lines are close means steep grade. if the line makes a circle that is the top of a mountian or hill. if the lines make a V that is the buttom of a ravine and will usually have a creek running at the V. if the lines are far apart it will be flatter. usually there will be set lines marked with a number. this is the altitude, find another line up or down from this line and find another altitude. deduct the two and that is the distance in feet they two are seperated by. use the legend to see how far, usually in miles, those two lines are and you know how many feet in elevation you will go up a hill walking X number of miles.