Areas of equal elevation are connected by lines on a topographic map.

meridian

longitude

contour

latitude

Contour

Explanation:

These are just lines that follow the points on the map that contain the same elevation, and are not the lines that one sees drawn for finding particular locations on a projected flat surface of the Earth like meridians or parallels, that give us longitude and latitude of a place.

The topographic lines are actually trying to represent (give an image of) the third dimension (elevation) in a two dimensional chart.

force required to detach it is given by

charges are taken to be fundamental charge

now we have

so above is the minimum distance at which it will detach