The ruler allows you to measure distance between any two points on the virtual globe. You can select the ruler option from the tools menu. You can then simply select the required points to measure the distance between two points. You can also search for the places using the search panel and mark points at the required places. In the line tab you will be able to see the ground distance and the angle between the two points. If on the other hand you go to the path tab you will be able to select multiple points to measure the distance on the ground. You set the units of measurement in the line tab from the drop down menu next to the map distance.