3D coverages in WMS

[Dimitar Misev]

WMS doesn't seem to support 3D coverages? It would be useful to allow them in some way, perhaps by a mandatory rasql style. E.g. consider this example:

Change detection by putting NDVI indexes of different dates in each band of the output; tyrol_6 is a landsat cube with 6 time slices:

	for c in (tyrol_6) return encode(
	{
		red:   (((c.nir - c.red) / (c.nir + c.red))[ansi("2015-08-20")] * 255);
		green: (((c.nir - c.red) / (c.nir + c.red))[ansi("2015-07-19")] * 255);
		blue:  (((c.nir - c.red) / (c.nir + c.red))[ansi("2015-06-17")] * 255)
	}, 
	"png")

rasql fragment:

    { (($Iterator[*:*,*:*,5].3 - $Iterator[*:*,*:*,5].2) / ($Iterator[*:*,*:*,5].3 - -$Iterator[*:*,*:*,5].2)) * 255, (($Iterator[*:*,*:*,3].3 - $Iterator[*:*,*:*,3].2) / ($Iterator[*:*,*:*,3].3 - -$Iterator[*:*,*:*,3].2)) * 255, (($Iterator[*:*,*:*,1].3 - $Iterator[*:*,*:*,1].2) / ($Iterator[*:*,*:*,1].3 - -$Iterator[*:*,*:*,1].2)) * 255 }

[Alex Dumitru]

Actually the model supports it already with both time and other dimensions in a standardized manner.
The missing part is in the import from WCS coverage to WMS layer. It would be a couple of days work at most and many users seem to like the idea so maybe we could add it in one of the next sprints?

[Dimitar Misev]

That would be great.

[Bang Pham Huu]

beside the RasqlFragments in Insert Style from Dimitar, there is also a official parameters which support multi-dimensional coverage (max to 4D) in WMS 1.3 is: time and elevation. So it need to be handled as well, here is an example from WMS 1.3 document.

VERSION=1.3.0 
&REQUEST=GetMap 
&LAYERS=ozone 
&CRS=CRS:84 
&BBOX=-180,-90,180,90
&WIDTH=600
&HEIGHT=300
&ELEVATION=1000
&TIME=2000-08-03
&FORMAT=image/gif

e.g: the time parameter can be interval (e.g: 1950-01-01:1950-01-06) or list of dates (2008-01-01,2008-01-05,2008-01-08), elevation parameter should be work the same.

[Bang Pham Huu]

I'm investigating the code WMS 1.3 to migrate to Spring. Actually, it is easy to support 3D, 4D in WMS as it does not import any collections to Rasdaman. WMS stored the Dimension model about the different axes besides X, Y axes. Then when a request from WMS with Time axis or other kinds of axes, it will work as same as WCS subset.

There are 2 cases:

+ Slicing on other axes (e.g: Time="1950-01-01T02:03:05Z"&Heigh=500), return only 1 PNG image.

+ Trimming on time axes (e.g: Time="1950-01-01T02:03:05Z/1950-01-31T03:05Z"&Heigh=500), return only 1 PNG image from all the dates which are overlayed (for example: There are 10 dates from this time interval, so WMS needs to generate a rasql query which using overlay operation for 10 time value (0:9)).

Examples about WMS with slicing Time: ​http://bobtorgerson.github.io/Leaflet-WMS-Time-Slider/

Example about WMS with trimming Time: ​https://boundlessgeo.com/2015/03/using-wms-time-explore-data/

[Bang Pham Huu]

@pbaumann: WMS 1.3 specified about nD+ for WMS ​http://portal.opengeospatial.org/files/?artifact_id=14416

So this enhancement for WMS in petascope was standardized and it could be implemented.

7.3.3.12 TIME
The use of Time values is specified in 6.7.6 and in Annexes C and D.
7.3.3.13 ELEVATION
The use of Elevation values is specified in 6.7.5 and in Annex C.
7.3.3.14 Other sample dimensions
The use of sample dimension values is specified in 6.7.7 and in Annex C

[Bang Pham Huu]

As Peter agreed to process, I'll check this ticket next week.

[Bang Pham Huu]

How to use WMS on 3D+ coverage: ​http://rasdaman.org/wiki/WMSGuide#a3DcoverageasWMSlayer