How to Use an Abney
To determine the elevation difference between you and a specific point Point the sight at the selected point for which you wish to know the elevation difference and view the location through the sight. Holding the Abney steady read the angle difference from vertical off the side. Next measure the ground distance from you to the selected point using paces or a measuring tape. To calculate the vertical elevation change use Equation 1.
See the measuring of elevation with an Abney Level HERE
See the measuring of elevation over the course of a survey HERE
To determine multiple locations with the same elevation Point the sight at a point with a determined elevation, noting the angle difference from the vertical. Move the Abney in any direction that does not change the angle measurement on the side of the Abney level. Record all significant locations seen through the sight. These are all landmarks with the same elevation equivalent to the starting position.
Measuring angles and direction To measure angles between objects and orient there direction the most effective low technology solution is with the use of a compass. For the compass go to the next page.

Vertical Distance = Ground Distance X sin (angle) equation 1
For a calculate the sin of an angle without a calculator please follow this link HERE. 