QGIS e PostGIS: http://www.faunalia.eu/training.html
> -----BEGIN PGP SIGNATURE-----
> Version: GnuPG v1
> Comment: Using GnuPG with Icedove - http://www.enigmail.net/
>
> iEYEARECAAYFAlLoAUQACgkQ/NedwLUzIr4zpgCePUoYkVf+xtWE5n0GNskWL256
> 0S4An34ARAD3dTfyktHatc9UuQeCb/sm
> =3Pbv
> -----END PGP SIGNATURE-----
> _______________________________________________
> Qgis-developer mailing list
> [hidden email]
> http://lists.osgeo.org/mailman/listinfo/qgis-developer



--
Alexander Bruy
_______________________________________________
Qgis-developer mailing list
[hidden email]
http://lists.osgeo.org/mailman/listinfo/qgis-developer
Reply | Threaded
Open this post in threaded view
|

Lidar data into QGIS

3nids
In reply to this post by pcav
Hi Paolo,

This would probably be quite a different way of dealing with the data source. I suppose the idea would be to fetch all the points at once and store them in a kd-tree. Otherwise, refreshing the canvas would take ages to refresh.

The laslib [0,1] (from lastools) is LGPL.

But there is also liblas [2] which is available on Osgeo4W and has debian packages.
The code is on github [3], there is the licence info:

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following
conditions are met....

Cheers,

Denis


[0] http://www.cs.unc.edu/~isenburg/lastools/
[1] http://www.cs.unc.edu/~isenburg/lastools/download/laslib.zip
[2] http://www.liblas.org/
[3] https://github.com/libLAS/libLAS

_______________________________________________
Qgis-developer mailing list
[hidden email]
http://lists.osgeo.org/mailman/listinfo/qgis-developer
Reply | Threaded
Open this post in threaded view
|

Re: Lidar data into QGIS

pcav
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Il 29/01/2014 09:01, Denis Rouzaud ha scritto:

> This would probably be quite a different way of dealing with the data source. I
> suppose the idea would be to fetch all the points at once and store them in a
> kd-tree. Otherwise, refreshing the canvas would take ages to refresh.
>
> The laslib [0,1] (from lastools) is LGPL.
>
> But there is also liblas [2] which is available on Osgeo4W and has debian packages.
> The code is on github [3], there is the licence info:

Hi all,
thanks for following up. Of course we need some smart way to deal with such huge
amounts of points (that's why I think we need a brand new provider). libLAS and PDAL
seem to overlap, and at least one developer is involved in both: does anybody know
why, and which one would be better to use?
All the best.
- --
Paolo Cavallini - www.faunalia.eu
Corsi QGIS e PostGIS: http://www.faunalia.eu/training.html
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1
Comment: Using GnuPG with Icedove - http://www.enigmail.net/

iEYEARECAAYFAlLott4ACgkQ/NedwLUzIr7pGgCdGbScG2y2DPMzchGVwggrYqAN
RbUAn3aBhtu/nwst8ceQT+POgfHyHckt
=GXBE
-----END PGP SIGNATURE-----
_______________________________________________
Qgis-developer mailing list
[hidden email]
http://lists.osgeo.org/mailman/listinfo/qgis-developer
Reply | Threaded
Open this post in threaded view
|

Re: Lidar data into QGIS

Jean-Roc Morreale
Le 2014-01-29 09:07, Paolo Cavallini a écrit :
> Hi all,
> thanks for following up. Of course we need some smart way to deal with
> such huge
> amounts of points (that's why I think we need a brand new provider).
> libLAS and PDAL
> seem to overlap, and at least one developer is involved in both: does
> anybody know
> why, and which one would be better to use?
> All the best.

if I'm not wrong, pdal is the successor of liblas as it is meant to
access more file format and provide the same set of functionalities than
gdal.

Other interesting tools and libs are PCL, CLoudCompare, SPDLib/Viewer
_______________________________________________
Qgis-developer mailing list
[hidden email]
http://lists.osgeo.org/mailman/listinfo/qgis-developer
Reply | Threaded
Open this post in threaded view
|

Re: Lidar data into QGIS

Etienne Tourigny-3
In reply to this post by pcav
There was some discussion about LAS format and PDAL on the GDAL mailing list a few weeks ago, there is probably some interesting info there.

cheers
Etienne


On Tue, Jan 28, 2014 at 5:13 PM, Paolo Cavallini <[hidden email]> wrote:
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Hi all.
Lidar data in LAS format are increasingly widespread. Leaving aside all 3D frenzy, we
would be interested in simply displaying them in QGIS, with their useful attributes
(classification and intensity), either with a native driver or through an available
library. All the licensing issues around libLAS/LSTools are a bit obscure to me, so I
wonder if someone has already dealt with this.
Any hint would be appreciated.
Thanks in advance.
All the best.
- --
Paolo Cavallini - www.faunalia.eu
Corsi QGIS e PostGIS: http://www.faunalia.eu/training.html
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1
Comment: Using GnuPG with Icedove - http://www.enigmail.net/

iEYEARECAAYFAlLoAUQACgkQ/NedwLUzIr4zpgCePUoYkVf+xtWE5n0GNskWL256
0S4An34ARAD3dTfyktHatc9UuQeCb/sm
=3Pbv
-----END PGP SIGNATURE-----
_______________________________________________
Qgis-developer mailing list
[hidden email]
http://lists.osgeo.org/mailman/listinfo/qgis-developer


_______________________________________________
Qgis-developer mailing list
[hidden email]
http://lists.osgeo.org/mailman/listinfo/qgis-developer
Reply | Threaded
Open this post in threaded view
|

Re: Lidar data into QGIS

pcav
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Il 29/01/2014 11:37, Etienne Tourigny ha scritto:
> There was some discussion about LAS format and PDAL on the GDAL mailing list a few
> weeks ago, there is probably some interesting info there.

I suppose you mean:
http://lists.osgeo.org/pipermail/gdal-dev/2013-November/037613.html
So the idea is writing an OGR driver for PDAL.
Still unsure if the result would be usable in QGIS, for performance reasons.
Anyway, the indication seems to go with PDAL rather than libLAS, good to know.
Thanks a lot.
- --
Paolo Cavallini - www.faunalia.eu
Corsi QGIS e PostGIS: http://www.faunalia.eu/training.html
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1
Comment: Using GnuPG with Icedove - http://www.enigmail.net/

iEYEARECAAYFAlLo250ACgkQ/NedwLUzIr5h/wCcCJ5atUj0jgppSgnAX0b4Z+hN
NGoAniAQF9AHZvpOBq7zX+x+VKbxPWXf
=uuo4
-----END PGP SIGNATURE-----
_______________________________________________
Qgis-developer mailing list
[hidden email]
http://lists.osgeo.org/mailman/listinfo/qgis-developer
Reply | Threaded
Open this post in threaded view
|

Re: Lidar data into QGIS

A Huarte
Hi Paolo, about "performance reasons" recently we spoken about this item in other thread:

[Qgis-developer] On the fly simplication of point layer

In order to render so big layers as LAS files are, there are two strategies, discard points on renderer side, or on featureiterator side by distance proximity.

I think interesting to continue this item.
Alvaro




De: Paolo Cavallini <[hidden email]>
Para: Etienne Tourigny <[hidden email]>
CC: qgis-developer <[hidden email]>
Enviado: Miércoles 29 de enero de 2014 11:44
Asunto: Re: [Qgis-developer] Lidar data into QGIS

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Il 29/01/2014 11:37, Etienne Tourigny ha scritto:
> There was some discussion about LAS format and PDAL on the GDAL mailing list a few
> weeks ago, there is probably some interesting info there.

I suppose you mean:
http://lists.osgeo.org/pipermail/gdal-dev/2013-November/037613.html
So the idea is writing an OGR driver for PDAL.
Still unsure if the result would be usable in QGIS, for performance reasons.
Anyway, the indication seems to go with PDAL rather than libLAS, good to know.
Thanks a lot.
- --
Paolo Cavallini - www.faunalia.eu
Corsi QGIS e PostGIS: http://www.faunalia.eu/training.html
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1
Comment: Using GnuPG with Icedove - http://www.enigmail.net/

iEYEARECAAYFAlLo250ACgkQ/NedwLUzIr5h/wCcCJ5atUj0jgppSgnAX0b4Z+hN
NGoAniAQF9AHZvpOBq7zX+x+VKbxPWXf
=uuo4

-----END PGP SIGNATURE-----
_______________________________________________
Qgis-developer mailing list
[hidden email]
http://lists.osgeo.org/mailman/listinfo/qgis-developer



_______________________________________________
Qgis-developer mailing list
[hidden email]
http://lists.osgeo.org/mailman/listinfo/qgis-developer
Reply | Threaded
Open this post in threaded view
|

Re: Lidar data into QGIS

pcav
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Il 29/01/2014 12:27, A Huarte ha scritto:
> Hi Paolo, about "performance reasons" recently we spoken about this item in other thread:
>
> [Qgis-developer] On the fly simplication of point layer
>
> In order to render so big layers as LAS files are, there are two strategies, discard
> points on renderer side, or on featureiterator side by distance proximity.

Hi Alvaro,
so you suggest to use a general approach to simplification, rather than having a
specialized las provider, right?
All the best, and thanks.
- --
Paolo Cavallini - www.faunalia.eu
Corsi QGIS e PostGIS: http://www.faunalia.eu/training.html
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1
Comment: Using GnuPG with Icedove - http://www.enigmail.net/

iEYEARECAAYFAlLo6iUACgkQ/NedwLUzIr5tLgCfTQWQtojz/4iSwx6qTHThKKix
5nIAn2RDw84a62kwR/6yZssRlS+Z6JEP
=zYWd
-----END PGP SIGNATURE-----
_______________________________________________
Qgis-developer mailing list
[hidden email]
http://lists.osgeo.org/mailman/listinfo/qgis-developer
Reply | Threaded
Open this post in threaded view
|

Re: Lidar data into QGIS

A Huarte
yes, it can be implemented on renderer level (Martin Dobias propose it) or on featureiterator level similar to current simplification classes for line and polygons

I think it is pending for a test of performance
Best Regards
Alvaro


De: Paolo Cavallini <[hidden email]>
Para: A Huarte <[hidden email]>; Etienne Tourigny <[hidden email]>
CC: qgis-developer <[hidden email]>
Enviado: Miércoles 29 de enero de 2014 12:46
Asunto: Re: [Qgis-developer] Lidar data into QGIS

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Il 29/01/2014 12:27, A Huarte ha scritto:
> Hi Paolo, about "performance reasons" recently we spoken about this item in other thread:
>
> [Qgis-developer] On the fly simplication of point layer
>
> In order to render so big layers as LAS files are, there are two strategies, discard
> points on renderer side, or on featureiterator side by distance proximity.

Hi Alvaro,
so you suggest to use a general approach to simplification, rather than having a
specialized las provider, right?
All the best, and thanks.
- --
Paolo Cavallini - www.faunalia.eu
Corsi QGIS e PostGIS: http://www.faunalia.eu/training.html
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1
Comment: Using GnuPG with Icedove - http://www.enigmail.net/

iEYEARECAAYFAlLo6iUACgkQ/NedwLUzIr5tLgCfTQWQtojz/4iSwx6qTHThKKix
5nIAn2RDw84a62kwR/6yZssRlS+Z6JEP
=zYWd

-----END PGP SIGNATURE-----



_______________________________________________
Qgis-developer mailing list
[hidden email]
http://lists.osgeo.org/mailman/listinfo/qgis-developer
Reply | Threaded
Open this post in threaded view
|

Re: Lidar data into QGIS

Jean-Roc Morreale
Can it performs fast enough to display hundred millions points or
billions at once ? Does it leverage a quadtree approach ?

Le 2014-01-29 12:55, A Huarte a écrit :
> yes, it can be implemented on renderer level (Martin Dobias propose
> it) or on featureiterator level similar to current simplification
> classes for line and polygons
>
> I think it is pending for a test of performance
> Best Regards
> Alvaro


_______________________________________________
Qgis-developer mailing list
[hidden email]
http://lists.osgeo.org/mailman/listinfo/qgis-developer
Reply | Threaded
Open this post in threaded view
|

Re: Lidar data into QGIS

A Huarte
I think but using a quadtree approach there is a problem, and it is none other than the construction of the quadtree itself for so big data.

IMHO I would use a specific provider (with a specific featureiterator) reading sequentially the LAS file and discarding points before fetch it to renderer using the RectangleFilter of current FeatureRequest. It avoid create many-many QgsFeature's that after are discarded in renderer side.

I use this technique in a personal viewer, and after first read of file (the file is cached in SO), the following drawings are quite fast.

Alvaro


De: Jean-Roc Morreale <[hidden email]>
Para: [hidden email]
Enviado: Miércoles 29 de enero de 2014 13:32
Asunto: Re: [Qgis-developer] Lidar data into QGIS

Can it performs fast enough to display hundred millions points or
billions at once ? Does it leverage a quadtree approach ?

Le 2014-01-29 12:55, A Huarte a écrit :
> yes, it can be implemented on renderer level (Martin Dobias propose
> it) or on featureiterator level similar to current simplification
> classes for line and polygons
>
> I think it is pending for a test of performance
> Best Regards
> Alvaro


_______________________________________________
Qgis-developer mailing list
[hidden email]
http://lists.osgeo.org/mailman/listinfo/qgis-developer



_______________________________________________
Qgis-developer mailing list
[hidden email]
http://lists.osgeo.org/mailman/listinfo/qgis-developer
Reply | Threaded
Open this post in threaded view
|

Re: Lidar data into QGIS

Martin Dobias
In reply to this post by A Huarte
On Wed, Jan 29, 2014 at 6:55 PM, A Huarte <[hidden email]> wrote:
> yes, it can be implemented on renderer level (Martin Dobias propose it) or
> on featureiterator level similar to current simplification classes for line
> and polygons

Personally I do not think we can treat lidar data like with ordinary
vector layer. Using vector layer for point clouds seems like trying to
represent raster data as vector layer with square polygon per raster
cell - it is possible, but very sub-optimal. Also, lots of
functionality in vector layers does not make much sense for point
clouds. I believe the right approach would be to create a new type of
map layer and handle everything there. For a proof of concept, it
could be a new "plugin" layer type.

Regards
Martin
_______________________________________________
Qgis-developer mailing list
[hidden email]
http://lists.osgeo.org/mailman/listinfo/qgis-developer
Reply | Threaded
Open this post in threaded view
|

Re: Lidar data into QGIS

A Huarte
I agree, 

http://www.fugroviewer.com/
can be our target ?

Alvaro


De: Martin Dobias <[hidden email]>
Para: A Huarte <[hidden email]>
CC: "[hidden email]" <[hidden email]>; Etienne Tourigny <[hidden email]>; qgis-developer <[hidden email]>
Enviado: Miércoles 29 de enero de 2014 14:04
Asunto: Re: [Qgis-developer] Lidar data into QGIS

On Wed, Jan 29, 2014 at 6:55 PM, A Huarte <[hidden email]> wrote:
> yes, it can be implemented on renderer level (Martin Dobias propose it) or
> on featureiterator level similar to current simplification classes for line
> and polygons

Personally I do not think we can treat lidar data like with ordinary
vector layer. Using vector layer for point clouds seems like trying to
represent raster data as vector layer with square polygon per raster
cell - it is possible, but very sub-optimal. Also, lots of
functionality in vector layers does not make much sense for point
clouds. I believe the right approach would be to create a new type of
map layer and handle everything there. For a proof of concept, it
could be a new "plugin" layer type.

Regards

Martin



_______________________________________________
Qgis-developer mailing list
[hidden email]
http://lists.osgeo.org/mailman/listinfo/qgis-developer
Reply | Threaded
Open this post in threaded view
|

Re: Lidar data into QGIS

Jean-Roc Morreale
In reply to this post by A Huarte
Most lidar files are not spatially ordered so with a sequential read you
will end up reading the whole file, it's like accessing a untiled
unpyramided bigtiff : painful.

Le 2014-01-29 13:52, A Huarte a écrit :

> I think but using a quadtree approach there is a problem, and it is
> none other than the construction of the quadtree itself for so big
> data.
>
> IMHO I would use a specific provider (with a specific featureiterator)
> reading sequentially the LAS file and discarding points before fetch
> it to renderer using the RectangleFilter of current FeatureRequest. It
> avoid create many-many QgsFeature's that after are discarded in
> renderer side.
>
> I use this technique in a personal viewer, and after first read of
> file (the file is cached in SO), the following drawings are quite
> fast.
>
> Alvaro
>
>> -------------------------
>> DE: Jean-Roc Morreale <[hidden email]>
>> PARA: [hidden email]
>> ENVIADO: Miércoles 29 de enero de 2014 13:32
>> ASUNTO: Re: [Qgis-developer] Lidar data into QGIS
>>
>> Can it performs fast enough to display hundred millions points or
>> billions at once ? Does it leverage a quadtree approach ?
>>
>> Le 2014-01-29 12:55, A Huarte a écrit :
>>> yes, it can be implemented on renderer level (Martin Dobias
>> propose
>>> it) or on featureiterator level similar to current simplification
>>> classes for line and polygons
>>>
>>> I think it is pending for a test of performance
>>> Best Regards
>>> Alvaro
>>
>> _______________________________________________
>> Qgis-developer mailing list
>> [hidden email]
>> http://lists.osgeo.org/mailman/listinfo/qgis-developer [1]
>
>
>
> Links:
> ------
> [1] http://lists.osgeo.org/mailman/listinfo/qgis-developer
_______________________________________________
Qgis-developer mailing list
[hidden email]
http://lists.osgeo.org/mailman/listinfo/qgis-developer
Reply | Threaded
Open this post in threaded view
|

Re: Lidar data into QGIS

Randal Hale
Would LASTools add anything to the conversation? I do believe they
re-order the file (but I've not used it).


-----------------
Randal Hale, GISP
North River Geographic Systems, Inc
http://www.northrivergeographic.com
423.653.3611 [hidden email]
<mailto:[hidden email]>
twitter:rjhale
http://about.me/rjhale

On 01/29/2014 08:25 AM, Jean-Roc Morreale wrote:

> Most lidar files are not spatially ordered so with a sequential read
> you will end up reading the whole file, it's like accessing a untiled
> unpyramided bigtiff : painful.
>
> Le 2014-01-29 13:52, A Huarte a écrit :
>> I think but using a quadtree approach there is a problem, and it is
>> none other than the construction of the quadtree itself for so big
>> data.
>>
>> IMHO I would use a specific provider (with a specific featureiterator)
>> reading sequentially the LAS file and discarding points before fetch
>> it to renderer using the RectangleFilter of current FeatureRequest. It
>> avoid create many-many QgsFeature's that after are discarded in
>> renderer side.
>>
>> I use this technique in a personal viewer, and after first read of
>> file (the file is cached in SO), the following drawings are quite
>> fast.
>>
>> Alvaro
>>
>>> -------------------------
>>> DE: Jean-Roc Morreale <[hidden email]>
>>> PARA: [hidden email]
>>> ENVIADO: Miércoles 29 de enero de 2014 13:32
>>> ASUNTO: Re: [Qgis-developer] Lidar data into QGIS
>>>
>>> Can it performs fast enough to display hundred millions points or
>>> billions at once ? Does it leverage a quadtree approach ?
>>>
>>> Le 2014-01-29 12:55, A Huarte a écrit :
>>>> yes, it can be implemented on renderer level (Martin Dobias
>>> propose
>>>> it) or on featureiterator level similar to current simplification
>>>> classes for line and polygons
>>>>
>>>> I think it is pending for a test of performance
>>>> Best Regards
>>>> Alvaro
>>>
>>> _______________________________________________
>>> Qgis-developer mailing list
>>> [hidden email]
>>> http://lists.osgeo.org/mailman/listinfo/qgis-developer [1]
>>
>>
>>
>> Links:
>> ------
>> [1] http://lists.osgeo.org/mailman/listinfo/qgis-developer
> _______________________________________________
> Qgis-developer mailing list
> [hidden email]
> http://lists.osgeo.org/mailman/listinfo/qgis-developer

_______________________________________________
Qgis-developer mailing list
[hidden email]
http://lists.osgeo.org/mailman/listinfo/qgis-developer
Reply | Threaded
Open this post in threaded view
|

Re: Lidar data into QGIS

A Huarte
In reply to this post by Jean-Roc Morreale
You are right, but only if it is possible to generate the quadtree on the fly (millions of points), or preprocess it to disk.

this doc uses a mixed strategy (I used it and it works fine)...
http://www.cs.unc.edu/~isenburg/papers/ilss-scdt-06.pdf

a first pass read the file to build a special quadtree which only save the number of points of each quad-item.
when the data is readed, it accumulates the points, and when a quad-item has all points, then it returns a releases the buffer of this quad-item.

Alvaro


De: Jean-Roc Morreale <[hidden email]>
Para: A Huarte <[hidden email]>
CC: [hidden email]
Enviado: Miércoles 29 de enero de 2014 14:25
Asunto: Re: [Qgis-developer] Lidar data into QGIS

Most lidar files are not spatially ordered so with a sequential read you
will end up reading the whole file, it's like accessing a untiled
unpyramided bigtiff : painful.

Le 2014-01-29 13:52, A Huarte a écrit :

> I think but using a quadtree approach there is a problem, and it is
> none other than the construction of the quadtree itself for so big
> data.
>
> IMHO I would use a specific provider (with a specific featureiterator)
> reading sequentially the LAS file and discarding points before fetch
> it to renderer using the RectangleFilter of current FeatureRequest. It
> avoid create many-many QgsFeature's that after are discarded in
> renderer side.
>
> I use this technique in a personal viewer, and after first read of
> file (the file is cached in SO), the following drawings are quite
> fast.
>
> Alvaro
>
>> -------------------------
>> DE: Jean-Roc Morreale <[hidden email]>
>> PARA: [hidden email]
>> ENVIADO: Miércoles 29 de enero de 2014 13:32
>> ASUNTO: Re: [Qgis-developer] Lidar data into QGIS
>>
>> Can it performs fast enough to display hundred millions points or
>> billions at once ? Does it leverage a quadtree approach ?
>>
>> Le 2014-01-29 12:55, A Huarte a écrit :
>>> yes, it can be implemented on renderer level (Martin Dobias
>> propose
>>> it) or on featureiterator level similar to current simplification
>>> classes for line and polygons
>>>
>>> I think it is pending for a test of performance
>>> Best Regards
>>> Alvaro
>>
>> _______________________________________________
>> Qgis-developer mailing list
>> [hidden email]
>> http://lists.osgeo.org/mailman/listinfo/qgis-developer [1]
>
>
>
> Links:


_______________________________________________
Qgis-developer mailing list
[hidden email]
http://lists.osgeo.org/mailman/listinfo/qgis-developer
Reply | Threaded
Open this post in threaded view
|

Re: Lidar data into QGIS

A Huarte
In reply to this post by Randal Hale
But then we must preprocess the data before load it in QGIS


De: Randal Hale <[hidden email]>
Para: [hidden email]
Enviado: Miércoles 29 de enero de 2014 14:49
Asunto: Re: [Qgis-developer] Lidar data into QGIS

Would LASTools add anything to the conversation? I do believe they
re-order the file (but I've not used it).


-----------------
Randal Hale, GISP
North River Geographic Systems, Inc
http://www.northrivergeographic.com
423.653.3611 [hidden email]
<mailto:[hidden email]>
twitter:rjhale
http://about.me/rjhale

On 01/29/2014 08:25 AM, Jean-Roc Morreale wrote:

> Most lidar files are not spatially ordered so with a sequential read
> you will end up reading the whole file, it's like accessing a untiled
> unpyramided bigtiff : painful.
>
> Le 2014-01-29 13:52, A Huarte a écrit :
>> I think but using a quadtree approach there is a problem, and it is
>> none other than the construction of the quadtree itself for so big
>> data.
>>
>> IMHO I would use a specific provider (with a specific featureiterator)
>> reading sequentially the LAS file and discarding points before fetch
>> it to renderer using the RectangleFilter of current FeatureRequest. It
>> avoid create many-many QgsFeature's that after are discarded in
>> renderer side.
>>
>> I use this technique in a personal viewer, and after first read of
>> file (the file is cached in SO), the following drawings are quite
>> fast.
>>
>> Alvaro
>>
>>> -------------------------
>>> DE: Jean-Roc Morreale <[hidden email]>
>>> PARA: [hidden email]
>>> ENVIADO: Miércoles 29 de enero de 2014 13:32
>>> ASUNTO: Re: [Qgis-developer] Lidar data into QGIS
>>>
>>> Can it performs fast enough to display hundred millions points or
>>> billions at once ? Does it leverage a quadtree approach ?
>>>
>>> Le 2014-01-29 12:55, A Huarte a écrit :
>>>> yes, it can be implemented on renderer level (Martin Dobias
>>> propose
>>>> it) or on featureiterator level similar to current simplification
>>>> classes for line and polygons
>>>>
>>>> I think it is pending for a test of performance
>>>> Best Regards
>>>> Alvaro
>>>
>>> _______________________________________________
>>> Qgis-developer mailing list
>>> [hidden email]
>>> http://lists.osgeo.org/mailman/listinfo/qgis-developer [1]
>>
>>
>>
>> Links:
>> ------
>> [1] http://lists.osgeo.org/mailman/listinfo/qgis-developer
> _______________________________________________
> Qgis-developer mailing list
> [hidden email]
> http://lists.osgeo.org/mailman/listinfo/qgis-developer

_______________________________________________
Qgis-developer mailing list
[hidden email]
http://lists.osgeo.org/mailman/listinfo/qgis-developer



_______________________________________________
Qgis-developer mailing list
[hidden email]
http://lists.osgeo.org/mailman/listinfo/qgis-developer
12