[Gvsig_english] Question on GeoBD and Metadata when exporting toOracle

Thu Oct 15 10:45:46 CEST 2009

Hello list, (hello Juan Lucas!)
some days ago, I posted some questions on GeoBD and Oracle Spatial to 
this list - and got very good and detailed information.
Today, another question came to me (ok, a colleague asked me that 
question): what type of spatial index is used (if any), if an oracle 
spatial layer is loaded into gvSIG:
or: does gvSIG accept/make use of the R-tree-indexing? My colleague told 
me that Oracle Quadtree indexing was used before and will be replaced by 
R-tree.

Any comment is appreciated.
best,
Wolfgang

---8<----
Wolfgang Qual schrieb:
> Hello Juan Lucas,
> thank you very much for this detailed information. I just found out 
> that SDO_TOLERANCE_1 and .._2 are parameters within the ESRI 
> application. Therefore, they refer to SDO_TOLERANCE values for X and 
> Y. According to my colleague,
> ESRI sets those values to 0.0005.  The tolerance parameter of GeoBD 
> oracle export is set to 0.5 - does that mean that the tolerance is 0.5 
> meter? Can this be modified? As geometries of the common geodatabase 
> are used in different departments with different applications, 
> tolerance values should be identical, don't you think? Sorry, but I am 
> not that well schooled in this oracle stuff...
>
> Best,
> Wolfgang
>
> ---8<---
> And resolution seems to be available in ESRI-software, too.
> Juan Lucas Dominguez Rubio schrieb:
>> Hello, Wolfgang.
>>  
>> When you export a vector layer to Oracle Spatlai/Locator, the 
>> sequence of actions is as follows:
>>  
>> - if a table with the same name exists, it's deleted (dropped in 
>> cascade mode). This also removes spatial indices associated with the 
>> table
>> - the new table is created
>> - geometry metadata for this table name is removed (if existed)
>> - new geometry metadata is written in USER_SDO_GEOM_METADATA
>> - a spatial index on the geometry column is created
>> - table records are added (no commits here)
>> - a single final commit is performed
>>  
>> The tolerance parameter in the metadata is always set to 0.5. 
>> Dimension names are set to 'X', 'Y' and 'Z' (if needed) or 
>> 'LONGITUDE' and 'LATITUDE'. Max. and min. values for X and Y are set 
>> according to the layer's bounding box. Min. and max. values for 'Z' 
>> (if needed) are always set to 0 and 100 (this is not very nice, but 
>> has no bad effect since the Z value does not currently take part in 
>> any geometric operation). Dimension names can be anything you want. 
>> You could use 'BREITE' instead of 'LATITUDE', 'EASTING' instead of 
>> 'X' or whatever.
>>  
>> SDO_TOLERANCE_1 and  SDO_TOLERANCE_2 refer to tolerance for X and Y 
>> perhaps?
>>  
>> Remember that the tolerance unit is implicit and depends on the 
>> table's coordinate system (SRID). If the SRID corresponds to a 
>> geodetic coordinate system (latitude, longitude), then the tolerance 
>> is assumed to be expressed in meters. If the SRID corresponds to a 
>> projected coordinate system (such as the German EPSG:3146X series) 
>> then the tolerance is assumed to be expressed in the same unit used 
>> by the coordinate system (usually meters). This also applies if the 
>> SRID is NULL. According to this, it would be a bad idea to have a 
>> table with geometries whose vertices are in latitude and longitude 
>> and setting the SRID to NULL, because the tolerance (0.5) would 
>> correspond to a few dozens of kilometers.
>>  
>> The tolerance settings are very unlikely to have any effect when you 
>> work with gvSIG because the application checks again the true 
>> relationship between geometries after they have been converted to the 
>> gvSIG geometry model. In other words: the 'select by rectangle' tool 
>> should not behave in a strange way even if you have a bad tolerance 
>> value. Of course you will see the effects of a bad tolerance value 
>> from other applications or when you execute a SQL statement directly 
>> against your database.
>>  
>> So the metadata stored for a Oracle Spatial/Locator table are:
>>  
>> - Owner
>> - Table name
>> - Geometry column name (the metadata record will be replicated for 
>> several values because a table can have more than one geometry column)
>> - Dimension info (for each dimension: dimension name, max value, min 
>> value, tolerance)
>> - SRID (possibly NULL)
>>  
>> If you have a 3D vector layer (for example a 3D shapefile) I think 
>> you will not notice the third dimension while you work with views and 
>> layouts, but if you export that layer to your Oracle Spatial/Locator 
>> database, it will be stored with a 3D geometry column (you can see 
>> the number of dimensions of each using Sqldeveloper for example)
>>  
>> As you perhaps know, Oracle Spatial/Locator supports 4D geometries 
>> (XYZT, I think Oracle normally uses the letter T instead of M for the 
>> 4th dimension). When you open one of these tables with gvSIG, the 
>> resulting layer is a 3D layer (4th dimension is discarded)
>>  
>> I have never heard about a parameter called resolution in the table 
>> metadata. Perhaps you are talking about some operations that allow 
>> you to restrict the result by setting a min and max_resolution value, 
>> but this is not connected to tables' metadata.
>>  
>> I agree that it would be a good idea to let the user set the metadata 
>> values.
>>  
>> Regards,
>> Juan Lucas Domínguez Rubio
>> ---
>> Prodevelop SL, Valencia (España)
>> Tlf.: 96.351.06.12 -- Fax: 96.351.09.68
>> http://www.prodevelop.es <http://www.prodevelop.es/>
>> ---
>>
>> ------------------------------------------------------------------------
>> *De:* gvsig_internacional-bounces at listserv.gva.es en nombre de 
>> Wolfgang Qual
>> *Enviado el:* jue 24/09/2009 8:59
>> *Para:* Users and Developers mailing list
>> *Asunto:* [Gvsig_english] Question on GeoBD and Metadata when 
>> exporting toOracle
>>
>> Hi list,
>> in our City administration, different GIS software is used to work with
>> spatial data. Among them, ArcMap and gvSIG allow to access a central
>> oracle spatial database. Thanks to the great GeoBD extension, accessing
>> that database via gvSIG is very comfortable, even exporting new layers
>> to the database is possible.
>> Yesterday, a colleague of mine who is in charge of the overall design of
>> the geodatabase asked me to provide some details on GeoBD's
>> capabilities. He asked me about metadata that is created by that
>> extension when exporting a shapefile to the oracle spatial database and
>> possibilities to set custom settings for the metadata. In this context,
>> he also talked about "tolerance" (SDO_TOLERANCE_1, SDO_TOLERANCE_2),
>> "resolution". I have no idea, whether GeoBD sets these values.
>> Therefore, I would be very happy, if someone of you (maybe the
>> developers from Prodevelop) could give me some details on the type and
>> values of metadata that is written to new oracle spatial layers. That
>> would be very great to have.
>>
>> Best regards and thank you very much for your help.
>> Wolfgang
>>
>> --
>> Wolfgang Qual
>> Landeshauptstadt München
>> Referat für Gesundheit und Umwelt
>> RGU-UW 11
>> Sg. 1 Gesundheits- und Umweltberichterstattung,
>> Energie und Klimaschutz
>> Bayerstr. 28a, 80335 München
>> Tel.: +49 (0)89 233-477 17
>> Fax.: +49 (0)89 233-477 05
>> E-Mail: wolfgang.qual at muenchen.de
>>
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>
>
> -- 
> Wolfgang Qual
> Landeshauptstadt München
> Referat für Gesundheit und Umwelt
> RGU-UW 11
> Sg. 1 Gesundheits- und Umweltberichterstattung, 
> Energie und Klimaschutz 
> Bayerstr. 28a, 80335 München
> Tel.: +49 (0)89 233-477 17
> Fax.: +49 (0)89 233-477 05
> E-Mail: wolfgang.qual at muenchen.de 

-- 

	*Wolfgang Qual

* *Referat für Gesundheit und Umwelt*
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