# How to Use a Transit Level?

A transit level is a means of measuring, or surveying as it is also known, the location, elevation, degree of inclination of any object such as buildings, trees, fences relative to the placement of the transit. It is also used in cartography (map making) to create a detailed and accurate topographical (elevation) map. A transit is one of two parts needed to use this ancient tool (its use dates back to the ancient Egyptians). There is the transit which consists of a sighting glass (essentially a telescope) with markings much like a rifle scope upon a tripod which also includes a built in spirit (bubble) level. The other piece needed is a graduated rod which is usually marked in increments of inches and feet or in metric measurements. To use the transit, a site is selected and the tripod set up. The transit is then ‘leveled’ using the spirit level (this is critical for the measurements to be accurate for the sake of measuring horizontal level). The ground directly below the center point of the transit is considered ‘zero’ or base point, the height of the transit must be measured and remembered so that it can be used in figuring the elevation of the measured points. An assistant places the graduated rod upon the spot that is to be measured. The ‘surveyor’ looks through the transit and determines where on the graduated rod the cross hairs of the transit’s sight fall. The vertical difference between the base point and the transit is then subtracted from the reading and the result is the difference in elevation from the base point and the measured point. So, to give numbers to the example: base point is 0. Transit level is 50 inches or +50′. Placement of the graduated rod and measured height as seen through the transit is 64′. Subtracting the 50′ from the 64′ leaves a difference of 14′. The point of measurement relative to the base point is 14′ lower. Had the point of measurement been higher in elevation relative to the base point, the measurement less than the 50′ of height from base point to transit. I found the included article to be helpful and informative. For more information see here: