Q4:
I guess for any base other than 2^n (n integer), the numbers will be 'smoothly' spread out over the digits. For bases 2^n, doubling (powers of 2) is nothing but doubling the first digit, which results in lots of zeros at the end.
Q5:
Depending on the location:
if it is a city, you want to see the entire city with some padding.
If it is a road, you want to see the entire road.
If it is a crossing, you want to see both roads,
Same holds for states, counties, countries, continents.
Giving a GPS coordinate is much more subtle though. You probably want to find the nearest n-cities/rivers, and compute the maximum distance for that. If that exceeds the size of the country, just zoom to the country.
If the point is on water (oceans), you probably want to zoom as to see the containing ocean entirely...
