[postgis-users] Postgresql, postgis and PHP

Thu Feb 3 07:46:47 PST 2011

Hi,

Thank you very much for the info. Will check this out.
I got some info and examples on the site: 
http://trac.osgeo.org/postgis/wiki/UsersWikiMain and that already helped 
me quite a bit. It's going slow but at the moment there are already some 
nice stuff I accomplished.

I will read through the links you sent me, and come back to you guys for 
questions.

Regards,
LJ du Toit

__________________________________________________
LJ du Toit

On 03.02.2011 16:36, Paragon Corporation wrote:
> LJ,
>
> The first chapter is a free download.  We took Paolo Coriti's advice (hmm I
> think others suggested it to),and made the first chapter very quick paced.
> So it covers, geometry, geography types, how to load and how to do common
> spatial joins with it.
>
> You might want to check that out.
>
> It's changed quite a bit from the one that is currently posted on the site,
> but I think most of the pieces are there.
>
> http://www.manning.com/obe/PostGIS_MEAPCH01.pdf
>
> Also all the code snippets and most of the data for the chapters are
> available on our book site  and we don't require you to buy the book to
> download them.  Though it helps since the book is more descriptive of what
> is going on in the code. Just click on the paper clip to download the code
> and accompanying data  for each chapter (the link is also available on each
> chapter description page)
>
> http://www.postgis.us/chapters
>
>
> There are also some good examples and walk thru tutorials on the PostGIS
> users site
>
> http://trac.osgeo.org/postgis/wiki/UsersWikiTutorials
>
>
>
>
>
> Hope that helps,
> Leo and Regina
> http://www.postgis.us
>
>
>
> -----Original Message-----
> From: postgis-users-bounces at postgis.refractions.net
> [mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of Louwrens
> du Toit
> Sent: Thursday, February 03, 2011 5:38 AM
> To: PostGIS Users Discussion
> Subject: Re: [postgis-users] Postgresql, postgis and PHP
>
> Hi Brent,
>
> First of all thanks for the reply and the heads up warning for
> conversions... I will look into that book that you mentioned but would like
> to know (like Dheeraj) if you could perhaps give me a hint on how such a
> query could look? That would very much be appreciated.
>
> Thanks again for the info.
>
> Regards,
> LJ du Toit
>
> __________________________________________________
> LJ du Toit
>
> Max-Planck-Institute for Evolutionary Anthropology Department of Primatology
> Deutscher Platz No 6
> D-04103 Leipzig
> Germany
>
> e-mail    louwrence_du at eva.mpg.de
> phone    ++49 (0) 341 3550 802
>
>
> On 02.02.2011 19:44, Dheeraj Chand wrote:
>> Brent,
>>
>> I confess to being in a similar boat to the OP. I just pre-ordered the
> book from Amazon, but I am curious if you can get into your opinions about
> whether or not it's better to do that kind of manipulation at the db level
> or at the script level.  My gut tells me that it's better to do it by db.
>> More interestingly, what would a query to accomplish his goals look like?
>>
>> Dheeraj
>>
>> On Feb 2, 2011, at 1:25 PM, pcreso at pcreso.com wrote:
>>
>>> Hi,
>>>
>>> You can use simple SQL to extract core values which you manipulate&
> analyse in PHP/Javascript, or you can do more of the work in SQL. Given your
> skills, it seems likely that you would find it easier to use simple SQL&
> more script based processing.
>>> One initial point to note:
>>>
>>> If you are dealing with global polygons, then SRID 4326 based data can
> give very strange results for area calculations. eg, the polygons:
>>> (0 0,  1 0,  1 1,  0 1,  0 1 ) and
>>> (0 90, 1 90, 1 89, 0 89, 0 90)
>>>
>>> are both 1 degree square, and will give you the same area when queried.
> However, these are cartesian degrees, and you want the spherical area, which
> will be close to 1 degree at the equator, but a small fraction of this at
> the pole.
>>> So, you need to either convert (transform) your coordinates to a suitable
> coordinate system (identified by its SRID) before querying the area, or deal
> with this issue some other way, but you need to deal with it.
>>> Then you can use the Postgis SQL functions to retrieve the desired area
> values of the transformed polygon geometries. The Postgis docs give you good
> basic instructions on the commands, but tend to assume you already
> understand such issues.
>>>
>>> Rather than write a Postgis guide here, I recommend you buy a copy of
> "Postgis is Action" (http://www.manning.com/obe/) - you can download the
> digital version prior to the printed edition being available.
>>> Otherwise a full discussion on this list could virtually replicate the
> contents of the book!
>>>
>>> Cheers,
>>>
>>>    Brent Wood
>>>
>>>
>>> --- On Wed, 2/2/11, Louwrens du Toit<louwrence_du at eva.mpg.de>   wrote:
>>>
>>>> From: Louwrens du Toit<louwrence_du at eva.mpg.de>
>>>> Subject: [postgis-users] Postgresql, postgis and PHP
>>>> To: postgis-users at postgis.refractions.net
>>>> Date: Wednesday, February 2, 2011, 11:24 PM Dear Postgis-Users List,
>>>>
>>>> I'm an experienced web developer (mainly PHP, Javascript,
>>>> MySQL) and have recently started a job where I need work with
>>>> geographic information, mainly in a Postgresql database. So, I'm
>>>> quite new to all this geographical data etc and have a few
>>>> questions:
>>>>
>>>> So, I have a database (Postgresql) with geographical data (mainly
>>>> polygons in format "geometry" - srid 4326). Now I can do some area
>>>> (ST_Area) and intersection
>>>> (ST_Intersection) queries but would like to know the
>>>> following:
>>>>
>>>> 1. I have several tables with polygon data (layers) but need to do
>>>> queries across them (what I need to do in the end is to create
>>>> charts - bar,pie etc). I.e I would like to know for instance, what
>>>> percentage area of layer 1 falls within the area in layer 2? or 2. I
>>>> have raster data (in geotiff format), and would like to know... per
>>>> polygon (in layer 1 above), what is the mean value of the raster
>>>> data...
>>>>
>>>> Can someone point me in a direction of where to information like
>>>> this. How should I go about this problem?
>>>>
>>>> I hope this makes sense. As I said, I'm very new to all this
>>>> geographic stuff.
>>>>
>>>> Thank you,
>>>> LJ du Toit
>>>>
>>>> --
>>>> __________________________________________________
>>>> LJ du Toit
>>>>
>>>> _______________________________________________
>>>> postgis-users mailing list
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>>>>
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