Re: Oracle Spatial Attributes

From: Hans Forbrich <hforbric_at_yahoo.net>
Date: Thu, 19 Feb 2004 20:08:34 GMT
Message-ID: <6J8Zb.26134$n17.21075@clgrps13>

FinnE wrote:

> Hans Forbrich <hforbric_at_yahoo.net> wrote in message news:<s84Zb.30295$D_5.9646_at_edtnps84>...
> 

>>FinnE wrote:
>>
>>>Is it possible to have multiple spatial attributes in a single
>>>database record in Oracle9i or higher?
>>
>>Yes.
>>
>>Some orgs use this fact to have high/med/low resolution point
>>information in a table allowing the front-end app to switch and chose
>>the appropriate amount of data to transfer.
>>
>><elabortion>
>>What you refer to as 'Spatial attributes' are object types. You can
>>have any number in a table and each 'appears' as a column.
>>
>>Quick def of the spatial object: There are 5 fields
>>- general type of data indicator,
>>- coord-system_id (if using projected coord system),
>>- single point coords (if type indicates it's only a point),
>>- a list for the 2D/3D/(+added info such as LRS) data points (generally
>>counter-clockwise),
>>- a list that indicates at which point gives a new data definition
>>(polygon starts here, curve starts here, etc.)
>>
>><more info source>
>>There are a number of excellent tutorials in Oracle's OnLine library at
>>http://Education.oracle.com
>></more info source>
>></elabortion>
>>
>>HTH
>>/Hans
>>
>>(BTW - no need to cross-post)

> 
> 
> Where in the oracle documentation does it give you that information? 
> Also do you know - to what precision can Oracle Spatical store arcsec?
> Erin

In the Spatial documentation. To get to the docco ...

http://docs.oracle.com

 >> the database version you're working on
 >> 'View Library' link
 >> 'List of Books' link
 >> Spatial User's Guide and Reference (about 60% down the page)

The precision depends on the projection, if used, and the version of database. However, in general you don't use precision, instead you specify the tolerance. (Aside from the 950+ known projections, you can also define your own coord system as well, and override tolerance for that.)

As of 9iR2, if using geodetics, your tolerance is specified in meters and is generally set at .005 meters. (Converting between defined projections and geodetics is accomplished using viewport transformations, so you can likely get the data to the arc spec you need).

HTH
/Hans Received on Thu Feb 19 2004 - 14:08:34 CST