[postgis-users] postgis-users Digest, Vol 196, Issue 8

Thu Jun 14 05:51:30 PDT 2018

Thank you Raul that was the issue! Need to find a different algorithm or approach for generating my dot density map tiles.

Sent from my iPad

> On Jun 13, 2018, at 3:00 PM, postgis-users-request at lists.osgeo.org wrote:
> 
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> Today's Topics:
> 
>   1. Clarification ST_AsMVTGEOM on Multipoint Geometry (David Krett)
>   2. Re: Clarification ST_AsMVTGEOM on Multipoint    Geometry
>      (Raúl Marín Rodríguez)
>   3. raster operations (David Haynes)
>   4. Re: raster operations (Regina Obe)
> 
> 
> ----------------------------------------------------------------------
> 
> Message: 1
> Date: Tue, 12 Jun 2018 19:06:40 -0400
> From: David Krett <dbkrett at gmail.com>
> To: postgis-users at lists.osgeo.org
> Subject: [postgis-users] Clarification ST_AsMVTGEOM on Multipoint
>    Geometry
> Message-ID: <77010993-F328-42D1-B740-CC578480BABD at gmail.com>
> Content-Type: text/plain;    charset=us-ascii
> 
> Hopefully someone can point me in the direction, 
> 
> I am currently using Postgresql 10 with the latest stable version of postgis and serving Tiles from a table in my DB. The geometry column is comprised of Multipoint Features, and not withstanding rows contain multiple points  only 1 point is being plotted on the Vector Tiles generated for each geographic area. Tried finding documentation re this but really couldnt find much.. So could a fellow user confirm whether there are any restrictions working with multipoint geometries are whether I am encountering a bug.
> 
> Many Thanks,
> 
> David Krett
> 
> ------------------------------
> 
> Message: 2
> Date: Wed, 13 Jun 2018 09:51:56 +0200
> From: Raúl Marín Rodríguez <rmrodriguez at carto.com>
> To: PostGIS Users Discussion <postgis-users at lists.osgeo.org>
> Subject: Re: [postgis-users] Clarification ST_AsMVTGEOM on Multipoint
>    Geometry
> Message-ID:
>    <CAM6_UM4Db39J8qkUo6i585kKVc7VZ0Hovny2f5o+pXMq3FwZPQ at mail.gmail.com>
> Content-Type: text/plain; charset="utf-8"
> 
> Hi David,
> 
> ST_AsMVTGeom will remove any duplicated points if they have the same
> coordinates after switching to tile coordinates. Can you check the output
> of using it on one of your rows?
> 
> SELECT ST_ASText(ST_AsMVTGeom(ST_GeomFromText('MULTIPOINT(25 17, 26 18)'),
> 
>       ST_MakeBox2D(ST_Point(0, 0), ST_Point(4096, 4096)), 4096, 0,
> false));
>         st_astext
> -----------------------------
> MULTIPOINT(25 4079,26 4078)
> (1 row)
> 
> 
>> On Wed, Jun 13, 2018 at 1:06 AM, David Krett <dbkrett at gmail.com> wrote:
>> 
>> Hopefully someone can point me in the direction,
>> 
>> I am currently using Postgresql 10 with the latest stable version of
>> postgis and serving Tiles from a table in my DB. The geometry column is
>> comprised of Multipoint Features, and not withstanding rows contain
>> multiple points  only 1 point is being plotted on the Vector Tiles
>> generated for each geographic area. Tried finding documentation re this but
>> really couldnt find much.. So could a fellow user confirm whether there are
>> any restrictions working with multipoint geometries are whether I am
>> encountering a bug.
>> 
>> Many Thanks,
>> 
>> David Krett
>> _______________________________________________
>> postgis-users mailing list
>> postgis-users at lists.osgeo.org
>> https://lists.osgeo.org/mailman/listinfo/postgis-users
> 
> 
> 
> 
> -- 
> 
> *Raúl Marín Rodríguez *carto.com
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> ------------------------------
> 
> Message: 3
> Date: Wed, 13 Jun 2018 11:56:29 -0500
> From: David Haynes <haynesd2 at gmail.com>
> To: postgis-users at lists.osgeo.org
> Subject: [postgis-users] raster operations
> Message-ID:
>    <CAM4C04qZoOaM2b3Z8ZjwBqP=nuxqfMjLC_tVK1s1bj++BKpa2w at mail.gmail.com>
> Content-Type: text/plain; charset="utf-8"
> 
> I have a question about how to focal operations for raster statistics are
> working. I started off comparing the old depreciated
> function st_mapalgebrafctngb with the current version st_mapalgebra. The
> difference I have determined is that the st_mapalgebrafctngb will pass the
> call back function to the raster dataset similar to the st_mapalgebra, but
> as the function approaches the edge of the raster tile things get wonky.
> What are values that are assigned to pixels that do not have sufficient
> neighbors? When I run this bit of code. The ST_Value function reports that
> no values have been assigned. I assume this can be remedied by adding
> information through userargs.
> 
> with smoothed_raster as
> (
> SELECT st_mapalgebrafctngb(rast, 1, NULL, 1, 1, 'st_mean4ma(double
> precision[][][],text,text[])'::regprocedure, 'ignore', NULL) as rast
> FROM glc2000_clipped_250 r
> WHERE r.rid = 25
> ), original_raster as
> (
> SELECT r.rast
> FROM glc2000_clipped_250 r
> WHERE r.rid = 25
> )
> SELECT x, y, ST_Value(s.rast, x,y) as smoothed, ST_Value(o.rast, x,y) as
> original
> FROM smoothed_raster s, original_raster o
> CROSS JOIN generate_series(1,10) as x
> CROSS JOIN generate_series(1,10) as y
> 
> This leads me to a larger question regarding focal analysis functions for
> raster datasets. Do these functions cross the tiles? Assume you have 9
> tiles and each tile is composed of 3x3 pixels. Tiles 1-3 in row 1, 4-6 row
> 2 etc. If you have a neighborhood analysis function performing on tile 5.
> Will it grab adjacent pixels in tile 6? Unfortunately the examples I
> created returned with the same result.
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> 
> ------------------------------
> 
> Message: 4
> Date: Wed, 13 Jun 2018 13:29:52 -0400
> From: "Regina Obe" <lr at pcorp.us>
> To: "'PostGIS Users Discussion'" <postgis-users at lists.osgeo.org>
> Subject: Re: [postgis-users] raster operations
> Message-ID: <000001d4033c$23b9fea0$6b2dfbe0$@pcorp.us>
> Content-Type: text/plain; charset="utf-8"
> 
> It doesn't grab adjacent tiles.  To consider adjacent tiles you'd need to use ST_Union to stitch together multiple tiles.
> 
> 
> 
> From: postgis-users [mailto:postgis-users-bounces at lists.osgeo.org] On Behalf Of David Haynes
> Sent: Wednesday, June 13, 2018 12:56 PM
> To: postgis-users at lists.osgeo.org
> Subject: [postgis-users] raster operations
> 
> 
> 
> I have a question about how to focal operations for raster statistics are working. I started off comparing the old depreciated function st_mapalgebrafctngb with the current version st_mapalgebra. The difference I have determined is that the st_mapalgebrafctngb will pass the call back function to the raster dataset similar to the st_mapalgebra, but as the function approaches the edge of the raster tile things get wonky. What are values that are assigned to pixels that do not have sufficient neighbors? When I run this bit of code. The ST_Value function reports that no values have been assigned. I assume this can be remedied by adding information through userargs.
> 
> 
> 
> with smoothed_raster as
> 
> (
> 
> SELECT st_mapalgebrafctngb(rast, 1, NULL, 1, 1, 'st_mean4ma(double precision[][][],text,text[])'::regprocedure, 'ignore', NULL) as rast
> 
> FROM glc2000_clipped_250 r
> 
> WHERE r.rid = 25
> 
> ), original_raster as
> 
> (
> 
> SELECT r.rast
> 
> FROM glc2000_clipped_250 r
> 
> WHERE r.rid = 25
> 
> )
> 
> SELECT x, y, ST_Value(s.rast, x,y) as smoothed, ST_Value(o.rast, x,y) as original
> 
> FROM smoothed_raster s, original_raster o
> 
> CROSS JOIN generate_series(1,10) as x
> 
> CROSS JOIN generate_series(1,10) as y
> 
> 
> 
> This leads me to a larger question regarding focal analysis functions for raster datasets. Do these functions cross the tiles? Assume you have 9 tiles and each tile is composed of 3x3 pixels. Tiles 1-3 in row 1, 4-6 row 2 etc. If you have a neighborhood analysis function performing on tile 5. Will it grab adjacent pixels in tile 6? Unfortunately the examples I created returned with the same result.
> 
> 
> 
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> 
> End of postgis-users Digest, Vol 196, Issue 8
> *********************************************