The center of the intersection of Market St. and N 15th St in Philadelphia
is located at
39.9525° North latitude
75.1653° West longitude.
Other places around the city all have somewhat different coordinates.
Forget about 'lines' of latitude and longitude. There's no such thing as a
standard set of lines, with no latitudes or longitudes between the lines
and you have to pick lines that are close to the place you're interested in.
Just like on a ruler . . . there are only some marks on it, at some lengths,
but that doesn't mean that no lengths exist between the marks. You
would not ask "What mark on the ruler is your height ?". You would
ask "How tall are you ?", and I could tell you any number that's correct,
even if there's no mark on the ruler right there.
