In 1914 and 1915, the
Forestry Quarterly published a series of articles on the use of the Abney level. These tutorial articles remain useful today, but the primary reference for usage is the 1927
Abney Level Handbook. The Abney level is typically used at the eye height of the
surveyor, either hand-held or mounted on a staff at that height. To measure lines on a particular slope, the desired angle or grade is first set on the level and then the surveyor sights through the sighting tube and brings the cross-hair in line with the bubble in the level while viewing the target. This allows the surveyor to see if the target is above or below the line of sight. To measure an unknown slope, the surveyor first sights a target along that slope and then adjusts the angle of the level until the bubble is centered on the cross-hair. Once this is done, the slope may be read from the scale. Because the level is typically held at the surveyor's eye-height, it is common to use the face of a second surveyor of similar height as a target. If the second surveyor is not the same height, the approximate location of eye-height must be noted (i.e. chin, nose, top of head). Mounting a face-sized target at eye-height on a
level staff may be more accurate. Because most Abney levels do not contain a telescope, direct reading from a level staff is only possible at short range, although it is possible to make special staffs that can be read at a distance without magnification. ==Common uses==