From Newsgroup: comp.mobile.android
Marion wrote:
Obviously I'm aware that the voice radio is needed for calls & that the cellular data radio is desirable for online maps/traffic, and that the bluetooth radio might be used for speakers, etc., so explicit tradeoff choices that most of us must make as a result will be discussed later.
Marion wrote:
This is my first-pass best-guess comprehensive method to obtain as close to Garmin-style location privacy as we can get on a non-rooted Android phone.
Obviously I'm aware that the voice radio is needed for calls & that the cellular data radio is desirable for online maps/traffic, & that the bluetooth radio might be used for speakers, etc., so explicit tradeoff choices that most of us must make as a result will be discussed later.
Of course, our first pragmatic choice from ultimate location privacy
is are the pragmatism of voice radio & the cellular data radio settings.
Likely most of us will trade location privacy for cellular voice
capability.
Likewise, most of us will trade location privacy for traffic & online maps.
Below are the privacy ramifications to help each of us make that choice.
Location radio = ON
This is the MASTER SWITCH for location data if we want GPS at all.
If it's turned off OFF, no GNSS fixes are possible.
So the location radio is essentially not optional when we're routing.
Voice radio (cellular voice):
Mandatory if we want to use the phone as a phone.
Without it, no calls, no SMS, no emergency dialing.
So this radio is not optional in practice.
Cellular data radio:
Mandatory if we want live online maps, traffic, search, etc.
We can work around it by pre-downloading offline maps,
but most people need data for daily use.
So this radio is also not optional for most users.
Here's an assessment of relative accuracy of our various choices:
GPS only: a few meters outdoors, but poor indoors.
Towers only: hundreds of meters to kilometers.
Fused provider with Wi-Fi/BT: tens of meters, sometimes better.
Voice radio (cellular voice) = ON
Benefit:
We can make & receive calls & SMS.
The phone maintains a constant connection to the nearest tower.
Tradeoff:
The network always knows which tower we are connected to.
This gives a coarse location (hundreds of meters to a few km).
Location accuracy depends on tower density (urban vs rural).
Even with data OFF, tower registration still happens.
Voice radio (cellular voice) = OFF (airplane mode)
Benefit:
No tower registration, so there is no tower-based coarse location.
This provides maximum location privacy from the cellular network.
Tradeoff:
No calls, no SMS, no emergency dialing.
What if we are in a rural area, where it's a single-tower connection?
Then, the network always knows which tower our phone is registered to.
That gives only a rough circle around the tower, often 1�V20 km radius
depending on rural vs urban density.
What if we're near multiple towers (where triangulation is possible)?
If our phone is in range of several towers, the carrier can use
timing advance, signal strength, & angle-of-arrival techniques
to narrow our position.
In cities with dense towers, this can shrink to a few hundred meters.
In rural areas with sparse towers, it may still be kilometers.
what about emergency services (E911 in the US, similar elsewhere)?
Regulations require carriers to provide more accurate location
for emergency calls. This can involve tower triangulation plus
requesting GPS from the handset if available.
Accuracy can be 50 m or better in urban areas.
This can not be turned off as it has a deeper-level of OS access.
And then there's the all-encompassing worst-case "fused provider"...
Google fused provider (when Location Accuracy is ON):
Uses GPS + Wi-Fi AP beacons + Bluetooth beacons + cell towers. Yikes!
Wi-Fi APs: SSID/BSSID + signal strength, matched to Google��s database.
Accuracy often 10�V30 m in cities with dense Wi-Fi.
Bluetooth beacons: advertising packets, matched to database.
Accuracy can be a few meters indoors if beacons are known.
GPS: adds satellite fixes, usually 3�V10 m outdoors.
Combined result: often <10 m in urban areas, much better than towers alone.
Obviously, for location privacy, having the fused provider on, is bad news.
And yet, for most people, it's likely on all the time. Sigh.
What happens when we turn on the cellular data radio?
Cellular data radio = ON
Benefit:
We can load online maps, traffic, search, weather, etc.
Apps that expect constant connectivity will work normally.
Tradeoff:
The carrier can see our data sessions & tower locations.
Network-assisted location (A-GPS) may be used, which means
the phone can request satellite almanac/ephemeris data
from the network instead of waiting for the GPS chip alone.
Google or other apps can send/receive location data in real time.
Cellular data radio = OFF
Benefit:
No network-assisted location (GPS runs "cold start" only).
No data sessions visible to the carrier.
Reduces the chance of apps leaking location over the network.
Tradeoff:
Online maps will not load new tiles.
Navigation apps may fail unless we pre-download offline maps.
Other apps that rely on data will not function.
--
Understanding the issues is important because details are what matter!
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