I was getting fed up with the total flakiness of my phone's GPS, so I had a hunt on the web, in case there was a software patch. I found this totally surprising advice:
I tried it, took my phone outside and got a fix immediately.
Some important caveats:
* I haven't tried it in proper use yet
* This fix involves the use of what my husband calls a "warranty voiding tool" - ie a screwdriver. Most mobile phone company's really discourage this sort of thing, and I take no responsibility for any damage anyone causes !
No-one seems to know why it works but it seems to. My phone is an S3 mini.