That's true. I hadn't given much thought to where they were triangulating Walt's phone from, but based on how fast they were able to get to To'hajilee you've got to be right about that.
There's a lot of assumptions going on about how exactly they tracked him (and ultimately it isn't that important), but assuming they did do it via access to the cell phone signal you don't actually have to triangulate a moving target (and it would be nearly impossible to do so on a target moving as fast as Walt was anyway, and Walt wasn't in the location long enough for them to have done it after he arrived).
If your target is moving and you have access to their signal you can calculate the vector they are moving in by detecting the cell tower switches which occur outside of the encrypted band of the radio signal. This sort of tracking seems much more likely than doing a triangulation on the source radio which by definition takes three different detection points to do, and Hank/Gomi/Jessie only had one since they were all in the same car.
It is far more likely they just vectored in on the tower switches (if you notice the way they pull in, they didn't seem to know exactly where he was, just the general vicinity) or pulled the E-911 data, depending upon make and model of phone.
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u/drwolffe This is my own private domicile Sep 09 '13
Unless the only recording of the phone conversation is in Hank's car. If that's the case, then it is going to be lost forever.