Secure, reliable access to GPS has become a crucial part of warfare, with military forces like the Canadian Army relying on its accuracy in a variety of situations, including firing GPS-guided munitions from their weapon systems.

These munitions produce corrections that allow them to be guided with much more precision than a
ballistic-only shell, said Peter Soar, NovAtel’s Business Development Manager for Military & Defence. They are one of the many ammunition natures that can be fired by the Canadian Army’s M777C1 Howitzers to provide close fire support without sacrificing range, stability, accuracy or durability. The M777C1 is equipped with the Digital Gun Management System (an inertial navigation unit with an embedded GPS receiver) that enables the crew to bring the gun into action quickly and to engage targets precisely, particularly when employing precision-guided munitions.

While GPS offers many advantages during combat, including precision positioning that can be used to diminish collateral damage and to reduce the number of shots needed per mission, using this technology doesn’t come without its challenges.

“GPS signals are weak and vulnerable to interference, both accidental and intentional, making it critical to protect the GPS receivers from jamming that could lead to solution denial,” Soar said.

In the case of GPS-aided munitions, it is necessary to provide the shell’s GPS receiver with data about the GPS constellation before firing. This enables the receiver to acquire the GPS satellite signals within seconds of being fired. So although artillery guns like the M777C1 can be operated in conventional modes without GPS (using optical sighting techniques), when using GPS-aided ammunition it is essential to have a reliable GPS signal available at the gun.

GAJT 710ML NovAtel logo

NovAtel’s GAJT antenna offers a solution that helps ensure signal reliability. GAJT antenna systems protect against GPS interference by dynamically adjusting the antenna gain pattern and steering “nulls” toward the directions of interferers so bad signals are not amplified and good GPS signals still get through. This prevents interfering power from entering the GPS receivers, allowing them to acquire and track the satellite signals they need to function properly.

The Canadian Army trialed the GAJT-AE-N, the smaller of two GAJT form factors, late last year in live-firing conditions on the M777C1 Howitzer.

“The Army purchased the Howitzer for operations in Afghanistan,” Soar said. “It’s a versatile gun that can fire the heavy 155 mm ammunition while being tactically mobile. But for it to be most effective when using GPS-guided ammunition, it must have access to reliable GPS without the risk of falling victim to jammers.”

The trial was conducted at Canadian Forces Base Shilo in Manitoba with the support of the Build in Canada Innovation Program
(BCIP) of Public Services and Procurement Canada. The BCIP procures and tests latestage innovative goods and services within the Federal Government to help Canadian companies go to market.

This was the second time the Canadian Army tested GAJT technology with the support of BCIP. The first test, completed in 2014, evaluated the performance and usability of GAJT-700ML, the prototype that led to the operationally-fielded GAJT-710ML. GAJT proved its anti-jamming capability worked during that trial; the second test was designed to show that GAJT units could remain operational during live firing.

The most recent test demonstrated the technology’s robustness. The units remained intact even when exposed to the powerful shockwaves and vibration produced every time the weapon fired. The test was a “snapshot;” more qualification tests would be needed to field GAJT in this application. However, this excellent step, facilitated by the Government of Canada, helps NovAtel bring GAJT-AE-N to this market.

“I am proud to support Canadian companies via the Build in Canada Innovation Program, as administered by Public Services and Procurement Canada. Through our independent testing, we saw that NovAtel’s GAJT-AE-N continued to work under the most demanding circumstances,” GAJT Trial Director Captain Thomas Booth, CD said, “indicating it could potentially be employed to preserve a combat force’s freedom of action in a hostile and unforgiving environment.”

The detailed trials report, produced by the Canadian Army, will assist NovAtel in marketing GAJT to Allies.

The Canadian Army purchased five of the GAJT-AE-N units with Controlled Reception Pattern Antennas (CRPAs) to test on the Howitzer. The GAJT-AE-N, designed for smaller platforms with more integrated requirements, uses a four-element CRPA and can null simultaneously in three directions on both GPS L1 and L2 frequencies.

GAJT 6For the trial, the team mounted two GAJT-AE-N units on the gun. The first was hard mounted in an experimental housing designed by the Canadian Army, and placed so it would experience the maximum shock and vibration. The second was shock mounted underneath the carriage in the belly pan that contains the sensitive communications and computation equipment. A third GAJT-AE-N was placed on the ground under the muzzle to experience the effect of the overpressure when the gun was fired. The M777C1 used was from “A” Battery, 1st Regiment Royal Canadian Horse Artillery.

“The aim was to assess mechanical and functional survivability,” Soar said. “They were firing at the maximum charge. All three of the GAJTs survived, continued tracking during the fire missions and were in perfect working order after 25 rounds. Basically, we had 100 percent success on the trial. We are grateful to the Canadian Army for their assistance, especially the trials team and to the Officers and Soldiers of “A” Battery Royal Canadian Horse Artillery who were helpful and tolerant, as well as interested in the capability that GAJT could deliver to the Army.”

GAJT is designed to work with any GPS receiver, either civilian or military, so there was no need to replace the GPS receivers already installed before testing. The Defense Advanced GPS Receiver (DAGR) is typically used in military operations, as was the case for these trials. GAJT has been tested many times with DAGR and is easy to integrate. 

The GAJT BCIP trials are now complete, and NovAtel is marketing GAJT-AE-N as well as supporting users who have already integrated the technology into Unmanned Aircraft Systems (UAS) for operations where GPS jamming is an issue.

Participation in the trial does not mean the Canadian Army intends to purchase and field GAJT, but if a requirement does emerge, NovAtel would certainly offer GAJT. The Canadian Army also has benefitted from the trial and has a better understanding of what this type of anti-jamming technology can mean for future operations. The trial demonstrated how GAJT can benefit the military and has generated interest from systems integrators in Canada and among Allies.

The First Test

The Canadian Army, also with the support of BCIP, first tested NovAtel’s GAJT antijamming capability in 2014. In that case, the GAJT-700ML was tested on a Light Armoured Vehicle III Observation Post Vehicle (LAV III OPV) of the Royal Canadian Horse Artillery in operational conditions. The product that emerged from that development is the GAJT-710ML. It has seven antenna elements, so it can make nulls in six directions, and is in a form and size that fits standard armoured or light vehicles Everything fits in one box that is designed for easy retrofitting.

The LAV III OPV was chosen for the trial based on its needs for precise Position, Navigation and Timing (PNT) in its role of target acquisition for Artillery, other Indirect Fires and for Close Air Support. GAJT protected the vehicle’s PNT systems during the trial, even during GPS jamming. The equipment operated on the same level of precision and functionality with GAJT as it
does with the standard GPS antenna.

“The Canadian Army requires accurate, secure and reliable access to Global Positioning Systems to conduct operations throughout the full spectrum of conf lict in all potential theatres of operation,” Colonel Andrew Jayne, Director Land Requirements, said in 2014. “With the ever-increasing demands on the electromagnetic spectrum and threat of
harmful interference, technologies which contribute to the assurance of position and timing information are a critical enabler of Army and Canadian Armed Forces operations in today and tomorrow’s operating environment.”

There’s nothing that gives more accurate, precise position with worldwide coverage than GPS, which is why it has become so common in military operations. But no matter the situation, military personnel need to know their GPS will deliver precise PNT—even when the enemy attempts to jam the satellite signal or the signal experiences unintentional interference.

GAJT 5“The military says there are three levels that describe the assurance of position, navigation and timing,” Soar said. “First is the ability to access PNT, next is protecting PNT, and finally there is the need to be able to trust PNT. Access is a done deal, particularly if an encrypted military receiver is being used. Protection is a work in progress, and that’s where anti-jam systems like GAJT and multi-sensor navigation like NovAtel’s SPAN® GPS+Inertial system come in. Trust is also a work in progress, though there’s a lot being done in that area as well.”
GAJT is an important technology for this
Army and others who have concerns about
GPS jamming.

“Some say the best way to overcome GPS jamming is to not use GPS, but that’s just not possible or sensible at the moment, so they need to take protective steps toward Assured PNT,” he said. “After these successful trials, they now know solutions are available to them.”