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Targeting emergency alerts where they’re needed most

Targeting emergency alerts where they’re needed most

Whether it’s an approaching hurricane, a tsunami or an earthquake, timely warnings can save lives.  Unfortunately, if the warnings go too far afield they can spread panic and potentially create obstacles for first responders. Perhaps more problematic, warnings that are broadcast too broadly may not be taken seriously by those who are really at risk.

With the existing wireless emergency alerts (WEA), “there could be a lot of bleed over,” said Denis Gusty, Homeland Security and First Responders Group program manager at the Department of Homeland Security.

“That’s probably the worst-case scenario – a lot of people receive that message who should not receive it,” said Gusty. 

But now, with funding from DHS, researchers at the Johns Hopkins University Applied Physics Laboratory have developed a technology dubbed Arbitrary-Size Location-Aware Targeting (ASLAT), which is designed to ensure that only those who need to take action receive the warnings.

According to the research group’s final report, the main problem is that “the current WEA geotargeting mechanism has limited precision due to the relatively coarse granularity of cellular network sites.”  With the current system, emergency messages are sent to all devices within range of specified cell towers.

ASLAT, on the other hand, takes advantage of the location services in smartphones to direct messages only to those devices within specified polygons drawn by the originating agency.  Alerts are broadcast to an area larger than the target area, but when the mobile device receives the message, it compares its current location to the target area coded in the message before delivering the alert.

ASLAT takes advantage of three geolocation technologies in smartphones to determine location:  the global positioning system, mobile-device-based techniques that calculate radio signal travel times, and Wi-Fi proximity. According to the report, “these are all suitable for ASLAT because they provide adequate location precision, they do not introduce additional load on the cellular network and they maintain user privacy.”

Depending upon its location, the device will react in one of the following ways when a message is received:

  • If the device is unable to determine its location in a timely fashion, it errs on the side of caution and alerts the user by displaying the text information in the message.
  • If the device is inside the target area or if it is approaching the target area, it alerts the user by displaying the text information in the message.
  • If the device is outside the target area, but the user has indicated a relationship to the target area (such as a home or business address), the device warns the user by displaying the text information in the message.
  • If none of the above conditions is true, the device does not alert the user.

There are, however, drawbacks to ASLAT.  First, since the system requires communication between the sender and the receiving device, there may be delays in message delivery.  The research team dealt with this problem by allowing the sender to set a maximum delay, after which the device will receive the default WEA message.

More problematic, however, is the fact that, unlike existing WEA alerts, ASLAT depends on an application being installed on the end user’s device.

“For this to really work, everyone would have to download that application,” said Gusty.  Alternatively, manufacturers may be induced to install the app on phones, just as current smartphones have been WEA-enabled for reception of alerts.

Posted by Patrick Marshall on Aug 25, 2015 at 9:20 AM


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