[Liblas-devel] Metadata [was: Specification for point dimensionality]

[Mike Grant]

On 12/03/10 13:47, Howard Butler wrote:
> On Mar 12, 2010, at 6:31 AM, Mike Grant wrote:
>>  - GDAL's XML format for describing data (see the fields section)
> 
> Heh, VRT's actually my counter-example.  It's home-grown, it doesn't have a schema to validate against, it can't live in a namespace, and it makes up its own names for everything.
> 
>>  - CF Conventions for netCDF data (bitfields section)
> 
> ooh, I hate netCDF's approach :)  

Guess that's some ideas on what to avoid then ;)

>> On a vaguely related note, it'd be nice to have a VLR XML (ISO) that
>> described the dataset for archival and metadata purposes.  
> 
> Have an example?

I don't have a sample lidar one to hand, so wandered over to
http://www.fao.org/geonetwork/srv/en/main.home and searched for "lidar".
 I got something "The Direct Observations of Large Aerosol Radiative
Forcing in the Himalayan Region" - if you open up the metadata popdown,
you can see a pretty-printed version of the XML you can get by clicking
the document icon ("save as xml").  A direct link to that xml is:
 http://www.fao.org/geonetwork/srv/en/iso19139.xml?id=34218

The whole ISO 19139 (19115) thing is pretty complicated but it seems to
be the way things are moving for metadata - it's mandated in Europe
(INSPIRE directive) and the Federal Geographic Data Committee seem to
have picked it up too:
 http://www.fgdc.gov/metadata/geospatial-metadata-standards#isometadata

A high level mention of similar standards:
 http://marinemetadata.org/guides/mdatastandards/comstds
  (DIF is super easy if you want simpler)

The reason we're interested in it long term is that we're supposed to
provide proper metadata when archiving data to a centralised UK data
repository.  We can do this as a separate file, but it'd be ultimately
nicer (and safer) if the metadata is embedded into a single
self-describing file, like netCDF does for model and satellite data.

It may be something for a prospective LAS 1.4 group to discuss, but an
optional XML VLR for dataset description sounds sensible, and
ISO-compatible XML seems the most obvious choice.

Cheers,

Mike.

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