VCP in ODIM files is always 0

[peterdesmet]

@adokter we defined Volume coverage pattern (https://aloftdata.eu/vpts-csv/#vcp) as having the following valid values:

12, 212, 112, 215, 121, 31, 32, 35

All BALTRAD files @stijnvanhoey has encountered so far however, have value 0 for VCP and thus fail validation. Can 0 be added to the valid values?

# download https://aloft.s3-eu-west-1.amazonaws.com/baltrad/hdf5/bejab/2022/08/19/bejab_vp_20220819T235500Z_0x9.h5
file <- "bejab_vp_20220819T235500Z_0x9.h5"
library(bioRad)
vp <- read_vpfiles(file)
vp$attributes$how$vcp
# 0

[adokter]

sure that works - vcp codes are mostly used in the US, which is why they are missing in EU files. I just checked the code and in case no vcp attribute is found in the file, a value of zero is returned:
https://github.com/adokter/vol2bird/blob/2810f331f039b9f7a28ad4afe06d1f7bf05ecb2c/lib/libvol2bird.c#L4753
Therefore currently 0 denotes missing

[stijnvanhoey]

@peterdesmet should we keep them as 0 or rather convert them to ""?

[peterdesmet]

“” makes more sense than 0. Can be part of the conversion (cf. 0/1 to FALSE/TRUE).

[adokter]

I can also change vol2bird to store NULL instead of 0, let me know.

@peterdesmet in historical data I have seen a few more VCP codes than the valid values listed above (11, 211, 21, 221, and there might be more). We may want to have the flexibility to assign our own VCP codes at some point for countries that do not have a pre-defined VCP classification. Checking whether VCP is a number may be sufficient.

[peterdesmet]

1. @adokter Would be good if vol2bird set it to NULL, makes more sense to me.
2. @stijnvanhoey conversion to NULL for data with 0 would still be good
3. @adokter ok, I will remove enum.