Originally Posted by
beep88
iPhone or standalone GPS are not super reliable for walking in the city, especially Tokyo with tall buildings and narrow side streets, as GPS requires line of sight to the sky and mutiple satellites are required for correct positioning.
If you are walking along wide boulevards or crossing parking lots or public parks, then yes it's excellent.
I used google maps (with a local data plan) and MapFan (Japanese standalone GPS app that requires no data) trying to access certain addresses and neither of them is very good. It typically lacks behind by 500m or so.
At least with google maps you can use street view to see the actual neighbourhood or things along the route.
500 m is an exaggeration; a few 10s of meters at best. I use my Google maps on my iphone as a back-up for car navigation without a problem and it works flawlessly all over Tokyo except tunnels. It even seems to work ok when you are on Roppongi dori with the expressway above. There is a slight lag of a fraction of a second but you easily compensate.
Since most tourists are not driving around Tokyo, I am sure they can manage.
The Navi in my car even works below ground in the Yamate tunnel, for example.