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Re: Time in WCS




However, the standard response file format for WCS is GeoTIFF, and you probably do not want to put multiple times into a single GeoTIFF file (because while one can put multiple images in a GeoTIFF file, I don't think there is a standard way to label the different images as having different times). It all depends, of course, on what the client can handle, but hopefully the client won't ask for things it cannot handle.

Yes, the major issue here is the standard of delivering the temporal information to clients. GeoTiff does not have such standard and thus a client is expected to know the temporal information it will get. For example, if a client request four days of daily image, it should know that the four images included in the response are for what four days. This, of course, is not a solution to general use cases. The solution is perhaps to develop a WCS profile for GeoTiff, which has been proposed in WCS1.1+. BTW, GeoTiff is just one of the file formats mentioned in WCS1.0.0. Other file formats, especially CF-netCDF, have more standard way in expressing temporal information. Also, for geoTiff, if the resultant data is 3-D, i.e., two spatial and one temporal, then multiple images may not be necessary because the temporal dimension can considered as a "band" dimension. If multiple images are needed, such as data with three spatial dimension plus one or more temporal dimensions, multiple subfiles are needed but TIFF6.0 baseline does not support multiple files. The client's geotiff reader needs to support tiff6.0 extension.


Wenli

At 09:24 AM 7/9/2007, Benno Blumenthal wrote:
Roy Mendelssohn wrote:
While I have your attention, I have not been able to get a straight answer if there is a way to send the WCS request to get a time range, rather than a single time, and if so what is the syntax for that.
Hi Roy,

The default in a GetCoverage response is all available times: you can restrict the times using a TemporalSubset Restriction which lists one or more times or a range.

TimeSequence= 20060801,
20060811, ?
OR TimeSequence = 20060801/
2006-0901 / P1D, ?
Optional, include when
temporal subset desired
other than default b
Request a subset corresponding to the
specified time instants or intervals,
expressed in the extended ISO 8601 syntax
defined in Annex D of [OGC 04-024].
(See 9.3.2.4.)




However, the standard response file format for WCS is GeoTIFF, and you probably do not want to put multiple times into a single GeoTIFF file (because while one can put multiple images in a GeoTIFF file, I don't think there is a standard way to label the different images as having different times). It all depends, of course, on what the client can handle, but hopefully the client won't ask for things it cannot handle.

Benno

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