Wavelet Transform Decompression Software (xRITDecompress)

As mentioned earlier the files you receive from EUMETcast are compressed (unlike the test data you have used so far) and will require extracting before you can use them in SAFNWC. The files are downloaded every 15 mins via the antenna will look something like this like this (over 100 files for every time slot).

H-000-MSG4__-MSG4________-_________-EPI______-201901010000-__

H-000-MSG4__-MSG4________-HRV______-000001___-201901010000-C_

H-000-MSG4__-MSG4________-HRV______-000002___-201901010000-C_

H-000-MSG4__-MSG4________-HRV______-000003___-201901010000-C_

...

...

...

H-000-MSG4__-MSG4________-WV_073___-000005___-201901010000-C_

H-000-MSG4__-MSG4________-WV_073___-000006___-201901010000-C_

H-000-MSG4__-MSG4________-WV_073___-000007___-201901010000-C_

H-000-MSG4__-MSG4________-WV_073___-000008___-201901010000-C_

The 2 characters at the end of the file name are the compression and encryption flags (C and E respectively, underscores for both if file has been decrypted and decompressed). Files downloaded successfully via the antenna setup previously described will mostly be compressed (none should be encrypted).

There is a tool available from EUMETSAT called the Wavelet Transform Decompression Software (commonly referred to as xRITDecompress) this software is used to decompress SEVIRI (and other geostationary satellite) High Rate Information Transmission (HRIT) data files. There is a public Git repository for the decompression software that can be found here. Visit this webpage and download the source code. This will be either zipped or tarred and includes everything needed to decompress the incoming HRIT files from the satellite dish.

To use xRITDecompress this you will need to compile the program from source. First move the .zip/.tar/.tar.gz/.tar.bz2 file (here we assume you have chosen the .zip file) to the location where you wish to store the wavelet decompression software and unpack it. In this example we will be compiling the executable in your safnwc directory.

mv PublicDecompWT-master.zip $SAFNWC/.

cd $SAFNWC

unzip PublicDecompWT-master.zip

Now navigate to the xRITDecompress directory within the newly created PublicDecompWT-master directory. Once there, assuming that you have the appropriate software (g++, make, ar and ranlib; all should already be on your system) you will be able to compile the xRITDecompress executable.

cd PublicDecompWT-master/xRITDecompress

make

you should now see an executable file called xRITDecompress

To use this command you need to do the following

./xRITDecompress filename

However, as you are aware there will be a large number of files being produced every 15 mins. Therefore it makes sense to write a short script to decompress lots of files at once. We will write script later in the tutorial when we have compressed data to work with. For now just check that you have produced an executable in the PublicDecompWT-master/xRITDecompress directory.