ABERDEEN PROVING GROUND, Md. (June 6, 2017) -- Army researchers are leveraging multiple technologies, including a tactical radio network and ranging techniques, to produce reliable positioning, navigation and timing, or PNT.
Both technologies fall under the broad Collaborative Navigation umbrella, which describes technologies that allow GPS-enabled Soldiers to share critical PNT data derived from surrounding assets to Soldiers who are temporarily without a signal.
"Soldiers have trouble acquiring GPS signals in a variety of situations, such as signal interference or after maneuvers when buildings, tunnels, or deep foliage block the signal," said Kevin Johnson, PNT engineer with the U.S. Army Materiel Command's Communications-Electronics Research, Development and Engineering Center, or CERDEC. "When the Soldier starts his or her receiver it may take up to several minutes to locate the GPS signal, based on where the space satellite is orbiting."
Moving seamlessly in and out of GPS coverage is critical for expeditionary mission command maneuvers, so acquiring a "fix," or usable satellite signal, must occur within seconds, Johnson said.
CERDEC is the Army's research and development lead for Soldier and ground platform PNT needs, and supports Direct Reporting Program Manager PNT.
"We're using our science and technology investments to develop complimentary PNT solutions that will address the challenges our Soldiers face in various tactical environments," said Chris Manning, acting director for CERDEC's Command Power and Integration Directorate, or CP&ID.
Network assistance is one aspect of Collaborative Navigation. It entails the GPS-enabled Soldier obtaining reliable data using a receiver, such as a Defense Advanced GPS Receiver, or DAGR, and transmit this information over the radio network to the disadvantaged Soldier's radio. The information seamlessly connects to that Soldier's GPS receiver to quickly allow access to the military GPS signal, provide a trusted location for the Soldier, and produce a picture of the battlefield assets.
"The GPS-denied or threatened Soldier obtains what is called a 'hot start' once he or she receives the satellite data so that he or she can immediately commence navigation," Johnson said. "Each Soldier acts as a sensor node capable of providing useful information to the network."
Ranging is another collaborative PNT concept, which can be used to establish position between nodes, or the distance between radios, and/or to share time.
"Timing is important to acquire GPS, synchronize networks, and even provide integrity if it is very precise," Johnson said.
"The ranging process commences when Soldier 'A' sends a signal with a certain time stamp to Soldier 'B,' who receives the signal with a new time stamp," said Nhut Vo, CERDEC PNT engineer. "That time difference determines how long it took the signal to travel and, when multiplied by the speed of light, will tell Soldier A how far he or she is relative to Soldier B."
Ranging does not necessarily provide absolute position; however, even establishing relative position can be a critical enabler to PNT.
"If a group of Soldiers aren't certain of their latitude or longitude, but they know they are within 'X' meters of the rest of their squad, they can still derive relative position, which is the distance with respect to your partner," said Eric Bickford, CERDEC PNT engineer. "This is valuable information because at least they know they have friendlies in the area to help avoid fratricide. This capability is especially beneficial in low visibility situations."
In a similar sense, a mounted PNT system can provide a dismounted Soldier system with information while riding within the vehicle en route to an incident.
"Once the Soldier disembarks the vehicle, his PNT system will be 'fresh and ready' to navigate without a need to perform a navigation system initialization, hence enabling operational tempo [OPTEMPO]," said Paul Olson, chief engineer for CERDEC's CP&ID Positioning, Navigation and Timing Division.
This technique will be demonstrated on a new program that CERDEC/CP&I will be kicking off this fall entitled "Dismounted Soldier PNT System Initialization," Olson said.
Collaborative PNT technologies not only improve situational awareness, they can also reduce the resources necessary for Soldiers to navigate. The Army cannot outfit every Soldier with top-of-the-line receivers, but PNT-enabling technologies allow for distribution of higher-end PNT technologies throughout the squad, either based on location or role.
Mounted, autonomous convoys could also benefit from collaborative navigation, both to aid PNT and to reduce resources. In an unmanned, leader/follower convoy, the front vehicle could be manned and equipped with the most robust, and costly, navigation sensors. Using a network, the Soldier could pass PNT information back to the unmanned vehicles in the convoy, which are equipped with less expensive equipment.
"In this scenario, the followers would have about the same level of situational awareness as the front vehicle to successfully navigate," Bickford said.
When GPS interference leaves Soldiers without the safety net of PNT, collaborative navigation information sharing provides situational awareness not possible with a standalone system on one person.
"The battlefield is not filled with the infrastructure civilians have, like cell towers and iPhones with 4G capabilities," Johnson said. "Collaborative navigation is an effective method to get critical information to Soldiers whose missions, and safety, depend on accurate PNT."