[postgis-users] srid

[Paragon Corporation]

Bob,
You are  wrong about that.  ST_Translate is always in whatever your spatial
ref is.  So if your spatial reference is undefined then the float is in
whatever you think you are measuring

So if you have a point (90,20)

ST_Translate(yourpoint,1,2)  -> point(91,22)

Below example might help

http://www.bostongis.com/postgis_translate.snippet

Hope that helps,
Regina

-----Original Message-----
From: postgis-users-bounces at postgis.refractions.net
[mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of Bob
Pawley
Sent: Tuesday, May 27, 2008 12:06 AM
To: PostGIS Users Discussion
Subject: Re: [postgis-users] srid

I considered ST_Translate but the float 8 seems to require an offset in feet
or meters.

Perhaps I am wrong about that?

Bob
----- Original Message -----
From: "Andy Anderson" <aanderson at amherst.edu>
To: "PostGIS Users Discussion" <postgis-users at postgis.refractions.net>
Sent: Monday, May 26, 2008 7:46 PM
Subject: Re: [postgis-users] srid


It seems like you might be better off using ST_Translate() to
translate an object's location than to use ST_Transform() to change
the underlying spatial reference. If you want to draw objects on the
same canvas, you need to have them in the same spatial reference;
that's the purpose of ST_Transform(). If you can start with everything
in the same spatial reference and merely translate them around, I
would think it would involve a lot less processing.

-- Andy

On May 26, 2008, at 9:33 PM, Bob Pawley wrote:

> 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
>>> _______________________________________________
>>> 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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