Elevation

5. A type of level that automatically maintains a horizontal line of sight using a compensator, even if the instrument is slightly out of level.
7. An intermediate reference point used when it is necessary to move the instrument ahead while running a line of levels.
8. An optical instrument used to establish horizontal planes, set up level points, and check elevations.
9. Holds the instrument in the horizontal position when tightened.
10. An instrument designed to project a level line of sight, consisting of a telescope and spirit level vial.
14. The average height of the sea's surface at all tidal stages over a period of 19 years, used as a vertical datum.
15. A prismatic device in an automatic level that uses gravity to maintain a horizontal line of sight.
16. A relatively permanent object with a known elevation, used as a reference point in surveying.
17. The process of determining the elevation of a new point from the known elevation of an existing point.
19. A rod reading taken on a point to determine its elevation; always subtracted from the Height of Instrument.
20. A simple leveling device used in construction when a high degree of accuracy is not required.
21. A graduated pole or stick used with a surveyor's level to measure differences in elevation.
23. A commonly used type of leveling rod in construction surveying.

1. A vial containing liquid and a bubble, used to level the telescope on its base.
2. Definite point between which lengths are measured.
3. The elevation of the level line of sight projected by the instrument, when properly set up.
4. Vertical distance above a reference datum, such as mean sea level.
6. Short horizontal lines located above and below the crosshair in the telescope eyepiece, used to estimate the distance of the object being sighted.
11. A rod reading taken on a point of known elevation (benchmark); always added to the known elevation to calculate the Height of Instrument.
12. A technique where the rod is slowly swung back and forth to ensure the lowest (most accurate) reading is observed.
13. Allows the instrument to be adjusted horizontally.
18. Screws used to adjust the level and center the bubble in the spirit vial, ensuring the telescope is level.
22. Moves when the telescope is turned to the left or to the right.