Re: [thredds] Scan Aggregation vs. Feature Collection

Well, its complicated.

Old style aggregations, aka "NcML aggegations" remain supported. I think of these as low level index manipulations. These are embedded in NcML, either on the client or in TDS config catalog, see:

We can do much better when we know the "feature type", and the new way is called "feature collections":

1) type=FMRC is for gridded data. Works mostly of in 4.2, but refactored in 4.2 and still testing. 2) type=GRIB is for GRIB data, which is a special kind of gridded data. This supersedes FMRC when the data is in GRIB. Only in 4.3, ready for beta test.
3) type=point are for point feature types. Still in alpha in 4.3

NcML works fins when you know what you are doing and you have homogenous files. feature collections are intededd to be easier to use and tolerate heterogeneous files.


On 7/23/2012 3:27 PM, Roy Mendelssohn wrote:
But is this just for FMRC aggregation, or for all aggregations?  I could swear I remember a web age with 
feature collections that "grid" was a feature type, but when I looked the other day, it was point, 
station and grib I believe.  Maybe it was my old age and bad vision seeing "grid" for 
"grib".  If there is an aggregation for featureType=grid, can you point me to the page that 
describes this.

We do not have any FMRC aggregations, but if there all of our aggregations 
should be feature collections, then I have a lot of editing to do on our xml 



On Jul 23, 2012, at 1:59 PM, John Caron wrote:

On 7/19/2012 11:50 AM, Roy Mendelssohn wrote:
Hi All:

I have asked this before and am not certain that I ever got a response.  For 
TDS 3.0 is it correct to assume that scan aggregation is deprecated and we 
should be using feature collections for aggregation instead?
Hi Roy:

Yes correct, though we are still debugging the FMRCs in 4.3.

For GRIB files, you really want to use feature collections , type = GRIB.

4.3.12 is the last alpha, next release will be beta. It should be ready this 

Would appreciate use and feedback.


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