Re: [postgis-users] Programmatically generate maps zoomed to extent of shapes?
I think it looks like a job for mapserver to produce the images. then you can decide both output extent on the fly and decide the input extent by a query or a bounding box or whatever. but that will just give you images. How to make the layout I don't know. /Nicklas2010-09-23 John Poole wrote: I'm preparing walk lists for a campaign which contains a table of addresses, about 35 to a page on 8.5 x 11 paper. I have the addresses tied into a postgis database with roads and assessor's parcels, so for a given page, I can get a handle on the IDs of the associated shapes. What I'm wondering is would it be possible to generate a map in SVG or PNG/TIFF that would measure 8 x 10.5 and be zoomed to a level that would just include the most opposite parcels. I gather I could define a shape that is all inclusive of the list of shapes for a particular page, but can I then take the coordinates or whatever information derived and submit it to a renderer which then creates a zoomed image of defined dpi (if PNG or TIFF) that would be a representation of a view of all parcels. For example, I have a list of addresses, being 35 representing 3 1/2 city blocks: 200 Main Street 204 ... 535 All of the above addresses tie into specific shape IDs in postgis. I'd like to have a map which would then display a zoomed level so that the parcel of 200 is leftmost and parcel 535 is rightmost of the image. This map would be generated on the fly without human intervention, in other words generated by script. I'm getting my feet wet with various renderers, but have not seen any that might be manipulated or controlled programmatically so that mapes could be generated by scripting. What I am envisioning is having a map of the parcels on the back side of a previous page representing an view of the current page. So, if page three (3) contains the above addresses, the back side of page two (2)would have the map showing all parcels tied to the addresses of page three. That way someone looking at the list on page three could hold up the back side of page 2 in a binder and view a map zoomed to the right level containing all the parcels referenced on page three. I'd prefer to use my own data from postgis, I think this kind of generation would be possible with the Google maps API and possibly creating a container shape that bounds all the shapes from the list. It would be helpful to learn of any renderers, especially ones that expose an application interface. (Hmmm.. now I'm thinking I could generate a large image file of certain sectors and if I could tie the pixels, I could use ImageMagick to slice and dice what I need.) Any rate, this is a wild inquiry which might garner some attention and generate some responses about renderers, especially ones with exposed APIs so they can be manipulated programmatically. -- John L. Poole P.O. Box 6566 Napa, CA 94581-6566 707-812-1323 jlpool...@gmail.com ___ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users ___ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users
Re: [postgis-users] Difference between ST_Intersects and operator
Ok. I see. But why is the results so different. When using ST_Intersects the result is correct, while using it seems there is no order in which vector grid cells it selects. It is not the cells intersecting with the country polygon, but rather a mesh of random cells also outside of the country polygons. 2010/9/22 Paragon Corporation l...@pcorp.us does a bounding box intersects check where as ST_Intersects does a more intensive actual geometry intersect check. Which is why its slower. -- *From:* postgis-users-boun...@postgis.refractions.net [mailto: postgis-users-boun...@postgis.refractions.net] *On Behalf Of *Andreas Forø Tollefsen *Sent:* Wednesday, September 22, 2010 11:00 AM *To:* PostGIS Users Discussion *Subject:* [postgis-users] Difference between ST_Intersects and operator Hi all. I am working on a huge vector grid project where i need to intersect country polygon data and vector grid cells. For this i need to first select the grid cells which intersects with the country polygons. SELECT DISTINCT testgrid.gid, xcoord, ycoord, cell INTO testgrid2 FROM testgrid, cshaperef WHERE ST_Intersects(cshaperef.the_geom, testgrid.cell)=true I tried both the ST_Intersects and the operator, but i cannot really understand the difference. After looking at my results the ST_Intersects gave exactly the cells which intersected with the country polygons, while the gave many additional cells. Another interesting observation is the the is way faster than the ST_Intersects which in my case 188 polygons and 212000 cells takes a lot of time. Could anyone please elaborate on the difference? ___ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users ___ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users
Re: [postgis-users] Difference between ST_Intersects and operator
As said before the operator only calculates which bounding boxes that intersects. The bounding box is the smallest box that can contain the geometry. It is a box made of the maximum and minimum x any y values found in the geometry. So, when the bounding boxes intersect it says nothing about if the geometries inside the box intersects. But it is a fast way to sort away geometries that NOT intersect since intersections between geometries is impossible if the bounding boxes doesn't intersect. The bounding boxes is also possible to structure in an index. That makes it really fast to find intersection between bounding boxes if you have a working index on the geometries. This is what ST_Intersects (and a lot of other functions) does. First it finds intersecting bounding boxes with help of the index if present (this is done with the operator inside ST_Intersects function). Then it checks the real geometries inside the boxes if they really intersects. HTH Nicklas On Thu, 2010-09-23 at 09:08 +0200, Andreas Forø Tollefsen wrote: Ok. I see. But why is the results so different. When using ST_Intersects the result is correct, while using it seems there is no order in which vector grid cells it selects. It is not the cells intersecting with the country polygon, but rather a mesh of random cells also outside of the country polygons. 2010/9/22 Paragon Corporation l...@pcorp.us does a bounding box intersects check where as ST_Intersects does a more intensive actual geometry intersect check. Which is why its slower. __ From: postgis-users-boun...@postgis.refractions.net [mailto:postgis-users-boun...@postgis.refractions.net] On Behalf Of Andreas Forø Tollefsen Sent: Wednesday, September 22, 2010 11:00 AM To: PostGIS Users Discussion Subject: [postgis-users] Difference between ST_Intersects and operator Hi all. I am working on a huge vector grid project where i need to intersect country polygon data and vector grid cells. For this i need to first select the grid cells which intersects with the country polygons. SELECT DISTINCT testgrid.gid, xcoord, ycoord, cell INTO testgrid2 FROM testgrid, cshaperef WHERE ST_Intersects(cshaperef.the_geom, testgrid.cell)=true I tried both the ST_Intersects and the operator, but i cannot really understand the difference. After looking at my results the ST_Intersects gave exactly the cells which intersected with the country polygons, while the gave many additional cells. Another interesting observation is the the is way faster than the ST_Intersects which in my case 188 polygons and 212000 cells takes a lot of time. Could anyone please elaborate on the difference? ___ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users ___ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users ___ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users
[postgis-users] repeating points filtering
Hi, I have a table called locations, which contains the city name's and landmarks. some of the location name get's repeated but they all have a different lat,lon. some of the locations are very near by like within 2km. I want to eliminate the locations that are very close by having the same name. (only those have the same name). distinct give's me unique record's. does buffer help me to solve the problem. i am not able to understand... i am confused which one to use. whether to use, buffer, distance or dwitin. -Nicholas I ___ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users
[postgis-users] Geography type
Sorry for my english. I would like to know the use of the geographic data type. Actually i have to work in represent spherical data. Thanks. Gaston Lucero www.sitrack.com Disclaimer: This email and any attachments thereof may contain confidential, privileged, proprietary, or otherwise private information. This email is intended solely for the use of the individual to whom it is addressed. If you are not the intended recipient of the email and its attachments please inform the sender immediately and do not disclose the contents to any other person, use it for any purpose or store or copy the information in any way and delete this e-mail and its attachments from your system. Any views or opinions expressed are solely those of the author. ___ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users
[postgis-users] problem to obtain intersection: TopologyException
Hi,
I have a table 'municipio' with a geometric column (the_geom). I want to get a
view with the resultant of the interception between the the_geom column and a
polygon.
The query:
--
SELECT ST_Dump(ST_Intersection(the_geom,
GeomFromText('MULTIPOLYGON(((177056.442675 283157.030268, 283157.030268
192559.320783, 192559.320783 293446.551137, 177056.442675 293446.551137,
177056.442675 283157.030268)))',2085)))
FROM municipio
WHERE the_geom IS NOT NULL
AND ST_Intersects(the_geom, GeomFromText('MULTIPOLYGON(((177056.442675
283157.030268, 283157.030268 192559.320783, 192559.320783 293446.551137,
177056.442675 293446.551137, 177056.442675 283157.030268)))',2085)) = TRUE
return an error:
NOTICE: TopologyException: found non-noded intersection between 178970 311240,
178977 311221 and 178976 311224, 178971 311238 178972 311234
ERROR: GEOS Intersection() threw an error!
** Error **
ERROR: GEOS Intersection() threw an error!
SQL state: XX000
What's the problem
The WHERE statemente ((the_geom, GeomFromText( ...) ) ensure the intersection
Best regards, Salas
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Re: [postgis-users] Geography type
You need PostGIS version 1.5.x and you can read about the geography type here: http://postgis.refractions.net/documentation/manual-1.5/ch04.html#PostGIS_Geography and see supported functions here: http://postgis.refractions.net/documentation/manual-1.5/ch08.html#PostGIS_GeographyFunctions -Mike On 23 September 2010 06:31, Gastón Lucero gaston.luc...@sitrack.com wrote: Sorry for my english. I would like to know the use of the geographic data type. Actually i have to work in represent spherical data. Thanks. Gaston Lucero ___ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users
[postgis-users] Using both and ST_Intersects in a query
Hi, reading the thread Difference between ST_Intersects and operator If I understand exactly this mean that a query filter like this: select ... from table1 as a, table2 as b where ( (a.geom b.geom) (ST_Intersects(a.geom,b.geom)=true ) ) if faster than a query without the like this: select ... from table1 as a, table2 as b where ( ST_Intersects(a.geom,b.geom)=true ) I understand correctly ? Thx, Andrea Peri. ___ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users
Re: [postgis-users] Using both and ST_Intersects in a query
Hi, this mean that a query filter like this: select ... from table1 as a, table2 as b where ( (a.geom b.geom) (ST_Intersects(a.geom,b.geom)=true ) ) if faster than a query without the like this: select ... from table1 as a, table2 as b where ( ST_Intersects(a.geom,b.geom)=true ) This would be true if ST_Intersects would'nt already include a bounding box intersection step before trying the real intersection algorithm. The magic is already in PostGIS :) But you can try the difference with _st_intersects, which only does the geometric intersection without the bbox comparison first. Vincent -- Vincent Picavet - vincent.pica...@oslandia.com www.oslandia.com - Engineering your GIS ___ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users
Re: [postgis-users] Using both and ST_Intersects in a query
This would be true if ST_Intersects would'nt already include a bounding box intersection step before trying the real intersection algorithm. The magic is already in PostGIS :) ok, I'm very glad to know this. Now I need just another little step to complete the question: The bounding-box intersection used in the ST_Intersects is used even when there isn't an index available on geometry field ? Thx for clarification. Andrea. Il 23/09/2010 18:36, Vincent Picavet ha scritto: Hi, this mean that a query filter like this: select ... from table1 as a, table2 as b where ( (a.geom b.geom) (ST_Intersects(a.geom,b.geom)=true ) ) if faster than a query without the like this: select ... from table1 as a, table2 as b where ( ST_Intersects(a.geom,b.geom)=true ) This would be true if ST_Intersects would'nt already include a bounding box intersection step before trying the real intersection algorithm. The magic is already in PostGIS :) But you can try the difference with _st_intersects, which only does the geometric intersection without the bbox comparison first. Vincent ___ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users
[postgis-users] How remove a single part from a multipart geometry
Hi, I need to remove a single part from a multipart geometry. For example having a multipolygon with three part I need to remove one of these parts so the result is a multipolygon with two parts. In postgis I find a function to extract a single part from a multipart ( ST_GeometryN ) but don't find nothing to remove one. So the only method I know is re-create the geometry skipping the part unwanted, but I hope to find somethink more simple. Thx, Andrea. ___ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users
Re: [postgis-users] How remove a single part from a multipart geometry
There aren't any delete/remove/drop geometry functions, so you would need dissect and re-create the geometry. But, if you want to do this visually, this is easy. If you have a recent version of QGIS, just start editing and use the Delete part edit tool. -Mike On 23 September 2010 10:28, Andrea Peri 2007 aperi2...@gmail.com wrote: Hi, I need to remove a single part from a multipart geometry. For example having a multipolygon with three part I need to remove one of these parts so the result is a multipolygon with two parts. In postgis I find a function to extract a single part from a multipart ( ST_GeometryN ) but don't find nothing to remove one. So the only method I know is re-create the geometry skipping the part unwanted, but I hope to find somethink more simple. Thx, Andrea. ___ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users ___ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users
