Why are Differential Correction services unable to transfer files for a 24-hour period?

Question

Over the past year I have gone out and gathered Feature points using a Trimble GPS Device.
When I'm done, I'll come back to the office and try to perform Differential Correction using Pathfinder Office (v5.60).
It seems that quite often I am "Unable to transfer" the files in order to post process and correct my GPS data.
Most research I've done on this topic indicates: "Wait for 24 hours and then try again."
Do I just have bad timing, or are these services regularly not available [whether for updates or servicing]?

The first two are CORS and the third is USDA.

Answer 1

Base stations in the CORS network typically generate base files on an hourly basis, so if you collect your GPS points at 1:20pm, you should be able to download base data to correct them shortly after 2:00pm. At the end of the day, the hourly files are collected into one ZIP file for that day, then the hourly files are deleted.

I'm not 100% sure this is correct but I believe that the fault is with Pathfinder Office. While it has no trouble downloading the daily ZIPs, it has some trouble downloading those hourly files. It's done it successfully for me for some base stations, but not others. I think it has to do with the file naming convention used by the base stations, for some stations PFO gets it wrong and although the files exist, it can't find them because it's looking for the wrong filename. Of course, not all stations upload their base files in a timely fashion day in and day out, so it may be that the files weren't actually there.

To confirm that, you can download the hourly files manually directly from the CORS download site and use them in the differential correction utility instead of the automated download. Just select the CORS base station you're interested in, and the date, and you'll be taken to the CORS FTP site where you'll see a list of that day's files. The hourly files will all have a letter at the end of the filename, "a" for the first hour of the day and "x" for the last.

Also, if you're using the same base station over and over again, and PFO can't download its hourly files, you can circumvent it by adding a custom base station to the list used in the Differential Correction utility, and you can specify there the exact naming convention used for the hourly files:

Click the Help in the following window for details on how to set the naming convention (the Base File Address Format):