OT How does GMaps know elevation?

[Swer]

Because the laser is the most accurate way to measure things.

GPS doesn't. It used radio waves.

Yes.

[Swer]

It's a direct ping from the satellite or plane with the laser. With GPS its continuous radio waves with varying propagation effects. That's why you need more than one visible satellite with GPS.

[rbowman]

A GPS receiver extrapolates from the satellite constellation. The closer to the horizon the birds are and the more angular distance separating them, the better it works. In cities or mountainous terrain the view of the sky can be limited so it has to work with those overhead. It has nothing to do with light unless you have an extremely loose definition of the spectrum.

With a laser you're bouncing the beam off an object.

[Mike Coon]

Wavelength.

Mike.

[Mike Coon]

Did your mummy say "Because I said so!" a lot?

Mike.

[Rod Speed]

Nope, it's a laser pulse from the plane or satellite, travel time measured.

GPS is continuous transmission with digital encoding on that.

[Swer]

Mike Coon [e-mail]> wrote

Nope, both mum and dad quickly worked out that doesn't work with me.

I still remember the mega stoush that happened when I refused to eat something like spinach. She never tried that again.

[Jim Joyce]

I live in a new development and after being here for about 5 months, Google Maps still didn't show any streets out here at all so I submitted all of the streets as map updates. About 4-5 days later, Google emailed me, thanking me for the updates. I immediately checked the map and the streets were all there, just as I had drawn/described them.

I tried to do a second update, this time adding the house numbers, (there are currently 27 houses built, with more partially built), but Google replied, telling me that house numbers would have to wait until the next (actually the first) time the Google car comes through the area.

Meanwhile, with streets on the map but no house numbers, navigating to any house number on my street will get you to the same spot, midway along the length of the street. It's better than nothing.

[Ed Pawlowski]

My street is at leat 18 month but is not on any navigation yet. My car nav will take me to an open field about 1/4 mile from my house, then I have to walk home.

[Jim Joyce]

The car nav is basically hopeless, but Google Maps turned out to be easy.