[postgis-users] srid

[Chris Hermansen]

I guess if you had, say, a two level structure to your data:

1. process A
1.1 sub-process A-i)
1.2 sub-process A-ii)
2. process B
2.1 sub-process B-i)
2.2 sub-process B-ii)
2.3 sub-process B-iii)

for example, then this "conceptually" places one box beside another
without knowing the actual coordinates.

from that you could compute coordinates, that gets into the stored
procedure stuff I was talking about below, or you could write in say Python.

at the bottom, though, if you want to "place the boxes in space" you
pretty much have to give them coordinates somehow.

the operators like ">>" don't do this for you.  they tell you whether
something is beside something else, or on top of, or whatever - actually
the operators tell you about the bounding boxes, not the objects themselves.

they don't "put things somewhere", because that's assigning coordinates.

if you want to "put something somewhere", at some level, you need to see
statements like

update foo set the_geom = GeomFromText('POINT(0 0)',-1) where level1 = 1
and level2 = 0;
update foo set the_geom = GeomFromText('POINT(0 10)',-1) where level1 =
1 and level2 = 1;
update foo set the_geom = GeomFromText('POINT(0 20)',-1) where level1 =
1 and level2 = 2;
update foo set the_geom = GeomFromText('POINT(10 0)',-1) where level1 =
2 and level2 = 0;

etc

Bob Pawley wrote:
> Hi Chris
>
> I want to explore your thought of using 'boxes' as targets.
>
> Is there some method of placing one box beside another without knowing
> the actual coordinates.
>
> I've seen the operators (>>) but I can't find how to do anything with
> them other than querying their position.
>
> Bob
>
>
> ----- Original Message ----- From: "Chris Hermansen"
> <chris.hermansen at timberline.ca>
> To: "PostGIS Users Discussion" <postgis-users at postgis.refractions.net>
> Sent: Monday, May 26, 2008 6:05 PM
> Subject: Re: [postgis-users] srid
>
>
>> Or, in another direction... Bob, if your "geometrical data" is meant to
>> be something like a "data flow diagram" or a "process diagram", you can
>> surely do that with PostGIS.
>>
>> Doubtless you must be aware of tools like Visio (in Windoze) or Dia (in
>> Linux or Windoze) that are made for drawing diagrams like "data flow",
>> but nevertheless you've decided to put your data into PostGIS instead.
>>
>> Then you probably want to make some "boxes" in your process diagram
>> appear above, below, to the right of, or to the left of, other boxes.
>>
>> To do that, you would need to define some kind of partial order on the
>> boxes (this box is to the right of that box, etc).  This sounds like a
>> topological sort to me.
>>
>> Presumably you could turn that topological ordering into some set of
>> offsets that could be applied to compute coordinates of each box.
>>
>> is that where you're trying to end up?
>>
>> Andy Anderson wrote:
>>> On May 26, 2008, at 3:06 PM, Bob Pawley wrote:
>>>
>>>> However, I attempting to interpret functions made for geographic data
>>>> to use with geometric data.
>>>>
>>>> I have PostgreSQL tables which represent engineering processes.
>>>>
>>>> I want to display that data in a graphical form - hopefully using
>>>> Postgis - - - if I can translate the functions (or the Postgis
>>>> concept) into a form that I can use.
>>>
>>> Hmmm... if all you want to do is display X-Y data, I would suggest
>>> using geographic coordinates, e.g. SRID = 4326 (WGS84 datum), which
>>> most programs will display by default with X and Y rectilinear.
>>>
>>> However, you earlier said you wanted to use ST_Transform(geometry,
>>> integer), which implies you want to switch between different
>>> geographies.
>>>
>>> So it sounds like you need to pick a particular projection for your
>>> work.
>>>
>>> Is your geography spherical or spheroidal? If so, you might want to
>>> define your own datum. If not, you'll need to use a projection to a
>>> flat surface. What's more important, that it be conformal
>>> (equiangular) or equal area or that it preserve distance in one
>>> direction?
>>>
>>> -- Andy
>>> _______________________________________________
>>> postgis-users mailing list
>>> postgis-users at postgis.refractions.net
>>> http://postgis.refractions.net/mailman/listinfo/postgis-users
>>
>>
>> -- 
>> Regards,
>>
>> Chris Hermansen         mailto:chris.hermansen at timberline.ca
>> tel+1.604.714.2878 · fax+1.604.733.0631 · mob+1.778.232.0644
>> Timberline Natural Resource Group · http://www.timberline.ca
>> 401 · 958 West 8th Avenue  · Vancouver BC · Canada · V5Z 1E5
>>
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>
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-- 
Regards,

Chris Hermansen         mailto:chris.hermansen at timberline.ca
tel+1.604.714.2878 · fax+1.604.733.0631 · mob+1.778.232.0644
Timberline Natural Resource Group · http://www.timberline.ca
401 · 958 West 8th Avenue  · Vancouver BC · Canada · V5Z 1E5