The Calgary Parking Authority (CPA) in Calgary, Alberta, Canada manages one of the most advanced automated parking systems in North America. First implemented almost seven years ago, the web-enabled ParkPlus system makes it easy for customers to pay for parking with pay machines or by cell phone while a GPS-enabled digital chalking and License Plate Recognition (LPR) system helps parking enforcement officers quickly and accurately detect parking non-payment violations.

In recent years, Calgary has emerged as one of Canada's corporate headquarters with a growing economy that thrives on oil and gas, tourism and high tech manufacturing. Economic and population growth has facilitated the construction of an increasing number of high rise steel and glass buildings along Calgary's narrow streets.

Unfortunately, increased multipath errors during parking zone checks diminished the parking enforcement system's reliability and efficiency.

The tight urban corridors can throw GPS positions off by 500-600 metres or more, creating considerable work for enforcement officers charged with reviewing each potential parking violation for positional accuracy.

Looking for a way to improve data accuracy and save time and money, the CPA agreed to test a NovAtel® SPAN® Global Navigation Satellite System (GNSS) plus Inertial Navigation System (INS) solutions on one of its city parking enforcement vehicles. The improvement in positional accuracy was so impressive that within three months, the CPA had installed the SPAN system on all of its city-based parking enforcement vehicles-and cut multipath errors to 1% saving considerable time, money and boosting morale throughout the agency.

Positional Parameters

The CPA is charged with implementing the City of Calgary's parking policies. The agency manages on- and off-street public parking facilities and enforcement programs and provides parking advisory services. Calgary has about 6,000 on street spaces located in about 800 zones, along with 7,000 off street spaces in surface lots and parking garages.

In 2007, the CPA replaced all of its parking metres with the ParkPlus system, which allows payment via on-site pay machines or by a registered ParkPlus cell phone account.

Parking enforcement officers use Tannery Creek Systems' autoChalk® digital chalking and LPR system to monitor parking zones throughout the city. The fully automated heads up system is comprised of four cameras, a rugged laptop, two lasers, and a GNSS receiver to determine accurate time and position of observed vehicles. The autoChalk system scans up to two cars per second, at 40 km/h, on either side of the road and takes profile and license plate photos of each parked vehicle. Each autoChalk system daily scans and processes about 2000 vehicles parked on Calgary roads. Calgary has six autoChalk units.

ParkPlus uses the license plate to associate paid parking sessions with a vehicle, hence parked vehicles' license plates are automatically checked to see if they have a paid parking session. Every license plate image with an unregistered payment transaction is reviewed by enforcement officers to verify if there is a parking violation.

Miles Dyck, manager of Parking Enforcement for the CPA, explains, “The electronic system is not 100% accurate, so our officers must look at each unregistered plate to see if there's an error. For instance, maybe the camera reads the letter D as an O or 0. We also, don't issue tickets for vehicles that are actively loading or unloading, so those instances must be manually removed from the system.” All citations are reviewed by a parking enforcement officer before issuing.

Dyck added that the lengthiness of the manual review was compounded by the GPS errors.

“In an urban environment like Calgary with tall structures, our GPS-enabled system could incorrectly locate parked vehicles by hundreds of meters,” he says. “We weren't getting the correct GPS locations for 6-7% of the vehicles-that's about 1,400 vehicles every day that we would have enforcement officers manually review and place in the appropriate parking zones. Our officers were spending 4-5 hours every day reviewing potential parking non-payment violations.”

SPAN Accuracy

To correct the problem, Tannery Creek Systems, developer of the autoChalk solution, recommended that the CPA add the NovAtel SPAN technology GNSS+INS navigation system to the digital chalking and LPR system as a way to minimize the potential for multipath errors.

SPAN combines a GNSS with an Integrated Inertial Measurement Unit (IMU) to bridge GNSS outages for more reliable positioning in challenging environments such as urban canyons. The SPAN-enabled GNSS performance with integrated inertial measurements allows for faster signal reacquisition and faster return to a fixed integer carrier phase solution after signal outage. For Bill Franklin, president of Tannery Creek Systems, the practical user benefits are substantial. He says, “The Novatel SPAN GPS provides amazing accuracy even in harsh deep urban canyons with brutal multipath conditions. We typically see real time accuracy well less than 20 metres even in the toughest of conditions. It's amazing technology.”

In a different project Tannery Creek used post processing, performed by NovAtel's Waypoint Inertial Explorer ® package, to more accurately position vehicles in brutal downtown urban canyons. But the real time accuracy led Tannery to recommend the SPAN solution for use in Calgary.

Franklin commented, “We had tested the SPAN system in another city and were impressed with accuracy even before post-processing. We believed the addition of the SPAN system could map 98% of a city such as Calgary with greater accuracy and better results, namely fewer multipath errors, thus a greater number of vehicles properly located during parking enforcement checks-and therefore less time spent staring at a screen.”

The CPA agreed to test the SPAN system on one of its parking enforcement vehicles in early 2013.

Dyck recalls, “The difference was immediately visible. After piloting the system for several weeks, we were able to cut our unregistered plates from 7% to about 1%.”

Easy Implementation

Three months after installing the SPAN system on the first parking enforcement vehicle, the CPA purchased three more SPAN solutions to be installed on the remaining three city-based parking enforcement vehicles. In one day, parking enforcement officers captured almost 10,000 parked vehicles. Out of those 10,000, fewer than 300 vehicle positions were dropped or mislocated.

The addition of the SPAN system has had unexpected benefits to the CPA in the way the parking enforcement training program is implemented. In the past, parking enforcement officers have had to have considerable familiarity about the downtown area in order to properly post-process the parking data and assess the vehicle locations, especially given the previous multipath error issues.

Dyck says, “With the new system, our parking enforcement officers don't have to have prior knowledge of downtown. Training is minimized. In fact, we've been able to cut training from one month to two weeks or less.”

Much of the training is now focused on system operation and calibration, which must happen at the beginning of every shift, and requires from 5-10 minutes to ensure positional accuracy.


For the CPA, a large part of its Return On Investment (ROI) will come from the time saved by parking enforcement officers who manually review and place vehicles in the appropriate parking zones.

Prior to the SPAN system, the officers spent 4-5 hours per day reviewing images to determine the correct GNSS locations. As many as 1,400 parked vehicles were mislocated due to multipath errors on any given day. Now the number of mislocated vehicles is down to a few hundred-and the time spent reviewing and positioning the parked vehicles that are mislocated is down to 1-2 hours instead of 4-5 hours.

CPA estimates the ROI for the SPAN systems will be less than two years.

Dyck says, “Besides the time savings, the improvement in accuracy has been a great morale booster for our agency. Hours and hours looking at a screen to verify vehicle locations is tedious work. With that time savings, I've been able to reposition one full time parking enforcement officer to other tasks.”

Management Efficiency

An unexpected benefit of the SPAN solution for the CPA has been increased revenue. Dyck adds, “We return all of our net revenue to the city. The more efficiently we are able to enforce parking regulations, the more revenue we return to the city, which is ultimately used to build or repair infrastructure.”

Also, while the community is not aware of the technology that the CPA has implemented, they might be aware of the increased accuracy of the data collected, which contributes to an overall rise in the CPA's overall enforcement system credibility.

Dyck says that he's seeing fewer court appeals and fewer hassles for individuals questioning parking tickets. “When the SPAN-enabled system takes a picture of a car, 99% of the time that car is in that zone,” he says. “This is particularly important when tickets are appealed at court. When presented with accurate GPS referenced location and photo evidence, we get more guilty pleas, and the Court itself has an increased assurance that the technology that produced the tickets is legitimate.”

The CPA's goal is not to ticket people parking in the city but to encourage higher compliance. Internal operational goals are to minimize time spent per citation including manually reviewing vehicle images for those vehicles that can't be placed.

“We try to make parking as convenient and easy as possible,” concludes Dyck. “The latest technologies help us do that with improved efficiency and accuracy of data. In an urban corridor such as Calgary, the SPAN technology certainly delivers a more efficient, accurate solution.”