[postgis-users] srid

[Bob Pawley]

That is what I am attempting.

I know of Visio. My thought of using Postgis is to, if possible, use the 
functions that Postgis provides. In the very long range I was also 
considering the 3D aspect of Postgis.

Your suggestion of using "boxes", presumably to provide reference points is 
my backup method, if ST_Transform isn't applicable.

I would still like to consider ST_Transform as it appears to be a more 
flexible approach.

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
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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
>
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