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8/19/2019 Lecture 02 Differential Levelling
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BRAE 239 – Engineering SurveyingBRAE 239 – Engineering Surveying
Homework “A” Due
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Definitions
• Leveling is used for
Design of improvements
Layout of construction projects
Volume Calculations
Mapping
Monitoring of earth movement
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Definitions
• Datum - vertical A level surface taken as a surface of reference
o NGVD29 – National Geodetic Vertical Datum of 1929
o NAVD88 – North American Vertical Datum of 1988
o Tidal
o Local
o Assumed
• Elevation The vertical distance from the datum
• Benchmark A permanent object, having a marked point whose elevation relative
to a specific datum is known
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Definitions
• Level loop or Level Circuit
The process in leveling of completing a “loop” by always starting on a
point of known elevation and always terminating on a point with a
known elevation
Often can be the same point for both the start and end.
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Field Note keeping
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Field
Note
keeping
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Field Note keeping
• Once the loop is completed you need to Perform a Math Check
o ElevStarting + ∑BS - ∑FS = ELEVEnding
Determine Error of Closure
o |MeasureEndElev – KnownEndElev|
Determine Allowable Error
D0.0014 A.E.
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Field
Note
keeping
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Rod Readings
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Rod
Readings
0.01’
0.01’
1 Foot Marker
0.1’ Marker0.05’ Marker
Rod Reading = 7.24’
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Rod Readings
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Field
Procedures
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Field Procedures
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Field
Procedures
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Field Procedures
• Set the level up equidistant between backsight &foresight
± 30 feet
You do not need to be in line between both points
Make sure you can see both pointso Check with hand level
Do NOT Set up on the Asphalt
• Set the level no further then 150 feet from either
backsight or foresight
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Field
Procedures
• Before moving the level
Make sure you have all the readings needed from your
current location
o Backsight
First reading after setup
o Foresight
Second reading after setup
Make sure the rod stays at the foresighto This will be your next Backsight Reading
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Field Procedures
• When moving
Keep the level upright
• When using a Turning Point Spike
Set the Spike so it is solid in the Ground
Set the rod on top of the Spike when reading the rod
Leave something by the spike so you can find it
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Field
Procedures
• Always Turn through a point
This means after you take a foresight reading on a pointo You move the level before you take your backsight reading
• Check your Error of closure in the field
Make sure it meets the allowable error
If noto Run each section of the loop and check to see if that solves the
problem
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Lab 03
• You will be workingover at the Sportsfield Area
• You will determinethe elevations ofPoints C & D foryour Crew NumberYou will start on
Benchmark SF-1oElevation 322.42’
First go to the “D”Point
Then go to C point
Finally close backon SF-1
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Field
Procedures
• ShowNorth
General Area
Location of MonumentsoMonument is any relatively permanentobject that you measure to
Description of MonumentsoWhat physically is the monument
Swing Ties to MonumentsoTwo distance ties
To the nearest 0.10’
Tie out Both “D” and “C”Monuments
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Lab 03
• Party Chiefs You will need to check out on the Equipment card
o Field Box
o Automatic Level
o Tripod
o Philadelphia Rod
Put your party No, Date (January 5, 2016), and your name
• Crews make sure you have Equipment
Note keepers field book o Note the Serial Number of the Level in your books
Lab instructions
Calculator
• The Room will be locked up
No one gets in untilo I get back from the field
So there is no reason to rush