https://www.gpsworld.com/how-to-achieve-1-meter-accuracy-in-android/
[partial quote begins]
Recent changes in hardware and standards make one-meter accuracy possible, in
some cases as soon as this year. The transcript of a talk given to Android
developers earlier this year, this article gives a short overview of location
in smartphones, introduces Wi-Fi round-trip time technology and standards, and
then explains the Wi-Fi application programming interfaces.
By Frank van Diggelen, Roy Want and Wei Wang, Android Location, Google
Eventually, this means high accuracy for everyone, but we want to take you
under the hood of location because we want to give you the opportunity to get a
head start on the future. We also want to highlight the need to protect and
respect the user. The more people who use location, the more careful we and you
have to be. We will highlight where you must get user permissions and we’ll
close with some guidelines for making great location apps.It’s a great time for
location applications because technology hardware standards and Android
application programming interfaces (APIs) are all evolving simultaneously to
enable an improved location accuracy that has not previously been possible when
using smartphones.
Where are we today with indoor location accuracy? If you’ve noticed that your
phone seems to be more accurate when you’re inside shopping malls and office
blocks than it was a few years ago, you’re not imagining it. With each release
of the fused location provider, we have had steady improvement of the Android
algorithms and machine learning for Wi-Fi locations.
There continues to be improvement, and you’ll see indoor accuracy of better
than 10 meters, but round-trip time (RTT) is the technology that will take us
to the one-meter level.
Meanwhile, what about GPS? In terms of GPS accuracy in the open sky, there has
not been much change in the last few years. If you’re outside and can see the
open sky, the GPS accuracy from your phone is about five meters, and that’s
been constant for a while. But with raw GNSS measurements from the phones, this
can now improve, and with changes in satellite and receiver hardware, the
improvements can be dramatic.
Everyone’s familiar with the blue dot, but to get the blue dot you need a
location provider, and to get location you need measurements — specifically,
range measurements from Wi-Fi access points or from GPS satellites. We’ll show
you how one-meter measurement accuracy can be made available in smartphones.
The key technologies are Wi-Fi RTT, GPS dual-frequency and carrier phase
measurements.
[end of partial quote]
On Tuesday, January 22, 2019, 11:28:08 PM PST, jim bell
<[email protected]> wrote:
On Tuesday, January 22, 2019, 3:13:07 PM PST, Steve Kinney
<[email protected]> wrote:
On 1/13/19 10:43 PM, Mirimir wrote:
>> Dropgangs, or the future of dark markets
>Here's some ideas about structural vulnerabilities in the Dropgang
protocol, as described at https://opaque.link/post/dropgang/
>Dead drop reuse:
>To achieve acceptable security each dead drop may be used once only,
because hostile buyers could place 'their' dead drops under video
surveillance and record every courier and customer visit to the drop
following their own transaction.
>Couriers delivering to dead drops can not determine if their supplier
sends them to previously used dead drops, unless they service only dead
drops they set up and document themselves. Couriers should transmit the
locations of drops they have developed only when presented with an order
to fill, to assure that their distributor can not send other couriers
and customers to use them first. The added surveillance exposure of
making two visits to the same site - setup and delivery - presents less
exposure than trusting that the anonymous seller will never send a
courier to a previously used dead drop.
[much stuff deleted]
People who think of a 'dead drop' as being a previously-existing hidey-hole in
the urban/suburban landscape need to remember that even if they are relatively
plentiful, they are NOT so plentiful that they won't be reused at some point.
Or much more likely, probed on speculation by passers-by, especially once they
learn that such locations may be used as dead-drops.
This is one reason I previously described my idea to have a pointy metal or
stiff-plastic tube driven into the soil or in grassy area, maybe 1 inch in
diameter, and then filled with a removable tube with the payload contained in
it. For an approximate shape, take a look at this ad for centrifuge
tube:https://www.usplastic.com/catalog/item.aspx?sku=76941&gclid=Cj0KCQiAm5viBRD4ARIsADGUT24x7cDtbtnGyiwG2_DKaCKpwCn9I-jw8XHCOwL17U0LCWFB3SQkyGAaArjUEALw_wcB
(Although I am not suggesting employing an actual 'centrifuge tube': They
appear to be much too expensive for this purpose. I am merely showing the
approximate simple shape that could be employed.)
Its location, when placed, is essentially arbitrary. All cities, suburbs, and
towns, to say nothing of rural areas, are quite full of parks, fields, unbuilt
lots, golf courses, cemeteries, grassy medians, high-tension line
rights-of-way, gravel roads, beaches, and forested areas. Almost all of that
could be employed to hide a tiny pipe whose presence would probably go
unnoticed for years, and certainly for hours and days.
The main requirement to find the store is a precise GPS system, ideally one
which can employ WAAS (Wide Area Augmentation System), which usually will
provide a location accuracy of 1 meters. That alone would probably be
sufficient.
If people are assumed to only have access to ordinary GPS receivers, such as
those in smartphones, I have also suggested using a plastic molded
"corner-cube" retroreflection device to accurately send back light (or, with an
IR-only filter, IR) to the searcher. See Acrylite GP color 1146-0.
https://www.eplastics.com/plexiglass/acrylic-sheets/ir-transmitting This
material can be placed over an ordinary clear-plastic retroreflector, and
according to the graph shown it retroreflects only 1% of 1% (or 0.01%; it loses
99% on each pass through the sheet.) The retroreflection plane can be 'aimed'
in a specific direction, to make it even more unlikely to be accidentally found
by a random passer-by.
Another aid to finding such a cache would be to throw a few hundreds or
thousands of tiny (say, 1/100 inch diameter? polished glass beads, around the
target, after it was placed in a grassy area. These glass beads would,
themselves, be somewhat retroreflective, but could only be seen from above as
the searcher gets close to the cache. Or, a small retroreflection disk can be
placed, face-up, at or near the cache.
Jim Bell
