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Author Topic: Corrupt/bogus downloads from the National Map  (Read 4830 times)

Boyd

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Corrupt/bogus downloads from the National Map
« on: January 10, 2013, 11:12:04 AM »
Generally speaking I like the National Map better than the old seamless server. But I have found some bugs/anomalies. I have been downloading NED 1/9 arc second data using 24k reference polygons. Some of the downloads result in corrupt zip files ~800kb that can't be opened (a proper download would be in the 50-60MB range).

I don't think these are failed downloads, they are just quads for which no data is available. But the data selection dialog claims that 2011 NED 1/9 is available. These are areas where no data was available a couple years ago when I started collecting the NED 1/9, so again it isn't surprising. But you have to go through the whole process of ordering and downloading only to get the little garbage file.

Some of the 2011 NED 1/9 is actually available for download, but it's a crapshoot and the only way to find out is the make the download attempt. No big deal, just a small annoyance. I wonder if the 2011 data is actually available but they just haven't put it all online yet?

Anyone else see these kind of glitches with the National Map?
« Last Edit: January 10, 2013, 11:14:35 AM by Boyd »

Boyd

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Re: Corrupt/bogus downloads from the National Map
« Reply #1 on: January 10, 2013, 12:05:39 PM »
Update: my assumptions above must be wrong. I had 4 quads to download today and the first one failed. But the other 3 downloaded fine. Thinking 3 out of 4 wasn't bad, just for fun I re-submitted the request of the failed download (from scratch, getting a new e-mail). And now it is in the process of downloading with a size of 55MB.

So maybe sometimes the data extraction process fails and produces a corrupt file?

Boyd

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Re: Corrupt/bogus downloads from the National Map
« Reply #2 on: January 11, 2013, 09:55:29 AM »
Doesn't seem to be much interest in this, but I will close the loop with one final post in case it helps somebody in the future. Got a couple of these same corrupt 800kb files again today and one 55MB file that also wouldn't open.

The trick seems to be DON'T CLOSE the window that says the data is ready until your download is completed and you verify that it can be opened. Clicking the link to retrieve the package in that window seems to work if the initial attempt fails. I believe the system gives you one hour to try again if needed.