Why the scan radius is so small and why was PokeVision running better.
A lot changed since the days (lol) PokeVision was the leader in online tracking. First of all there was no API call check from Niantic at all. You could make 10 request second to their server from the same IP and same account without getting any kind of softban. Combine this with 1000 accounts and you could do 10000 requests/s. With only 1000 accounts. Server IPs weren't banned. Device weren't controlled. With a single call you could see pokemon 1kilometer afar. So with 10000 request/s you could actually scan the whole globe in probably 1-2h.
Then Niantic started fighting against all thrid party apps. They activated their signature check (Called UK6 because it was the sixth field of the request protobuf), it started limiting the number of accounts bound to one ip and it started limiting each account to be able to do one request once every 10seconds. Do the math. To be able to do the same amount of requests you could do in the first days of PokeVision, you would need a lot more IPs (and residential IPs), a lot more accounts, a lot more CPU (each request has to calcualte the UK6 which I was part of the reversing team of, fyi). They also limited the range of returned pokemon to 70m from the point of request. So to you the same amount of pokemon as previously, you would need to do about 20-30x more requests (and with the new limitation, calculate it again).
Yea so all these checks made it really hard for PokeVision to be able to function optimally, their AWS server IP got banned and they decided to shutdown.
Enters FastPokeMap, with a big precedent set by PokeVision were people unaware of Niantic checks thought it was easy to have the same performance than PokeVision. Let me tell you this, if PokeVision were to come back, they wouldn't have 1/100 of their performance they had at their peak because of all these new limitations. They would have to rewrite their whole engine/backend to accomodate with all the new restrictions put in place by Niantic.
I am working as a security researcher and I'm doing all this mostly alone on my own free time with a LOSS. I'm not making any profit. Donations and ads money aren't enough. I don't care. I want to please you guys to make sure you can enjoy the game again. And Niantic made it really hard for me to provide a stable service without spending a shitton of money. But you know what? Screw it. I'll do it anyway. Because the "customer" (or in this case the player) is always king.