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I have noticed that my GPS Map screen reads 150 Ft elevations all the time. Since I just returned from a trip from San Francisco to Colorado and back, and my elevation was a constant "150 Ft," even at 11,000 Ft above sea level, either my GPS is not working, or the GPS system doesn't have elevation info.

Can anyone comment? Thank you.

Going at a cruise-control speed of 79 MPH on US 50, I averaged approx. 50 MPG. On the leg from Reno to SF (which includes a stretch of downhill to Sacramento), I averaged 57.3 MPG for 240 miles.

Thank you,

Joe B
Prius 2004 #9
 

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Joe-
that number is a distance guide...

you see this:

|__150ft__|

That means, that a distance of that length is about 150ft. Note if you zoom out (magnifying glass with a "-" or speak the command "zoom out" It will change numbers, to 300ft, 700 (or it may be 750..., etc)

Hope that helps! :)
 

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I am not familiar with the Prius GPS display (just test-drove one and got on the waiting list), so perhaps the previous poster answered your question.

If not, the GPS system requires 3 satellites to give a position fix in 2 dimensions. This puts you on the map. If 4 satellites are available, then GPS will calculate an elevation as well (3 dimensions). If you were in the mountains, you may not have had 4 good satellite signals for a long enough time to calculate the elevation.

Hope this helps.
 

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OK, I'll jump off the deep end here: My (limited) understanding of GPS was that it worked of timing signals from multiple satellites. From that distance it could determine location in space. With only one satellite, it identifies you are on somewhere on a sphere of fixed radius from that satellite: not too helpful. A second satellite gives a location also on a similar sphere centered on that satellite; these two shperes intersect in a circle, so now the system can narrow it down to somewhere on a circle in space. Pulling in a third satellite gives a third sphere; the three spheres intersect at only two points, and one of those points is not meaningful (deep within the earth, or out in orbit), so the system disregards that point, and can use those three satellites to specify a single point in three dimensional space.

So what's the 4th satellite needed for? cross check?

Tau Zero
 

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the three spheres intersect at only two points, and one of those points is not meaningful (deep within the earth, or out in orbit), so the system disregards that point, and can use those three satellites to specify a single point in three dimensional space.

So what's the 4th satellite needed for? cross check?

Tau Zero
Actually the GPS is really really dumb and does not like to guess much about anything! The 4th Satellite is to confirm the position. My Garmin iQue will give you a zone of accuracy at times when tracking less than 4 satellites. A little or large blue ring around the "car". One of the preferences places the car on the nearest road that is tracing the direction you are going. I can really be funny at time. If the virtual map does not match the real map I get "off rout recalculating". There is one turn near my house where this always happens. On the whole I would not be with out it particularly in a strange town. I often find the data base of location very helpful and will consult it for phone numbers even locally first before I go to the phone book.
The elevation has always been the worse datum. Before the military lock was taken off it could vary by hundreds of feet from step to step. My old hiking gps would have me hundreds of feet underwater at home (elevation 215 feet from the USGS Topo of the area. As you can see I am a map freak. Am I getting a #9! You bet nothing else but. Got to know where I am even in my driveway!
Henry Drygas
 

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bradca21 said:
Joe-
that number is a distance guide...

you see this:

|__150ft__|

That means, that a distance of that length is about 150ft. Note if you zoom out (magnifying glass with a "-" or speak the command "zoom out" It will change numbers, to 300ft, 700 (or it may be 750..., etc)

Hope that helps! :)
This explaination is correct. The number you are referencing is the scale of the map, not your altitude. There is no altitude display with the Prius NAV system.
 
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