A-GPS explained in historical context

A-GPS explained in historical context
http://www.gps-practice-and-fun.com/a-gps.html

What makes Assisted-GPS work so well

is that the wireless network, using its own GPS receivers, as well as an
estimate of the handset’s location down to cell/sector, can predict with
great accuracy the GPS signal the handset will receive and send that
information to the handset. With this assistance the size of the search
space is greatly reduced and the time-to-first-fix (TTFF) shortened from
minutes to seconds. In addition, an A-GPS receiver in the handset can
detect and demodulate signals that are order of magnitude weaker than
those required by conventional GPS receivers.

An example is SnapTrack’s hybrid A-GPS location solution, which takes
advantage of the complementary nature of both network and GPS solutions
by using both cellular/wireless network information and the
satellite-based GPS information to directly improve the positioning
availability, sensitivity, accuracy and time-to-fix. By combining the
two information sources, SnapTrack’s hybrid solution can provide a
position fix with as few as one satellite and one cell site.
SnapTrack’s multimode technology offers additional functionality to the
basic Assisted-GPS (A-GPS) architecture. The multimode system can work
without assistance from the wireless network. In this mode, it operates
similar to conventional GPS but with dramatically increased sensitivity.

SnapTrack’s SmartServer Hybrid Wireless Assisted GPS (A-GPS) solution
offers an average of 15dBm of additional receiver sensitivity, and
20-30dBm in hybrid CDMA-based configurations. (We have no affiliation
with SnapTrack).

See: http://www.gps-practice-and-fun.com/a-gps.html

On 4/6/11 7:50 PM, Sam Wormley wrote:

On 4/6/11 7:50 PM, Sam Wormley wrote:

I just did a quick test of an GPS altimeter app on my iPhone 4.

Accurate Altitude reading by 10 seconds after "cold" start.

Indication of full compliment of satellites by 20 seconds after
cold start.

Another GPS app estimates the horizontal error ±16 ft and vertical
error ±31 ft

The Apple native maps app places your location (and heading) on
google maps. Another app (Topo Maps) shows location and heading
on USGS Topo Map that automatically download as needed. No costs
other than the app itself.

My Air Nav Pro app works much like the hand-held GPS receivers of
the early 90s.
o Destination Waypoint
o BRG
o Distance
o ETE
o ETA
o Groundspeed
o TRK
o ALT
o Flown Distance
o Estimated Horizontal Accuracy
o Estimated Vertical Accuracy
o Longitude
o Latitude
o Statewide Background Maps
o Other mapping available