Profile and
Differential Leveling
AGME 1613
Fundamentals of AST
Objectives
• Define differential and profile leveling, and
explain the purpose(s) and agricultural
applications of each.
• Identify and correctly set-up and use leveling
equipment.
• Properly record leveling field notes and perform
error checks for differential and profile leveling
surveys.
• Complete differential and profile leveling surveys.
Leveling
Definition and Types
• A surveying procedure used to determine
the elevation of points on the Earth’s
surface.
– Differential Leveling
– Profile Leveling
Differential Leveling
Purpose is to determine the difference in
elevation between two (or more) points on the
Earth’s surface.
B
Difference?
A
Where is Differential
Leveling Used?
• Determining field slope (conservation plans,
soil loss prediction, etc.).
• Laying out and checking drainage ditches,
waterways, tile drainage systems, etc.
• “Cut-and-fill” requirements for building
foundations.
• Establish new “benchmarks” that have
elevations tied in with existing benchmarks.
Profile Leveling
Purpose is to describe the elevation at selected
points on the Earth’s surface.
X
X
B
X
X
X
X
A
X
X
X
X
Where is Profile
Leveling Used?
• Developing field “contour maps.”
• Designing and checking grade for drainage
ditches and waterways.
• Laying out farm ponds.
• Road and highway construction.
Leveling Equipment:
The Engineer’s Level
• Telescope with “crosshairs.”
• Base plate – attaches level to
tripod.
• Leveling screws – allows
user to establish a “level line
of sight.”
• Level bubble – Instrument is
level when bubble is inside
target.
• Focusing knob
Leveling Equipment:
Tripod and Leveling Rod
Reading the Leveling Rod
Hundredths (.01) of a foot
Tenths (.10) of a foot
Feet
1
6
.10
.01
.02
.03
.04
.05
6.00-ft.
.06
.07
.08
.09
Reading the Leveling Rod
Feet = 6
Tenths = .0
Hundredths = .09
Crosshair
Reading = 6.09 ft.
Reading the Leveling Rod
3
Direct Differential Leveling
“What is the difference in elevation between two points,
Where both points can be “shot” from the same
location?”
6.45
B
A
Direct Differential Leveling
3.21
B
A
Direct Differential Leveling
• Difference in Elevation
– Rod reading at A = 6.45
– Rod reading at B = - 3.21
Difference in elevation =
3.24-ft
Which point is higher, A or B?
B
A
Leveling Terms
•
•
•
•
•
•
Station (STA)
Benchmark (BM)
Backsight (BS)
Height of Instrument (HI)
Foresight (FS)
Elevation (ELEV)
Leveling Terms
• Station (STA)
– Point where the rod is placed for a
reading
– Stations typically use a “distancenumbering” identification system:
• STA 0 + 00 = 0 hundred feet + 0 feet
• STA 2 +75 = two hundred feet + 75 feet
• STA 5 + 05 =?????????
Leveling Terms
• Backsight
– A rod reading taken on a point of
known elevation:
• BM
• TBM
• Turning Point (TP)
Leveling Terms
• Benchmark (BM)
– A point of known elevation used as a reference point
in a leveling survey.
– A BM has a precisely known elevation above “mean
sea level.”
– Established by a variety of government agencies.
• Temporary Benchmark (TBM) – Point of
“assumed” elevation. Commonly used in “onfarm,” local surveys.
Leveling Terms
• Height of Instrument (HI)
– Height (elevation) of the level’s line of
sight.
• HI = BS + Known Elevation
Determining HI
HI = 100.00 ft + 4.35 ft = 104.35 ft
4.35
HI = Elev + BS
BM-1
Elev = 100.00 ft.
Leveling Terms
• Foresight (FS)
– Rod reading taken on a point of unknown
elevation
• HI – FS = Elev
Determining Elevation
HI = 104.35 ft
6.35
Elev = HI - FS
Elev = 104.35 ft. – 6.35 ft. = 98.00 ft.
Leveling Terms
• Elevation (ELEV)
– Vertical distance above “mean sea level”
of a point on the earth’s surface.
– Depending on purpose of survey, may be
determined to nearest:
.1 –ft
.01 – ft.
.001 –ft.
Differential Leveling Field Notes
STA
BS
HI
FS
ELEV
Dist.
Differential Leveling
3.21
TBM-1
BM-1
Elev = 1225.50 ft.
Differential Leveling
3.01
TBM-1
BM-1
TP-1
Differential Leveling
6.04
TBM-1
BM-1
TP-1
Differential Leveling
0.28
TBM-1
BM-1
Differential Leveling
6.45
TBM-1
BM-1
Differential Leveling
10.98
TBM-1
BM-1
TP-2
Differential Leveling
3.95
TBM-1
BM-1
TP-2
Differential Leveling
5.36
TBM-1
BM-1
TP-2
Error of Closure
• Difference in the “beginning” and “ending”
elevation of a known point.
• All surveys will have error.
• The question is, “How much error can we
tolerate in our survey?”
Error Check
• Mathematical Error Check
Error of closure = |SBS - SFS|
• Allowable Error Check
– Depends on purpose of the survey
– Maximum feet of error based on distance
AE = 0.10 √
M
Profile Leveling Field Notes
STA
BS
HI
FS
ELEV
Simulated Profile Survey
5
4
3
TBM-A (Elev = 100.00)
2
3
1
STA. 0+00
5
9
STA. 1+00
4
6
3
STA. 1+35
2
3
2
STA. 2+00
9
7
8
STA. 2+00
0
4
3
STA. 2+75
0
2
1
STA. 2+95
1
2
STA. 2+95
12
9
8