This thread seems to ignore the fact that web2py_postgresql support GIS:
http://web2py.com/books/default/chapter/29/06/the-database-abstraction-layer?search=st_distance
Given:
from gluon.dal import geoPoint
db.define_table('point', Field('name'), Field('loc','geometry()'))
query = db.point.loc.st_distance(geoPoint(-1,2))<10
rows = db(query).select(db.point.name)
On Friday, 29 November 2013 10:46:34 UTC-6, Ruud Schroen wrote:
>
> I found a Python version of the link you posted:
>
> >>> loc = GeoLocation.from_degrees(51.441642, 5.469722)
> >>> distance = 1000 # 1 kilometer
> >>> SW_loc, NE_loc = loc.bounding_locations(distance)
> >>> print SW_loc
> >>> print NE_loc
> >>> print loc.distance_to(SW_loc)
> >>> print loc.distance_to(NE_loc)
>
> This function should create a box.
> Now this is the output in my terminal:
>
> (42.4584deg, -9.0379deg) = (0.741040rad, -0.157741rad)
> (60.4248deg, 19.9773deg) = (1.054613rad, 0.348670rad)
> 1483.52131402
> 1342.64671093
>
>
> Also, I saw this post.
>
> My guess is that I should do the following:
>> Get the logged in users geo information (lat and long)
>> Get the distance away that I want to search around that person and
>> calculate the lat and logitudes of that area...
>> Find if the lat and log of the items.lat and items.long in my database
>> are within the regions of the users.lat and users.log and the (areas.lat
>> and areas.long)* for for four directions.
>>
>
> What values do i need to use in my query?
>
>
> On Fri, Nov 29, 2013 at 3:26 PM, Oscar Fonts <[email protected]<javascript:>
> > wrote:
>
>> Hi Ruud,
>>
>>
>> > when I fetch the records, i only want those records which have a
>> distance *equal to or below the given distance*.
>>
>> The usual technique in the geospatial world is to first select the points
>> from the containing rectangle (bounding box, or BBOX), which is a much
>> simpler calculation that helps discard most of the unwanted points. Then
>> calculate the distance against the points inside that BBOX. Something like:
>>
>> SELECT * FROM table
>> WHERE
>> LAT >= :min_lat
>> AND LAT <= :max_lat
>> AND LON >= :min_lon
>> AND LON <= :max_lon
>> HAVING (distance_calculation) <= :radius
>>
>> The HAVING condition is only checked against the rows satisfying the
>> WHERE conditions, so it's a good way to refine your selection with an
>> expensive calculation.
>>
>> Obviously you'll want to index LAT and LON fields as well.
>>
>> Details on formulae for bbox and distance calculations:
>> http://janmatuschek.de/LatitudeLongitudeBoundingCoordinates
>>
>>
>> --
>> Oscar Fonts
>> www.geomati.co <http://geomati.co>
>>
>> --
>> Resources:
>> - http://web2py.com
>> - http://web2py.com/book (Documentation)
>> - http://github.com/web2py/web2py (Source code)
>> - https://code.google.com/p/web2py/issues/list (Report Issues)
>> ---
>> You received this message because you are subscribed to a topic in the
>> Google Groups "web2py-users" group.
>> To unsubscribe from this topic, visit
>> https://groups.google.com/d/topic/web2py/ahO2ydF7yK0/unsubscribe.
>> To unsubscribe from this group and all its topics, send an email to
>> [email protected] <javascript:>.
>> For more options, visit https://groups.google.com/groups/opt_out.
>>
>
>
--
Resources:
- http://web2py.com
- http://web2py.com/book (Documentation)
- http://github.com/web2py/web2py (Source code)
- https://code.google.com/p/web2py/issues/list (Report Issues)
---
You received this message because you are subscribed to the Google Groups
"web2py-users" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
For more options, visit https://groups.google.com/groups/opt_out.
