[postgis-users] srid

[Chris Hermansen]

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
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