get_antelope_traces fails when data files are missing

[gthompson]

From @GoogleCodeExporter on August 1, 2015 21:51

What steps will reproduce the problem?
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   scnl=scnlobject('SIT','BHZ','','');
   ds = datasource('uaf_continuous');
   startTime = '06-Jan-2000 10:41:42';
   endTime = '06-Jan-2000 10:43:42';
   w = waveform(ds,scnl,startTime,endTime);


What is the expected output? What do you see instead?
-----------------------------------------------------------
The above example errors out in an unintelligible way. I believe this is 
because database entries actual exists for this scnl and time. However the 
waveform files themselves have been taken offline. This failure should happen 
frequently for waveform calls prior to October 2002. It is conceivable that it 
would happen on rare occasions at other times. It is a problem that could occur 
when calling any malformed .wfdisc table. (Ultimately this is the result of 
poor database integrity. The fact is, though, it happens.)

I suspect the fix is a simple additional check in 
load_antelope>get_antelope_traces. There is surely a formal database way to do 
this check. I don't know it however. The question is how to ask the database 
whether or not data claimed in a wfidisc row, actually exists on file?

Any thoughts on this last question would be welcomed.

Original issue reported on code.google.com by mew...@alaska.edu on 8 Nov 2011 at 9:41

Copied from original issue: giseislab/gismotools#28

[gthompson]

This test could be implemented by calling https://github.com/geoscience-community-codes/GISMO/blob/master/classes/%2Bantelope/listMiniseedFiles.m

It takes the same arguments as waveform. So I sometimes call it before waveform, e.g.

flist = listMiniseedFiles(ds, scnl, snum, enum)
if sum(flist.exists)>0
    w = waveform(ds, scnl, snum, enum)
end