Abney Level, Glossary and Terms, Amusement, Recreation & Ticket Services
List of United States Amusement & Recreation Services, Ticket Service, Guide Service
"Abney Level" - Amusement Glossary Terms and Abbreviations
Hand-held instrument that is adjusted like a sextant and can be set to a fixed gradient. The user sights through the Abney to a fixed reference (usually a second person) until the crosshair bisects the bubble, this indicates the preset grade.