IAVAT Surveying Practicum
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August 2015
Todd Horton, PE, PLS
Illinois Professional Land Surveyors Association
1

IAVAT Surveying Practicum August 2015
For Use with Adjustable Leg Tripod
1.
With the tripod legs fully extended, mount the instrument on the tripod head.
2.
Move the instrument to a convenient location, and spread the tripod legs evenly apart, keeping the tripod head nearly level.
3.
Plant all three tripod legs firmly into the ground.
4.
For coarse leveling, adjust the leg lengths to move the level bubble partially into the circle.
5.
For fine leveling, center the bubble by adjusting the leveling screws using the left thumb rule.
6.
When the level bubble is centered, turn the instrument 90 degrees and ensure that the bubble returns to the circle. If it does not, adjust the screws and recheck it.
If upon rechecking it is still not level, the instrument may require maintenance.
7.
Point the instrument toward your first rod reading. Use the aiming sight and the slow motion screw for fine adjustments.
8.
Adjust the instrument focus on the rod using the objective focus knob.
9.
Adjust the eyepiece focus by turning the ring surrounding the eyepiece. Test for parallax and adjust eyepiece and objective focus until parallax is eliminated.
10.
After all measurements are complete and before removing the instrument from the tripod, return the leveling screws to their centered positions.
Todd Horton, PE, PLS
Illinois Professional Land Surveyors Association
2

IAVAT Surveying Practicum August 2015
For Use with Fixed Leg Tripod
1.
Mount the instrument on the tripod head with the leveling screws positioned between the tripod legs.
2.
At a convenient location, spread the tripod legs evenly apart, keeping the tripod head nearly level.
3.
Plant two tripod legs firmly into the ground.
4.
Position the instrument eyepiece over the third tripod leg.
5.
For coarse leveling, move the third leg left/right and in/out to move the level bubble close to the circle.
6.
Move the third leg in, thus moving the bubble toward that leg, to compensate for planting the third leg into the ground. Then plant the third leg.
7.
To fine level the instrument, center the bubble by adjusting the leveling screws using the left thumb rule.
8.
When the level bubble is centered, turn the instrument 90 degrees and ensure that the bubble returns to the circle. If it does not, adjust the screws and recheck it.
If upon rechecking it is still not level, notify the instructor.
9.
Point the instrument toward your first rod reading. Use the aiming sight and the slow motion screw for fine adjustments.
10.
Adjust the instrument focus on the rod using the objective focus knob.
11.
Adjust the eyepiece focus by turning the ring surrounding the eyepiece. Test for parallax and adjust eyepiece and objective focus until parallax is eliminated.
12.
After all measurements are complete and before removing the instrument from the tripod, return the leveling screws to the equalized position.
Todd Horton, PE, PLS
Illinois Professional Land Surveyors Association
3

IAVAT Surveying Practicum
August 2015
Todd Horton, PE, PLS
Illinois Professional Land Surveyors Association
4

IAVAT Surveying Practicum August 2015
When demonstrating the process, ask a volunteer to read each step aloud before you perform that step.
Allow students to practice the process in pairs, with one student coaching from the checklist and the other student doing the work. After each successful process, the two students should swap roles and repeat the process.
Returning the leveling screws to their equalized positions is simply adjusting the screws to identical heights. Your instrument may have marks on the leveling screw shafts indicating the center of the adjustment range. Use those as a guide if available.
Remind the students that the level bubble moves to the highest side of the instrument. During coarse leveling, if the bubble aligns with a tripod leg, then shorten that leg until the bubble moves in the desired direction.
Coarse leveling is complete when the bubble no longer touches the wall of the circular level vial. At that point, it should only take small adjustments of the leveling screws to accomplish fine leveling.
Planting the tripod feet fully into the surface prevents settlement and subsequent reading errors.
Todd Horton, PE, PLS
Illinois Professional Land Surveyors Association
5

IAVAT Surveying Practicum
August 2015
1.
Look through the instrument at a the rod. The cross hairs may be only faintly visible or out of focus.
2.
Adjust the eyepiece focus ring until the cross hairs are as dark and as dark as possible. You will probably need to refocus the objective lens to read the rod.
3.
While viewing the rod through the instrument, move your head slightly up and down. If the cross hair appears to move on the rod, then parallax error remains. Repeat step 2 as needed until the cross hair no longer moves on the rod.
Todd Horton, PE, PLS
Illinois Professional Land Surveyors Association
6

IAVAT Surveying Practicum August 2015
Todd Horton, PE, PLS
Illinois Professional Land Surveyors Association
7

IAVAT Surveying Practicum August 2015
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All measurements contain error.
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Some amount of error is acceptable.
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Acceptable error is determined by the intended use of the measurement.
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Good leveling procedures are designed to minimize systematic and random errors.
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Systematic error o Can be measured / quantified o Has a positive or negative value
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Random error o Accidental / blunder o Cannot be measured / quantified
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Systematic o Earth curvature & refraction o Maladjusted instrument o Temperature effect on level rod o Level rod not plumb
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Random o Instrument not level o Bad rod reading o Poor turning point o Parallax o Heat wave effects o Wind effects
Todd Horton, PE, PLS
Illinois Professional Land Surveyors Association
8

IAVAT Surveying Practicum August 2015
Level circuit = series of leveling measurements used to determine the elevation of one or more points.
Station = location
BS = backsight = rod reading at a point of known elevation
FS = foresight = rod reading at a point of unknown elevation
HI = height of instrument = elevation of level crosshair (line of sight)
Benchmark = a permanent point of known elevation.
Turning point = a point temporarily used to transfer an elevation.
Todd Horton, PE, PLS
Illinois Professional Land Surveyors Association
9

IAVAT Surveying Practicum
August 2015
Todd Horton, PE, PLS
Illinois Professional Land Surveyors Association
10

IAVAT Surveying Practicum
August 2015
Todd Horton, PE, PLS
Illinois Professional Land Surveyors Association
11

IAVAT Surveying Practicum
The difference between the top wire and middle wire readings should …
… match the difference between the middle wire and bottom wire readings within
0.01 ft.
The average of the three readings should match the middle wire reading. If not, there is a blunder
Todd Horton, PE, PLS
Illinois Professional Land Surveyors Association
August 2015
Top stadia wire
Main wire
Bottom stadia wire
12

IAVAT Surveying Practicum August 2015
Demonstrate the impact of reading the rod from top to bottom and contrast the results with proper readings.
Demonstrate the ease in misreading the rod by one whole foot.
Allow students to practice rod reading in small groups, with one student randomly pointing with a pencil to marks on the rod while the other students take the reading.
To build student confidence, teach them how to check their results.
When rounding readings to the nearest 0.01 foot, round to the nearest even value.
Unrounded values
Values rounded up
Rounded to nearest even
1.015 ft 1.02 ft 1.02 ft
1.025 ft 1.03 ft 1.02 ft
1.035 ft
1.045 ft
1.055 ft
1.065 ft
Σ = 6.240 ft
1.04 ft
1.05 ft
1.06 ft
1.07 ft
1.04 ft
1.04 ft
1.06 ft
1.06 ft
Σ = 6.27 ft Σ = 6.24 ft
Rounding up produced a cumulative 0.03 ft error.
Todd Horton, PE, PLS
Illinois Professional Land Surveyors Association
13

IAVAT Surveying Practicum August 2015
Using 3 wire readings, measure the elevation difference between the given points. Calculate the distance and slope between the given points.
Top wire
Middle wire
Top wire
Middle wire
Bottom wire Bottom wire
Average reading Average reading
Distance Distance
If (top wire – middle wire) - (middle wire – bottom wire) ≤ 0.01 ft, readings are acceptable.
If (top wire – middle wire) - (middle wire – bottom wire) ≥ 0.01 ft, retake all 3 readings.
Distance = (top wire – bottom wire) X 100
Elevation difference
Horizontal distance
Slope (decimal)
Slope (percent)
Todd Horton, PE, PLS
Illinois Professional Land Surveyors Association
14

IAVAT Surveying Practicum
Known elevation at Benchmark A
Unknown elevation at Benchmark B
August 2015
Must be stable and made of a hard material
Should have a distinct high point to support the level rod
Can be existing features (back of curb, corner of pavement, light pole foundation)
Can be temporary objects driven in soil (top of chaining pin, axe head, cold chisel)
Todd Horton, PE, PLS
Illinois Professional Land Surveyors Association
15

IAVAT Surveying Practicum August 2015
Elevation + BS = HI and HI – FS = Elevation. a.
Calculate all HI’s and elevations. b.
Show the arithmetic check, the resulting closure error, and the allowable error calculation. c.
Circuit length: 3050 feet
Sta BS
BM A 6.77
TP 1 7.45
TP 2 7.07
BM B 1.12
TP 3 2.22
BM A --------
HI FS ELEV
-------- 1231.09
4.23
3.50
5.12
8.35
3.45
Parentheses indicate this value is previously known.
(1231.09)
Starting elevation + sum of BS readings – sum of FS readings = computed ending elevation
Todd Horton, PE, PLS
Illinois Professional Land Surveyors Association
16

IAVAT Surveying Practicum August 2015
This format is commonly used by professional surveyors.
Sta
BM A
TP 1
TP 2
BS HI FS ELEV
6.77 1237.86 -------- 1231.09
7.45 1241.08 4.23 1233.63
7.07 1244.65 3.50 1237.58
BM B
TP 3
1.12
2.22
BM A --------
1240.65
1234.52
5.12
8.35
3.45
1239.53
1232.30
1231.07 (1231.09)
1231.09 + 24.63 -24.65 =1231.07 OK
Actual closure error = calculated ending elevation – known ending elevation
From the example above: 1231.07 – 1231.09 = - 0.02 ft = actual closure error
Allowable closure error CE a
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0 .
05 ft M
CE a
= allowable closure error (feet)
M = circuit length (miles)
The circuit length is the total of all back sight distances and all foresight distances to turning points and benchmarks.
The circuit length can be estimated by scaling from a map or by pacing. When using 3 wire leveling methods, circuit length can be computed from the readings.
For a 3050 foot circuit, CE a
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0 .
05 ft
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3050
5280 ft ft
/ mile
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

0 .
038
If actual closure error < allowable closure error, then circuit is OK.
If actual closure error > allowable closure error, then re-run circuit. ft
Todd Horton, PE, PLS
Illinois Professional Land Surveyors Association
17

IAVAT Surveying Practicum
August 2015
Todd Horton, PE, PLS
Illinois Professional Land Surveyors Association
18

IAVAT Surveying Practicum August 2015
Walk through your level circuit assignment with the students, suggesting locations for turning points and instrument setups.
During differential leveling, remind students to keep back sight distances and foresight distances roughly equal within each instrument setup whenever possible. (These lengths can vary widely from setup to setup.)
This is nearly impossible during profile leveling.
For closed loop differential circuits (starting and ending on the same benchmark), use turning points twice to provide internal checks in the survey. For instance, starting from benchmark A, the turning points may be called TP1, TP2, and TP3 en route to new benchmark B. When returning to A from new benchmark B, use the same turning points in reverse order: TP3, TP2, and TP 1. When all goes well, both of the computed elevations at each turning point should match closely.
However, a large mismatch helps to isolate an error.
Teach students to rock the level rod smoothly through the vertical position. Demonstrate how to stand behind the rod facing the instrument to ensure the rod is plumb in the left-right direction. Encourage students to hold only the rod edges to prevent their fingers from obscuring the marks.
Insist on solid turning points. Poor turning point choices are common error sources for students.
To speed up class activities, try attaching level rods to stationary objects with wire ties and duct tape. This can prevent a traffic jam at the starting benchmark.
Todd Horton, PE, PLS
Illinois Professional Land Surveyors Association
19

IAVAT Surveying Practicum
August 2015
Todd Horton, PE, PLS
Illinois Professional Land Surveyors Association
Side shots are those leveled points on the profile but not on a turning point or benchmark.
They do not affect the closure error in the circuit. Therefore they have no checks on their accuracy.
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IAVAT Surveying Practicum August 2015
Sta BS
BM 403 7.17
0+00
0+20
1+00
TP 1
2+00
5.61
3+00
3+15
TP 2
4+00
4+60
BM 404
0.91
13.69
HI FS
6.82
6.51
4.27
3.02
4.08
5.66
6.11
5.49
4.02
7.87
8.33
16.84
ELEV
589.64
Parentheses indicate this value is previously known.
(586.50)
The circuit length is the total of all back sight distances and all foresight distances to turning points and benchmarks. The circuit length can be estimated by scaling from a map or by pacing.
Sum the all the back sights and the corresponding foresights (shaded boxes) in the example above for the arithmetic check.
For the example above: 589.64 + 13.69 – 16.84 = 586.49
586.49 – 586.50 = - 0.01 ft actual closure error
Todd Horton, PE, PLS
Illinois Professional Land Surveyors Association
21

IAVAT Surveying Practicum August 2015
Brass tablet in concrete Chiseled square Fire Hydrant
Cap nut between E & L in fire hydrant name
Should be durable and permanent
Must be stable, not susceptible to frost heave or settlement
Railroad spike set in power pole or tree
Top of well casing
Building foundation
Building floor
Todd Horton, PE, PLS
Illinois Professional Land Surveyors Association
22

IAVAT Surveying Practicum August 2015
Today more and more of our data is collected electronically, however the field book is still an important part of every survey.
Surveying field notes are the permanent record of work done in the field. If the notes are incomplete, incorrect, or destroyed, much or all of the time spent making accurate measurements may be lost.
The data in field notes is normally used to make a map or to perform computations. Thus, it is essential that notes be clear to others without verbal explanation.
The quality of field notes is measured against these criteria:
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Accuracy : This is the most important quality in all surveying operations.
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Integrity : A single omitted measurement or detail may nullify use of the field notes for plotting or computing.
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Legibility : If they cannot be read, they cannot be used.
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Arrangement : In a simple and straightforward way, they should show the order of the work performed.
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Clarity : Advance planning and proper field procedures are necessary to insure clarity of the notes. Good notes render only one possible interpretation.
Field notes reflect the competency of the surveyor to an even greater extent than does the handling of an instrument. They should be regarded as a permanent record and not merely as memos. Their value will depend largely upon the clearness and completeness with which they are recorded.
Whenever possible, draw sketches for clarity.
The recorder should review the notes to ensure that someone not present at the site can understand the notes with only one possible interpretation.
The competent surveyor builds checks into the work. Plan the field work and notekeeping to include check processes at critical points of the work from start to finish. These can include geometric checks, mathematic checks, quality checks, and procedural checks.
Error management demands a high priority. Plan for check procedures before starting the work.
Todd Horton, PE, PLS
Illinois Professional Land Surveyors Association
23

IAVAT Surveying Practicum August 2015
1.
Letter the name and address of the field book owner on the cover and first page.
2.
Prepare your field book according to these guidelines: a.
Two sheets in a field book comprise one page. The figure below shows one field book page, page number 27, numbered at the upper right corner of the right sheet. b.
Label the first two pages as ‘Index’. As you fill the pages in your field book, add entries in your Index pages summarizing the contents of your field book. c.
Beginning on the third page (fourth sheet) in your field book, number each page in the upper right corner of the right sheet, starting with number 1.
Page number
3.
Titles describing the location and nature of work should be lettered across the top of the left page and may extend to the right page.
4.
The top of the right page should contain: a.
Date of work. b.
Weather (temperature, sky conditions) c.
Crew members (may use initials) d.
Instrument used.
4.
In general, the left page is used for tabulations while the right page is used for sketches and descriptions.
Todd Horton, PE, PLS
Illinois Professional Land Surveyors Association
24

IAVAT Surveying Practicum
5.
Use neat lettering for maximum clarity (see example below).
August 2015
6.
Use 2H pencil lead to minimize smearing. HB lead, commonly provided in mechanical pencils, smears easily.
7.
Begin a new day’s work on a new page.
8.
Always record directly in the field book immediately following a measurement. Nothing should be left to memory or copied from temporary notes.
9.
Do not erase recorded data. Run a single line through an incorrect value (so it is still legible) and place the correct value above or below it. Void an entire page by running diagonal lines to the corners of the page. Never tear pages out of the field book.
10.
Carry a straight edge for ruling lines and a small protractor for laying off angles.
11.
Use sketches instead of tabulations when in doubt.
12.
Make sketches to general proportions, rather than exactly to scale or without plan. Letter parallel with or perpendicular to the appropriate feature.
13.
Exaggerate details on sketches if clarity is thereby improved.
14.
Line up descriptions and sketches with corresponding numerical data.
15.
Avoid crowding, if it is helpful to do so, use several right pages of descriptions and sketches for a single left page.
Todd Horton, PE, PLS
Illinois Professional Land Surveyors Association
25

IAVAT Surveying Practicum August 2015
16.
Use explanatory notes when they are pertinent.
17.
Employ conventional symbols and signs for compactness.
18.
Place north at the top or left side of all sketches if possible and a north arrow must be shown on all sketches.
19.
Keep tabulation figures inside the column rulings, with the decimal points and digits in line vertically.
20.
Make a mental estimate of all measurements before receiving and recording them, to eliminate large errors.
21.
Repeat aloud values given for recording and have it verified by the instrument person.
22.
Place a zero before the decimal point for numbers less than one.
23.
Show the precision of measurements by recording significant trailing zeros.
24.
Do not write one figure over another or on column rulings or lines of sketches.
25.
Make all possible arithmetic checks on the notes and record them before leaving the field.
26.
Title, index, and cross-reference each new job or continuation of a previous one.
27.
Compute all closures and ratios of error before leaving the field.
Todd Horton, PE, PLS
Illinois Professional Land Surveyors Association
26

IAVAT Surveying Practicum August 2015
Todd Horton, PE, PLS
Illinois Professional Land Surveyors Association
27

IAVAT Surveying Practicum August 2015
Todd Horton, PE, PLS
Illinois Professional Land Surveyors Association
28

IAVAT Surveying Practicum August 2015
Todd Horton, PE, PLS
Illinois Professional Land Surveyors Association
29

IAVAT Surveying Practicum August 2015
Todd Horton, PE, PLS
Illinois Professional Land Surveyors Association
30

IAVAT Surveying Practicum
Notes:
August 2015
Todd Horton, PE, PLS
Illinois Professional Land Surveyors Association
31