Petascope - WCPS encode regular time axis shifted by 6 days with netCDF encoding

[Bang Pham Huu]

To reproduce, import a 3D coverage with time series regular recipe (time axis is regular, resolution is 1 day) in a month (2015-01-01:2015-01-31) from tiff files (each tiff is a day):

{
  "config": {
    "service_url": "http://localhost:8082/rasdaman/ows",
    "default_crs": "http://abc.secore.net/def/crs/EPSG/0/4326",
    "automated": true,
    "track_files": false
  },
  "input": {
    "coverage_id": "test_encode_netcdf_daily_regular",
    "paths": [
      "SCALED*.TIFF"
    ]
  },
  "recipe": {
    "name": "time_series_regular",
    "options": {
      "time_start": "2015-01-01",
      "time_format": "auto",
      "time_crs": "http://localhost:8080/def/crs/OGC/0/AnsiDate",
      "time_step": "1 days",
      "tiling": "ALIGNED [0:0, 0:999, 0:999]"
    }
  }
}

Then run this WCPS query:

for $c in (test_encode_netcdf_daily_regular) 

return encode ( scale($c[ ansi("2015-01-06T00:00:00.000Z":"2015-01-30T00:00:00.000Z")] ,
{ansi("2015-01-06T00:00:00.000Z":"2015-01-08T00:00:00.000Z"), Lat(-90:90), Long(-180:130)}), "netcdf")

The output of netCDF with lower bound for time axis is shifted by 6 days (not according to the value for "2015-01-06T00:00:00.000Z")

[Bang Pham Huu]

This happens due to the fact, in petascope, it shifts by half grid pixel for netCDF encoding. After scaling, time axis's resolution changed to 12 (geo bounds don't change, grid bounds changed).

"2015-01-06T00:00:00.000Z" + 12 / 2 = shifted by 6 days

@Vlad: what is your opinion for this case?

[Bang Pham Huu]

The problem was about the fact "pixelIsPoint" (middle of pixel) in netCDF.