Doubts in GeoRaster Concept.
Hi everybody,
I have few doubts in GeoRaster concepts.
I did mosaicing of multiple Georasater objects using "sdo_geor.getRasterSubset()" and able to display image properly. But while doing this I come across few people suggestions. They said that mosaicing multiple rows together in a GeoRaster table is not going produce meaningful results because the interpolation methods wont have access to the data in the adjacent cells at the seams because cell needed exist in a different row (i.e. where two rows of GeoRaster either abut or overlap).
I assume Oracle takes care of all this. Please suggest wheather my assumption is true or the statement given is true?
Regards,
Baskar
Edited by: user_baski on May 16, 2010 10:49 PM
Hi Jeffrey,
Requirements:-
I have to do mosaicing of 'n' number of Georaster objects. For eg, if table has 4 rows of GeoRaster object, then i have to create single image by mosaicing all the Georaster object based on the Envelope provided. (Note: I have to do this with Queries without using GeoRaster API)
Workflow:-
1. Get the connection and table details.
2. Retrieve necessary information from the db like SRID, MAXPYRAMID, SPATIALRESOLUTION, EXTENT etc. For getting extent, I used SDO_AGGR_MBR function.
3. With the help of "MDSYS.SDO_FILTER" and bouding box values, I create arraylist which contains raster id's retrieved from raster data table which covers the bouding box value provided in the filter command.
4. Then I passed bounding box value into "sdo_geor.getCellCoordinate" function and I retrieved row and column number of Georaster image and created a number array which contains starting and ending row/column numbers.
5. Then I had written a PL/SQL with "sdo_geor.getRasterSubset" function which takes the number array and raster id as input parameters, which inturn returns BLOB object.
6. I am executing step 5 in a loop with all the raster id's that I got at step 3. For eg, arraylist size is 4, then I will have four BLOB object.
7. Finally, I creating new image from the BLOB objects after some scaling and cropping based on the individual GeneralEnvelope of each raster id object.
I had followed all the above steps and successfully created mosaic image.However, few people suggested that mosaicing in this way does not produce meaningful results because the interpolation methods wont have access to the data in the adjacent cells at the seams because cell needed exist in a different row. I assume Oracle will take care of these things. Moreover, they suggested to keep single row in GeoRaster table instead of muliple rows of Georaster object and suggested to use "SDO_GEOR.updateRaster" function to update a part of the raster object and the pyramids are rebuild automatically.
So Please suggest which is the better way to do mosaicing. Wheather my assumption is correct or not?
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3
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15
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HTH
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Message was edited by:
David Tyler
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endasil wrote:
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Say we have a class called Animal which has a method called shout().
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Hi Experts,
I've got few doubts understanding the concepts of Locking.
I'm referring this article - http://docs.oracle.com/cd/E14072_01/server.112/e10592/ap_locks001.htm
1]
>
When a transaction obtains a row lock for a row, the transaction also acquires a table lock for the table in which the row resides.
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What is the significance of the 2 ^nd^ line? Does that mean, at that time we can't DROP or ALTER the table structure ??
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A row share lock (RS), also called a subshare table lock (SS), indicates that the transaction holding the lock on the table has locked some rows in the table and intends to update them, as is the case in a SELECT ... FOR UPDATE statement. An SS lock is the least restrictive mode of table lock, offering the highest degree of concurrency for a table.
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- What is the need of an SX lock when it allows other transactions to manipulate data?
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3]
>
A share table lock (S) held by one transaction allows other transactions to query the table but allows updates only if a share table lock is held by only a single transaction. Multiple transactions may hold a share table lock concurrently, so holding this lock is not sufficient to ensure that a transaction can modify the table.
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>
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Edited by: ranit B on Nov 28, 2012 6:47 PM
-- added [3]padders wrote:
Does that mean, at that time we can't DROP or ALTER the table structure Yes, that's pretty much what it means.
What is the need of an SX lock when it allows other transactions to manipulate data?As the text says - the lock allows concurrent update of other rows - i.e. you lock some row(s) but other rows can still be updated.Thanks Padders.
But then, what is the difference between SS and SX? Both allow other rows to be updated.
Please rectify me if I'm wrong.
I got some idea. It would be really helpful if you could please give me some pointers on the other doubts also? -
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class FileDemo
public static void main(String[] args)throws IOException
String st = "123456789";
int c;
byte[] buf = st.getBytes();
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for(int i=0;i<8;++i)
c = f.read();
System.out.print((char)c);
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c = f.read();
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12345678
9In above code when i execute f.mark(5), the file pointer should make a mark at 5th byte i.e character 5, and when i execute reset the file pointer must point back to this 5th byte and must print 5 when i print for the next time. But instead the output i get is 9 after reset is executed. Please clarify.....In above code when i execute f.mark(5), the file
pointer should make a mark at 5th byte i.e character 5No, it shouldn't.
and when i execute reset the file pointer must
point back to this 5th byte and must print 5 when i
print for the next time. But instead the output i get
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How to renormalize number of flows in Netflow Sampled data
Hi,
I am working on extrapolation(renormalization) of bytes/packets/flows from randomly sampled (1 out of N packets) collected data. I believe bytes/packets can be renormalized by multiplying bytes/packets value in exported flow record by N.
Now, I am trying to extrapolate number of flows. So far i have not got any information on it. Do you people have any idea on how flows can be renormalized from sampled data ?
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1. In packet sampling, we do not know how many flows got dropped. Even router cache will not have entries for dropped flows
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DeepakThe simplest way is to call GetTableCellRangeValues with VAL_ENTIRE_TABLE as the range, next summing array elements.
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