Checksum errors

Microwave Toolbox Problem Reports
#1

I am experiencing checksum errors on repeated downloads of various images. Lately I have had to throw away many images and start again. Since I can only download a limited number of images in a day because of slow Internet, this means a sincere wastte of time. Has anyone else had this problem. I download a GRD or SLC file in .zip. I use WinRAR to Extract the file as \longfilename\ and invariably there is an error in the .zip related to the checksum. So I redownload the same image, and voila, I have the same error with the same file. What to do? Are there other options to download data? Does someone check the zip files to see if they have errors? Thanks. Peter

#2

This question is not related to the SNAP or S1TBXToolbox, is it? It’s posted in that forum.

But I have the same issue with batch download from scihub if it is this what you mean

#3

If the downloaded file is simply incomplete (that is, the number of bytes on disk is less than the expected contentLength property shown in the product metadata), then you could try resuming the download with wget.

For example:

wget --continue "https://scihub.esa.int/dhus/odata/v1/Products('876d5c32-1324-4a0d-aba8-3959ef80d179')/$value" -O S1A_EW_RAW__0SSH_20150708T074549_20150708T074658_006716_008FDC_0A8F.zip

Of course, if you do this, you will probably want to test the zip file’s integrity or check that its computed MD5 checksum matches the one provided in product metadata afterwards.

#4

I have exactly the same problem, with my S-1 download script. I keep re-downloading the same file and i get errors once with the VV image once with the VH image and once with both. This is so annoying and keeps my Internet connection busy 24h 7days a week.

#5

Then for solve this problem the only possible solution is re-download the data until it will work? Any suggestion of software that can handle this during the download?

Thanks!

#6

I have not solved the problem, but I noticed something that became useful. I noticed that the checksum error problem, though always occurring with some files, was not always happening in the same file at the same place. So, with one recalcitrant dual-pol file recently, I found that I could gain access to the compressed data if I told the uncompress program (Winrar) to save broken files in its advanced settings (I learned about this on a hacker site). The checksum errors still occur, but in this way, I found that I could still get access to the data. In this case, the vh band was in one download and the vv band was successfully downloaded in another. I do not know the source of the continuing error, but may be a potential work-around for some people.