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As a Tokyo dweller, I'm also quite excited about the QZSS system which has a constellation of 4 satellites one of which is always in a near zenith position and
by GolDDranks 8y ago
As a Tokyo dweller, I'm also quite excited about the QZSS system which has a constellation of 4 satellites one of which is always in a near zenith position and provides a GPS signal even amidst the highest skyscrapers.
- londons_explore 8y agoThe thing is... One satellite isn't enough to get a position fix... You need at least 4 (or 3 if you want a very rough position fix and are happy to assume your altitude = ground level) So effectively, this QZSS system provides 1 extra satellite over what GPS would normally have visible - which is helpful, but really just an incremental improvement.
- GolDDranks 8y agoAh, dang. You are totally right. Well at least I welcome the incremental improvement. GPS sometimes really struggles where I work.
- jamiek88 8y agoYes but that increment massively increases the utility on the ground so sometimes baby steps mean huge useability leaps.
- mikeash 8y agoThe geometry of those satellites matters a lot, especially when you have tall buildings in the way. Always having one more or less straight overhead is a pretty big improvement.
- moftz 8y agoQZSS adds one geosynchronous and three tundra orbit satellites so depending on where you are in the city, you could be seeing two or more QZSS satellites. It's not going to replace GPS but its going to help with getting a quicker location solution than not having it. Something where you have beacons on every major intersection would be a better step for a city to introduce. The beacons would just be sending compatible messages so there is no need for additional hardware. If the roads are straight enough, you could see multiple beacons plus whatever satellite is overhead.