You will most likely get everyone who’s phone was within the overall geofence +100yards or so (sometimes better sometimes worse, really depends on what and how you are measuring).
That will include everyone above and below you with good enough signal to get through. Hospitals are usually tall in urban centers, so 5-10 stories of people?
Now you have your potential list. However, the real segment you just made are hospital visitors + employees/vendors.
Maybe you can exclude those that you see a lot or on a regular cycle as staff/vendors.
You are still not very close to just “personal injury” data.
Usually, you’ll need to combine this with something more to make better segment overall and go from there.
Unfortunately, data vendors will often market the above without much cleaning as “ER visitors” or “people with health problem X”.
There are numerous threads on HN about how bad some of these segments are - people tagged with mutually exclusive segments, wrong info, etc. That’s why FB and Google, and to a lesser extent for now Amazon, are sitting on some really valuable data - we tend to tell them explicitly and/or they have fine-grained location on us.
And let’s not forget that stuff like this has spurred responses like GDPR.
(I'm equal parts horrified and impressed that someone's actually doing this... This is why, as much as it's annoying at work, I really like the GDPR...)
I’d consider using something like this if I had already deployed marketing capital elsewhere and hit diminishing returns. These are more akin to gambling in my book.
Not to say that polygon-based geofencing doesn’t work. It does, but with larger, less dense locations where the lower fidelity is good enough.
I'm not so sure in this specific case. If I were a (cue pejorative stereotype for emphasis) scumbag ambulance chasing lawyer - I doubt there's anything in Facebook or Google's ad targeting demographics that'd give me quite the same opportunities as a rough-and-ready demographic of "people at or close to hospital emergency departments" to try selling to...
I hope (but am prepared to be shown otherwise) than neither Facebook nor Google have an easy way to target ads to people who've just posted "Faaark! Just been in a car accident! #YOLO #GladIBoughtAVolvo #ShouldntHaveBeenTexting"
(Evil-idea: I wonder if anyone's using siome combinations of accelerometer and GPS data to detect potentially traumatic events and selling that data on?)
This is somewhat true of my local hospital, but the ER facility is dwarfed by the number of non-ER facilities in a 100-200 yard radius. I personally see two specialists in the facility, receive diagnostic imaging and bloodwork, plus physical therapy within that same area. I additionally drive every day through that radius as I live on the same street as my hospital.
I dont want or need these sorts of ads cropping up.
The large local hospital in Redmond WA (Evergreen) is right next to a strip mall and shares a parking lot with a movie theater.
In an urban setting, sure, but most hospitals I've been to are MASSIVE, sprawling facilities.
Seems like the parking lot is close enough to being in the ER anyway.
Regardless, the 'waste' will be more from targeting health care workers, janitors, visitors, etc, but the targeting will still be more effective than not doing it at all.