In the late 19th century, surveyors created topographic maps in the field. A series of points were measured in the field using tape and compass traverses with elevations determined with an aneroid barometer, and used in a process known as field sketching to draw a terrain representation using contours. read more
First, measure some special points like elevation points to mark the height. Second, based on points draw lines like contours. Third, interpolate by some methods to simulate the surface. read more