Taking GPS Indoors!
subATTO™ acquires to -155dBm and tracks to -157dBm
subATTO™ is the cornerstone “Deep Science” fabric upon which SigNav’s products are engineered. This unique, proprietary (patented), seamless multi-mode high sensitivity technology incorporates both Assisted and autonomous GPS, providing compelling solution for a broad range of applications. Precise GPS timing and positioning can now be provided in “difficult” environments, such as indoors, in urban canyons and under dense, wet tree canopies yielding a practically go anywhere solution, extending GPS’s use into previously untapped applications and locations.
subATTO™ refers to the technology’s ability to acquire and then track GPS signals weaker than an attowatt, or 1x10-18 Watts (-180dBW) or -150dBm. Operation at this level and below is essential to provide reliable operation in difficult environments.
subATTO™ outperforms other A-GPS schemes by:
- Supporting full navigational capabilities rather than just isolated position fixes
- Incorporating Advanced Ambiguity Resolution it can start-up in exclusively weak signal environments eliminating the need for complex initialisation procedures such as pre-programming or exposure to strong GPS signals.
- Low power consumption through continuous tracking rather than repeated acquisition making it ideal for handheld devices
- Requiring minimal assistance data for acquisition and ambiguity resolution, reducing backchannel bandwidth requirements and associated costs
- Shorter integration periods enabling fast acquisition whilst minimising the use of correlators for any given sensitivity, reducing hardware complexity and cost
Signal strengths in typical environments
Strong: -121dBm to -142dBm
Autonomous GPS operates in strong signal strength environments where receivers are said to have a “clear views of the satellites”. Under these conditions there are no obstructions in direct line of sight from the GPS antenna to the satelitesand there are no reflected or multipath satelite signals present. Examples of such environments include deserts, oceans, open fields and low noise residential areas.Weak: -142dBm to -150dBm
Assisted GPS operates at weak signal strenghts where the signal is too noisy to extract the navigational data. Examples of such environments include forests under dense wet folliage and various indoor environments near windows.Very Weak: -150dBm to -160dBm
Below -150dBm is truly subATTO™ territory. Here receivers detect very weak reflected and multipath signals. Examples of such environments can be found within office buildings and multi-storey car parks in sight of outside windows and doors.SigNav’s Assistance Network
To aid developers, SigNav has deployed an Assistance Network, consisting of redundant servers and gatherers placed strategically around the world to collect satellite ephemeris. Accessed over the internet, updates can be automatically downloaded to subATTO™ powered receivers under test, dramatically contracting development cycles.