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Are they jamming GPS, or just turning it off over that area? Sort of hard to tell reading that article.
by madengr 9y ago
Are they jamming GPS, or just turning it off over that area? Sort of hard to tell reading that article.
- itronitron 9y agothey wouldn't be able to turn it off over a single geographic area as the GPS satellites are broadcasting from space but they might be able to turn Selective Availability (SA) on for individual satellites however that would downgrade the signal received by every GPS receiver in view of the satellite until they turned SA back off
- tialaramex 9y agoModern GPS satellites don't know how to do Selective Availability, this feature was not being used, so implementing it in spacecraft (which is not free) made no sense and new birds aren't fitted with it. Newer models of GPS satellite implement a new variant of COSPAS-SARSAT instead, unlike a Geostationary satellite they pass over the whole Earth's surface, so they can see your rescue beacon from anywhere, and unlike the weather satellites used in the past to cover the whole surface they have powerful transmitters in the right frequency range already, so they could reply. Today (in testing only) this means faster rescue after triggering a beacon. Search and Rescue resources will know where you are (often to within metres) just minutes or even seconds after you activate the beacon, an improvement on prior models (10+ minutes on most of the surface, up to hours nearer the poles) and eventually new beacons will be able to tell you that rescue is coming perhaps with short text or coded messages e.g. "Mountain patrol on their way. ETA 48 minutes. Stay where you are if safe."