Topic 2 – Take Rod Readings and Calculate Elevations
A leveling rod consists of multiple sections and rods are various lengths. Like a carpenter’s tape measure, rods can be in feet, inches and fractions (architectural) or in metric. Alternatively, Engineer’s rods can be used which are divided into feet and decimal feet. The markings on a leveling rod will vary in thickness to match the increments used.
A single elevation can be found by adding the benchmark to the backsight reading to determine the Instrument height. Then a foresight reading is taken to the desired location. This reading is either added (location is below the instrument) or subtracted (rod is inverted) from the Instrument height
For more details, review Instruction Sheet (IS) on Brightspace:
CNST 102 (p. 40 – 46, 51 – 54)
IS 3.2 Levelling Rods
IS 4.2 Calculate Elevations
For additional information and terms used for operating the builder’s level refer to Carpentry Chapter 27 – Leveling and Layout Tools.
Review Questions
Record the readings on the following rods:
B)
C)D) (Imperial)
With the telescope of the builder’s level positioned 1150 mm above the elevation of the bench mark, what figures on the rod should be brought into the line of sight to establish an elevation 2200 mm below the B.M?
With the builder’s level set up 1270 mm over the B.M. (10 000 mm) and with a reading of 1602 mm obtained when the rod is placed upside down against a ceiling, what is the elevation of the ceiling?
What is the elevation of the top of a footing if the reading 4394 mm is obtained when the rod is placed on top of the footing and the instrument is set up 356 mm above the B.M (10 000 mm)?
With the instrument set 1478 mm above a B.M. (10 000 mm), what reading would be placed on the rod to establish a finish elevation of 9400 mm at the bottom of an excavation?
With the builder’s level positioned 711 mm above the benchmark and a reading of 1097 mm is obtained when the rod is placed on a finish floor, what is the elevation of the finish floor if the B.M. is 10 000 mm?
When the instrument is set up 1372 mm above a B.M. (10 000 mm), what is the elevation of the top of a column if the inverted rod reading is 3278 mm?
Using the setup shown below in figure 66, calculate on the field book sheet the elevations of stations 1, 2, and 3.
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Station |
B.S. |
I.H. |
F.S. |
ELEV. |
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B.M. |
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Using the diagram below, find the elevations of stations 1-4:x
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Station |
B.S. |
I.H. |
F.S. |
ELEV. |
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B.M. |
—- |
—- |
—- |
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