Using 8.5 Gigabyte DVDs
 

Earlier I wanted to make a backup copy of my navigation update DVD. I was surprised to find that the DVD had about 7.5 GB of data stored on it as I never knew that non-dual layer DVDs were available in this size. (Why am I the last to know?)

A quick online search shows me that several manufacturers make DVDs in the 8.5 GB size. Here is one example on the Staples website: Memorex™ 5/Pack 8.5GB DVD+R DL, Jewel Cases

Will my laptop optical drives that read and write 4.7 GB DVDs be able to use the larger 8.5 ones?

This is dual layer. DL = double layer = dual layer.

Single layer can only do 4.7 (based off of the spec). Dual can do twice.

The navigation update DVD does not look like dual layer; there is a label on one side. Moreover, I don't think my computer's drive reads dual layer.

The two layers are on the same side, just at different depths. the device knows how to focus it's laser on either layer, one at a time.

/dnastudios

Dual layer are not double-sided. Both layers are on the same side -- the laser just refocuses to read the two layers. It's not completely clear whether your laptop drive will burn dual-layer DVDs. Most likely, if it can read double-layers it can write them.

You'll need a dual-layer DVD burner to use these -- I picked up a cheap USB drive that does +R and -R for about $50 on eBay.

My car is very fussy about media, though, and won't read all brands of disks. You may need to do some trial-and-error (or a Google search) to find a combination that works.

You could always just rip the DVD and store the data on a flash drive, if you don't need another physical DVD right away.

I suspect a physical DVD is required for the car's nav system to read it; it would be much preferable if those could be updated via USB, but I've never seen it.

Yup, car navs use DVD's because the dealers have some control over the selling of those discs. No reason why it couldn't use USB's as the hand-helds use flash memory.

It would be even more preferable if they could be updated by cellular. :)

Given how easy it is to download and burn a DVD-R DL with a nav system update, it strikes me that going even easier with the USB and cellular cases has one big risk: the manufacturers putting security on it to help protect dealer revenue. Be careful what you wish for...

(Also, via cell, you'd really need to make it able to download deltas. Updating an entire 4+gb of maps at once would be very expensive.)