Dimensionality of Datacube vs Output Format

[przell]

@aljacob and me have seen that the dimensionality limits the choice of the output format. @prateekbudhwar could you check this:

• JSON: works for all dimensionalities of datacubes
• GTiff: works only on 3d datacube. This is ok.
  • It should be tested though what happens when x,y,t is given and when x,y,b is given. Is t or b treated equally when only 3 dimensions are available?
  • An error message for the user would be great if 3d is exceeded.
• NetCDF: Doesen't work on 3d datacube. Only works on 4d datacubes. It should also work on 3d.

Here are two example process graphs. By changing the output format between GTiff and NetCDF it should become clear where the problem is.

Process Graph 3d:

{
  "load_collection_PRVZO1091D": {
    "process_id": "load_collection",
    "arguments": {
      "id": "GEOtop_snowdepth",
      "spatial_extent": {
        "east": 10.4,
        "north": 46.86,
        "south": 46.85,
        "west": 10.39
      }
    }
  },
  "reduce_dimension_YFXPQ1884B": {
    "process_id": "reduce_dimension",
    "arguments": {
      "data": {
        "from_node": "load_collection_PRVZO1091D"
      },
      "reducer": {
        "process_graph": {
          "max_KCVBW1216O": {
            "process_id": "max",
            "arguments": {
              "data": {
                "from_parameter": "data"
              },
              "ignore_nodata": true
            },
            "result": true
          }
        }
      },
      "dimension": "DATE",
      "context": null
    }
  },
  "save_result_GEDQJ8327V": {
    "process_id": "save_result",
    "arguments": {
      "data": {
        "from_node": "reduce_dimension_YFXPQ1884B"
      },
      "format": "GTiff",
      "options": {}
    },
    "result": true
  }
} 

Process Graph 4d:

{
  "load_collection_XXMQU6188U": {
    "process_id": "load_collection",
    "arguments": {
      "id": "GEOtop_snowdepth",
      "spatial_extent": {
        "east": 10.4,
        "north": 46.86,
        "south": 46.85,
        "west": 10.39
      }
    }
  },
  "save_result_PNWYS7148M": {
    "process_id": "save_result",
    "arguments": {
      "data": {
        "from_node": "load_collection_XXMQU6188U"
      },
      "format": "GTiff",
      "options": {}
    },
    "result": true
  }
}