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<blockquote data-quote="MacInWin" data-source="post: 1827179" data-attributes="member: 396914"><p>Elevation is not critical to road navigation and it adds a lot of extra data to have 3D maps. All the terrain information has to be added to the lat/lon info already there for 2D. That extra data adds about 50% to the size of the files with the maps. In addition, altitude is the most unreliable aspect of GPS. The challenge is that all of the satellites are on one side of you (above you) so there is a natural bias in the calculations. By the time a satellite is low on the horizon and useful for altitude, the error induced by the signals travelling through a lot more atmosphere makes them more unreliable overall. It's a lot better now than it was in the "early days" when you could be at the beach, literally at sea level and have the GPS report anywhere from +500 to -500 feet. </p><p></p><p>I used to have a 3D mapping system. I don't remember the name, but the map sizes were huge. It was kind of cool to be driving up a valley and see the hills on either side on the screen, but to be honest, the terrain information just wasn't useful for road navigation.</p><p></p><p>EDIT: If the system you use has a screen to show lat/lon, it should also show elevation. But again, the maps are 2D for the most part.</p></blockquote><p></p>
[QUOTE="MacInWin, post: 1827179, member: 396914"] Elevation is not critical to road navigation and it adds a lot of extra data to have 3D maps. All the terrain information has to be added to the lat/lon info already there for 2D. That extra data adds about 50% to the size of the files with the maps. In addition, altitude is the most unreliable aspect of GPS. The challenge is that all of the satellites are on one side of you (above you) so there is a natural bias in the calculations. By the time a satellite is low on the horizon and useful for altitude, the error induced by the signals travelling through a lot more atmosphere makes them more unreliable overall. It's a lot better now than it was in the "early days" when you could be at the beach, literally at sea level and have the GPS report anywhere from +500 to -500 feet. I used to have a 3D mapping system. I don't remember the name, but the map sizes were huge. It was kind of cool to be driving up a valley and see the hills on either side on the screen, but to be honest, the terrain information just wasn't useful for road navigation. EDIT: If the system you use has a screen to show lat/lon, it should also show elevation. But again, the maps are 2D for the most part. [/QUOTE]
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