Test nectdf import + export

[Vlad Merticariu]

Task is:

• download the attached netcdf file and inspect them in a netcdf client (e.g. panoply)
• import the netcdfs into rasdaman (either 1 band at a time, or several bands)
• export the data from rasdaman in png and netcdf
• inspect the results using the same client, check that the files resulting from rasdaman are the same as the original

Examples on how to import netcdf data in rasaman can be found in systemtests/testcases_mandatory/test_netcdf

[Vlad Merticariu]

netcdf file can be found here:
​http://flanche.net/geodata/nc-201003.nc
​http://flanche.net/geodata/nc-201004.nc

[Dimitar Misev]

Here's some more sample data: ​https://rsg.pml.ac.uk/shared_files/olcl/data_for_vlad/

Incl. wcst_import ingredients :

• this is a multi band insitu : ​http://pastebin.com/C9bhSiB7
• this is a single band insitu : ​http://pastebin.com/HCyQc3W7

[Bang Pham Huu]

netcdf compare to png

[Bang Pham Huu]

I see there is a patch for this ticket was uploaded in patch manager and it was failed. The change in this patch with calculation of the Lat (negative direction) leads to different subsets (netCDF is top and PNG is bottom).

​http://rasdaman.org/attachment/ticket/1409/upsize_down.png

So I'll take this ticket and check it a bit more careful, thanks Drusu for doing it first.

[Bang Pham Huu]

So the problem with the reversed image is invalid, sorry, (because the netcdf was flipped then I saw wrong direction, checked by Vlad).

There is a problem now is the netCDF when do subsets (e.g: Lat(-45:45) is missing value 0, then it is shifted by 1 pixel).
e.g: subsets

45, 35, 25, 15, 5, -5, -15, -25 ;

e.g: the unsubsetted result:

 90, 80, 70, 60, 50, 40, 30, 20, 10, 0, -10, -20, -30, -40, -50, -60, -70, -80 ;

[Bang Pham Huu]

@Vlad: if we write the Lat axis top-down (90, 88, … -90) it will be mirrored in Panoply. If write bottom up (-90, -88, … 90) then it display correctly.

​http://rasdaman.org/attachment/ticket/1409/netcdf_mirror.png

[Vlad Merticariu]

It doesn't matter. As you see in the left-hand side image, panoply believes that the north pole is at -90 degrees, which is false.

Bottom up is correct for linear negative axes.

[Bang Pham Huu]

Yes, but in the patch for this ticket it writes top-down (which is in the right-hand side image), then I fixed it to write bottom-up (left-hand side image), you see in both case Panoly displays bottom-up (North is -90 degree in axis number).

[Vlad Merticariu]

The way the image is written by the patch is correct.

Right-hand side = correct

Left-hand side = incorrect

[Bang Pham Huu]

Replying to vmerticariu:

The way the image is written by the patch is correct.

Right-hand side = correct

Left-hand side = incorrect

yeah, I just realize what you meant after comment, you are rightthanks.

[Bang Pham Huu]

I imported the file ​http://flanche.net/geodata/nc-201003.nc with this recipe ​http://pastebin.com/C9bhSiB7

then compare in Panoply (left is encoded netCDF output, right is the input file). There are different

​http://rasdaman.org/attachment/ticket/1409/diffrent_netcdfs.png

+ the left image is shifted by 0.21 degree.
+ the left image null value should be -999999 and in recipe set nilValue.
+ also it has an extended bound > -90 (Lat) and > 180 (Long), (not sure it was fixed).

    Lat (measured in degree ) with domain extent from -123.33333333347065 to 90.00000000003335.

    Long (measured in degree ) with domain extent from -180.00000000033336 to 203.99999999997385.

[Bang Pham Huu]

@Vlad: in ​http://rasdaman.org/ticket/1409#comment:5 I meant it missed the 0 value, actually, due to the formula current in NetCdfDecodeFactory:

for (i = 0l i < points; i++) {
 if (axisDirection > 0)
     coord = geoDomMax.subtract(resolution * i)
 else 
     coord = geoDomMin.add(resolution * i) 
}

So if I have a coverage with offset vector is (Long: 10,Lat:-10) and bounding box: (Lat: -90: 90, Long: -180:180), then I subset: Lat(-20:15), it returns a coverage with data: Lat = 15, 5, -5 ;

this is wrong coordinates and what need to do is shifted the input subset to correct geo coordinate (​http://codereview.rasdaman.org/D249, wait for your review), so Lat(-20:15) will be shifted to (-20:20) and the netCDF formula above will return data: Lat = 20, 10, 0, -10 ; which is correct points.

[Dimitar Misev]

I guess can be closed.