[IDV #MQM-696970]: visad error propagation facility

Hi Tyn-

> A bit of hack, but would this be a possibility to support pixel-specific 
> errors?
> 
> 
> 
> sampleToReal(FieldImpl grid, FieldImpl grid error-estimate, LatLonPoint 
> point, int samplingMode, int errorMode)

I'm not sure what you would want this to do.  If you just want the error 
estimate at the point and you have an error/pixel in the error-estimate grid, 
you could do something like:

a = sampleToReal(grid, point, samplingMode, errorMode)
b = sampleToReal(grid_error_estimate, point, samplingMode, errorMode)
realWithError = Real(a.getType(),a.getValue(), a.getUnit(), b.getValue())

Will that work?

Don

> 
> This since I need something on the short term. We are still exploring the 
> long-term solution (FieldImpl with Reals)...
> 
> 
> 
> Tyn
> 
> 
> 
> -----Original Message-----
> From: Unidata IDV Support [mailto:address@hidden]
> Sent: Tuesday, February 23, 2010 5:24 PM
> To: Valentijn Venus
> Cc: address@hidden
> Subject: [IDV #MQM-696970]: visad error propagation facility
> 
> 
> 
> Hi Tyn-
> 
> 
> 
> > Further to my previous message, I already found some answers to some of my 
> > questions. However, can you comment on the ??? below.
> 
> >
> 
> > > What are the numerical equivalents for the other propagations methods to 
> > > set int errorMode correctly?
> 
> >
> 
> > Data.NO_ERROR    = 202
> 
> > Data.INDEPENDENT = ???
> 
> > Data.DEPENDENT   = ???
> 
> 
> 
> Data.INDEPENDENT = 200
> 
> Data.DEPENDENT   = 201
> 
> 
> 
> I've added the following to GridUtil so you can use them there:
> 
> 
> 
> public static final int NO_ERRORS = Data.NO_ERRORS;
> 
> public static final int DEPENDENT_ERRORS = Data.DEPENDENT;
> 
> public static final int INDEPENDENT_ERRORS = Data.INDEPENDENT;
> 
> 
> 
> I've also added an error mode to the sampleToReal. sample already had the 
> error mode signature.
> 
> 
> 
> These will be in tomorrow's build.
> 
> 
> 
> > http://www.unidata.ucar.edu/software/idv/docs/javadoc/constant-values.html#ucar.unidata.data.grid.GridUtil.DEFAULT_ERROR_MODE
> 
> >
> 
> > > Is there a javadoc showing all propagations methods?
> 
> >
> 
> > NO, except this snippet in 
> > http://www.unidata.ucar.edu/mailing_lists/archives/visad/2002/msg00170.html:
> 
> >
> 
> >
> 
> > > Also, I can see that Data.INDEPENDENT uses a linear 'error
> 
> > > propagation' algorithm, but what does actually Data.DEPENDENT do (doesn't
> 
> > > one need to know the functional form of the dependency?). Is there any
> 
> > > auxiliary documentation somewhere, or references to the algorithms used?
> 
> >
> 
> > For Data.DEPENDENT the system uses the worst case error
> 
> > propagation, where they are simply added. This is essentially
> 
> > interval arithmetic. For Data.INDEPENDENT the system uses
> 
> > root mean square error propagation.
> 
> 
> 
> I don't know any more than what was in that message.  As Bill pointed out, 
> this has not been tested very well. I have no experience using the error 
> propagation, but if you run into problems, we can muddle along together. ;-)
> 
> 
> 
> Don
> 
> 
> 
> > -----Original Message-----
> 
> > From: Unidata IDV Support [mailto:address@hidden]
> 
> > Sent: Wednesday, May 13, 2009 12:25 AM
> 
> > To: Valentijn Venus
> 
> > Cc: address@hidden
> 
> > Subject: [IDV #MQM-696970]: visad error propagation facility
> 
> >
> 
> > Hi Tyn-
> 
> >
> 
> > > thanks!
> 
> > >
> 
> > > Unfortunately, not everything is done with visad.
> 
> >
> 
> > It will be difficult to do the error propagation fully then.
> 
> >
> 
> > > On the IDV side, would it take a lot of work to for all methods to pass 
> > > an error propagation type other than Data.NO_ERROR? Do you think Willem 
> > > could handle such a task?
> 
> >
> 
> > You'd need a way for the user to set the error mode and then modify all the
> 
> > methods in GridUtil that take a sampling method to also take an error mode.
> 
> > I took a stab at the latter, but not sure I got all the methods yet.  Then
> 
> > any of the controls/methods that do sampling would need to implement this
> 
> > as well.
> 
> >
> 
> > I'm sure there are other gotcha's out there.  We're in the middle of
> 
> > finalizing the 2.7 release, so don't have time to work on this.  If
> 
> > Willem wants to look into it I can try to answer some of his questions.
> 
> >
> 
> > Don
> 
> >
> 
> >
> 
> > Ticket Details
> 
> > ===================
> 
> > Ticket ID: MQM-696970
> 
> > Department: Support IDV
> 
> > Priority: Normal
> 
> > Status: Open
> 
> >
> 
> >
> 
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> 
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> 
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> > 9:02 AM
> 
> > Faculty of Geo-Information Science and Earth Observation (ITC)
> 
> > University of Twente
> 
> >
> 
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> 
> 
> Ticket Details
> 
> ===================
> 
> Ticket ID: MQM-696970
> 
> Department: Support IDV
> 
> Priority: Normal
> 
> Status: Open
> 
> 
> 
> Faculty of Geo-Information Science and Earth Observation (ITC)
> University of Twente
> 
> E-mail disclaimer
> The information in this e-mail, including any attachments, is intended for 
> the addressee only. If you are not the intended recipient, you are hereby 
> notified that any disclosure, copying, distribution or action in relation to 
> the content of this information is strictly prohibited. If you have received 
> this e-mail by mistake, please delete the message and any attachment and 
> inform the sender by return e-mail. ITC accepts no liability for any error or 
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Ticket Details
===================
Ticket ID: MQM-696970
Department: Support IDV
Priority: High
Status: Open