Network aided positioning solution in urban and other weak GPS signal environments

The GPS signals can be significantly attenuated, or even blocked, when they have to be received inside buildings, under foliage, in jamming, etc. The NAVSYS solution to this problem is to use network aiding with our POSCOMM, Position/Location Tracking and Communications Software Defined Radio (SDR).

The network aiding function requires the use of multiple “master” units to be operating in the network in locations where they have access to the GPS signals. These can be either other participants in the operation or pre-positioned “nodes” to provide coverage in areas where GPS has difficulty operating. These master units transmit a Time of Arrival (TOA) message which includes a pseudo-random sequence from which the time of arrival at the “slave” unit can be precisely determined. A message is also sent including the precise time of transmission of the TOA message and the precise location of the master unit based on the GPS observations. The TOA differenced with the time-of-transmission provides the slave unit with a pseudorange observation from each of the master unit’s locations. This can be used to solve for the position of the slave either using the TOA updates alone or using a combination of both the GPS and TOA observations.

Embeds easily into existing or sourced sensors

Because the GI-Eye system is a software platform it can be integrated to run on existing GPS, inertial, and visual sensors, reducing size and weight for your application. NAVSYS can also provide numerous sensors to meet the performance requirements of your application. Because of its modular design, it enables sensor upgrades over time with only software configuration changes.

Advantages

The POSCOMM SDR approach has the following advantages:

• Provides a low cost hardware implementation including both GPS and communication functions in a single device.
• Allows for power saving for man-portable operations through sharing of common components and through snapshot tracking (GPS DFE is only powered on when data is being collected).
• Improves the GPS signal tracking capability by providing network assistance through the communication link to allow operation under low signal power conditions.
• Improves GPS positioning performance by providing GPS corrections through the network.
• Provides a back-up positioning capability using network aiding with TOA observations in the event of GPS signal drop-out.
• Allows one-way TOA messaging to be used which significantly reduces the loading on the communications network.