Geohash my positions
Python 3, 250 bytes

lambda b,a:(lambda l:&quot;&quot;.join(&quot;0123456789bcdefghjkmnpqrstuvwxyz&quot;[int(&quot;&quot;.join(map(str,l[i*5:][:5])),2)]for i in range(8)))(sum(zip(f(a,180,-180),f(b,90,-90)),()))
f=lambda a,u,l,p=20:p and([1]+f(a,u,(u+l)/2,p-1)if u+l&lt;a*2else[0]+f(a,(u+l)/2,l,p-1))or[]

Try it online!
I think using named functions would probably be better... anyway. I don't have time to golf this further yet, so just posting it here first.