RealMotion™ for Public Health FAQ: Contact Tracing Using Geolocation

By 七月 9, 2020Resources

Q: What is the RealMotion Effectiveness as compared to conventional contact tracking?

Contact tracing is an essential component of the toolbox for containing the COVID-19 disease outbreak. Contact tracing is the process of identification of persons who may have come into contact with an infected person. Conventional contact tracing herein is referred to as by interviewing the infected contacts and chaining it up to figure out the potentially infected people. Conventional contact tracing by Partners in Health is always necessary. Geolocation is just a tool they may use to fill gaps, discover discrepancies, and improve efficiency:

1. Fill gaps:

There are occasions where the patient is in a coma, already deceased, or has forgotten exactly where & when s\he went to. When the patient is in a coma or already deceased, geolocation becomes the best way to do contact tracing. With geolocation, contact tracers can identify people exposed to the patient and quarantine them to assist in containing an outbreak before it could happen.

If the patients are alive and well, results from geolocation can help the patients to quickly recall exactly where and when they went to and who they may have come in contact. The description could improve from, “I went to that shop last Wednesday” to “I went to that shop at 9:30 and left by 10:00 last Wednesday. I took the ABC road by cab.” Moreover, in this context, geo-location can also tip-off which people were in the shop from 9:30 to 10:00, which an infected person would not normally recall; due to the unknown faces.

2. Discover discrepancies:

There are circumstances that people are not truthful or remember correctly. In some countries, outbreaks were due to people lying or attempting to hide specific locations they have visited before. This has been difficult, if not impossible, to track the virus and put the public at risk to get infected with COVID-19. In some cases, contact tracers initially believed what was reported by patients but turned out to contain some discrepancies, which prompted the contact trackers to conduct more comprehensive interviews. 

3. Improve efficiency:

It is much easier, faster, and more time-efficient for contact tracers to work when they have the right tools to perform source and contact tracing. Furthermore, geolocation has applications beyond contact tracing; such as alarming if a quarantined individual leaves the quarantined area (either home or hospital), or authorities need to do crowd management due to the clustering of a large group of people during a lockdown. All these applications can significantly aid in improving efficiency.

More actions can be taken accordingly, such as sending alarm SMS to everyone who was in the proximity so that they can be aware of self-quarantine if they were indeed at the locations confirmed by the patients.

Q: What is the RealMotion Accuracy of contact tracing?

Contact tracing with geolocation helps to provide IMSIs/MSISDNs which are likely in proximity to the Infected person/IMSI. It cannot absolutely confirm the contact but can provide the list of potentially exposed people.

The interview done by the authority or public health professionals takes precedence over the auto-generated list because there are too many factors affecting cell phone transmission signals and signal fluctuation. With a good geolocation system, the error deviation becomes less, approximately about 50 meters (downtown areas) to hundreds of meters (suburban areas) median error, provided that it is not GPS accuracy. Additionally, the system can further utilize the Minimization of Drive Test (MDT) to provide an accuracy of 10 to 50 meters utilizing the GPS coordinates reported in the MDT enabled measurement reports, especially for the outdoor environment. However, GPS accuracy fails in the indoor scenario, where a geo-location can supplement such weakness and cover all the subscribers, and provide samples.

Q: What is the RealMotion Accuracy of geo-fencing?

Typically, COVID-19 related analyses or geo-fencing are performed by comparing relative locations instead of absolute locations. For example, the algorithm identifies the cluster of calculated positions which is most likely to be the user’s quarantine area. Due to reflection and even multipath, the positioning is often shifted from the actual physical location, but ideally the shift is in the same direction majority of the time. For example, positioning could identify my quarantine location as a hundred meters west of the actual address.  If every time the position is west of the actual address, the geo-fencing system will just need to compare my latest positioning result to this cluster. If I am within the cluster, even though I am a hundred meters west of the latitude longitude of my quarantine area, I am staying tuned. Only if I move out from the cluster, I am violating the quarantine.

The reason to use a cluster instead of one single location is that there is RF signal fluctuation. Even when someone is not moving at all, the RF signal fluctuates, as can be clearly seen on cell phones in engineering mode. Therefore, the raw positioning result jumps around according to signal fluctuation; especially when there are less than 3 reference sites or there is not enough measurement report. Our algorithm describes this cluster with a (latitude, longitude) and a radius, so that other applications can use this to calculate if a user is likely to be away from the quarantine area.

Q: What are other digital Contact Tracing technologies?

Geo-Location comparison with other technologies

Feature Description RealMotion™ Bluetooth Application Crowdsourcing Application
Tracking Utilizes cellular data to geo-locate users Utilizes Bluetooth beacon to track the person in a Peer-to-Peer fashion Requires users to send the data to the application server
Support All the users on the network are supported Only support users with the application installed but requires 60%+ population to install to be effective. Only support users with the application installed but requires 60%+ population to install to be effective.
Source and Contact tracing Supports nation-wide, provides a global view to the health authority. Works in peer-to-peer fashion, indicates a user if s/he is in close proximity of a COVID-19 Patient Depends on the crowd-sourcing data. If an infected person does not install the application, it has the potential to victimize his neighborhood.
Quarantine Support Support quarantine violation 24×7 Does not support Does not support
Crowd gathering/Crowd management Supports to detect places with huge gatherings Only identifies people within very close proximity (10 – 50m on average) Supports to detect the gatherings, also depend on the installation in a given network
Location analysis Provide the whereabouts of the infected user to authorized health professionals. Only alarms the presence of a nearby infected person, without providing the location. Protects privacy completely. Supports location of the whereabouts of the infected user; highly dependent on the application usage. Protects privacy completely.
Network-wide view Supports network-wide view Does not support Depends on the installation numbers.
Subscriber density Supports network-wide subscriber’s density Does not support Depends on the installation numbers.
Curfew Supports curfew violation (imposed by the government) Does not support Does not support

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