WCST doesn't save null values in coverage

[Vlad Merticariu]

It appears that WCST saves the coverage nil values in the rasdaman array type, but the do not appear in the coverage description, or in the tiff file, when a GetCoverage request is performed.

[Bang Pham Huu]

I will take this ticket as it is good for understanding wcs-t, when ingesting new coverage, it will check if there is an existing type which has the same null value from wcst_import, if not it will create a new type for this null value.

CREATE TYPE OLfFELVjWjmAVXcrYfmSPvXJrUiuZh 
AS SET (KKwlWkvTFnvZGkbYFeFOoMZWEMVify NULL VALUES [99999:99999]

what was missed is ingesting null value to coverage metadata and when DescribeCoverage or Get Coverage, it can show these values in Range List, example:

<swe:field name="Red">
	<swe:Quantity definition="">
		<swe:description></swe:description>
		<swe:nilValues>
		     <swe:NilValues>
			   <swe:nilValue reason=""> 20 </swe:nilValue>
			   <swe:nilValue reason=""> 30 </swe:nilValue>
   		     </swe:NilValues>
		</swe:nilValues>
	        <swe:uom code="10^0"/>
        </swe:Quantity>
</swe:field>

and with GetCoverage in WCS (i.e: tiff file) it should keep the setted nodata value in the tiff tag

service=WCS&version=2.0.1&request=GetCoverage&coverageId=test_nodata_tiff3&format=image/tiff

for example

Band 1 Block=886x9 Type=Byte, ColorInterp=Gray
  NoData Value=200