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Leveling Part 2

(3) Leveling Part 2

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Page 1: (3) Leveling Part 2

LevelingPart 2

Page 2: (3) Leveling Part 2

Methods in Leveling

1. Direct or Spirit Leveling

2. Indirect or Trigonometric Leveling

3. Stadia Leveling

4. Barometric Leveling

5. Gravimetric Leveling

6. Inertial Positioning System

7. GPS Survey

OUTLINE:Methods in Leveling

Direct Leveling

Trigonometric Leveling

Stadia Leveling

Barometric Leveling

Gravimetric Leveling

Inertial Positioning System

GPS survey

Page 3: (3) Leveling Part 2

1. Direct (Spirit) Leveling measuring vertical distances directly most precise method commonly used

a) Differential Leveling – determining the elevation of points some distance apart.

b) Double Rod Leveling – employing two level routes simultaneously.

c) Three-wire Leveling – three horizontal hairs are read and recorded.

d) Profile Leveling -- determining the elevation of points at short measured intervals along a fixed line.

e) Reciprocal Leveling

OUTLINE:Methods in Leveling

Direct Leveling

Trigonometric Leveling

Stadia Leveling

Barometric Leveling

Gravimetric Leveling

Inertial Positioning System

GPS survey

Page 4: (3) Leveling Part 2

Differential Leveling

Requires a series of set ups of the instrument along the general route and, for each set up, a rod reading back to a point of known elevation and forward to a point of unknown elevation

CHECKS:

1. Rerunning levels on the same route

2. “Tying on” to a previously established BM near the end of the level line

3. Returning to the initial BM level loop

OUTLINE:Methods in Leveling

Direct Leveling

Trigonometric Leveling

Stadia Leveling

Barometric Leveling

Gravimetric Leveling

Inertial Positioning System

GPS survey

Page 5: (3) Leveling Part 2

Double Rod Leveling

BM1(known)

TP1 H

TP1 L

TP2 L

TP2 L

BM2 (unknown)

OUTLINE:Methods in Leveling

Direct Leveling

Trigonometric Leveling

Stadia Leveling

Barometric Leveling

Gravimetric Leveling

Inertial Positioning System

GPS survey

Page 6: (3) Leveling Part 2

STA. B.S. H.I. F.S. ELEV.

BM 131.768 228.372

1.768

TP1 H 2.732 2.137

TP1 L 3.079 3.488

TP2 H 2.366 1.674

TP2 L 3.024 2.329

BM 140.946

1.442

Double Rod LevelingOUTLINE:Methods in Leveling

Direct Leveling

Trigonometric Leveling

Stadia Leveling

Barometric Leveling

Gravimetric Leveling

Inertial Positioning System

GPS survey

Page 7: (3) Leveling Part 2

provides a continuous check on the process of determining ground elevations while the work is in progress

USEFUL WHEN:

There is an urgent need to undertake differential leveling in a short period of time where no established bench marks are available for checking results.

Running a long line of levels which do not close back on the initial BM

Double Rod LevelingOUTLINE:Methods in Leveling

Direct Leveling

Trigonometric Leveling

Stadia Leveling

Barometric Leveling

Gravimetric Leveling

Inertial Positioning System

GPS survey

Page 8: (3) Leveling Part 2

= Precise form of differential leveling

Requirements:

1. Rod should be calibrated at frequent intervals by comparison with a standard length.

2. Rod should have an attached rod level for plumbing.

Three Wire LevelingOUTLINE:Methods in Leveling

Direct Leveling

Trigonometric Leveling

Stadia Leveling

Barometric Leveling

Gravimetric Leveling

Inertial Positioning System

GPS survey

Page 9: (3) Leveling Part 2

3. Level must be equipped with stadia hairs

Mean of the readings is taken as correct rod reading for each sight

4. Level should be protected from the sun by an umbrella

5. Level tripod should be set very firmly on the ground to prevent settlement

6. Shortest possible time elapse bet. BS & FS is desirable in order to eliminate, as nearly as possible, the effects of:

variations in atm. Refraction

Settlement of the tripod

Warping of the level

Three Wire LevelingOUTLINE:Methods in Leveling

Direct Leveling

Trigonometric Leveling

Stadia Leveling

Barometric Leveling

Gravimetric Leveling

Inertial Positioning System

GPS survey

Page 10: (3) Leveling Part 2

Three Wire Leveling

BACKSIGHT FORESIGHT

STA. HAIR RDGS MEAN RDG S H.I. F.S. MEAN RDG S ELEV.

BM1

1.152

444.2420.935

0.718

TP1

2.784 1.117

2.420 0.899

2.057 0.682

TP2

1.713 1.900

1.440 1.537

1.166 1.172

BM2

1.450

1.177

0.904

OUTLINE:Methods in Leveling

Direct Leveling

Trigonometric Leveling

Stadia Leveling

Barometric Leveling

Gravimetric Leveling

Inertial Positioning System

GPS survey

Page 11: (3) Leveling Part 2

STA.

Thread Rdg

(mm)Mean (mm)

Middle Thread

(ft) Thread Interval

Σ Intervals

Rod No. & Temp

Thread Rdg

(mm)Mean (mm)

Middle Thread

(ft) Thread Interval

Σ Intervals

2037 194 A 0850 0209

1 1843 1843 6.04 195 22 ͦC 0641 06403 209 0211

1648 389 389 0430 0420 0420

Three Wire Leveling

Page 12: (3) Leveling Part 2

= process of determining elevation of points at short measured intervals along a fixed line

stakes or other marks are placed @ regular intervals along an established line, usually the center line.

ordinarily the interval bet. Stakes is 100m, 50m, 20m and 10m.

Used during the location and construction of the ff.:

1. Highways

2. Railroads

3. Canals

4. Sewers

Profile LevelingOUTLINE:Methods in Leveling

Direct Leveling

Trigonometric Leveling

Stadia Leveling

Barometric Leveling

Gravimetric Leveling

Inertial Positioning System

GPS survey

Page 13: (3) Leveling Part 2

Profile Leveling

STA. B.S. H.I F.S. I.F.S ELEV.

BM 30 3.478 33.478 30.000

0 + 00 3.617

0 + 00 5.141

+ 10 1.720

TP 1 3.314 0.913

+ 20 2.860

+ 29.5 1.852

+ 30 1.805

TP 3 0.081 2.289

TP 4 0.333 3.661

BM 30 1.974

OUTLINE:Methods in Leveling

Direct Leveling

Trigonometric Leveling

Stadia Leveling

Barometric Leveling

Gravimetric Leveling

Inertial Positioning System

GPS survey

Page 14: (3) Leveling Part 2

Profile Leveling

http://www.blm.gov/pgdata/etc/medialib/blm/wo/MINERALS__REALTY__AND_RESOURCE_PROTECTION_/bmps.Par.47885.Image.-1.-1.1.gif

Page 15: (3) Leveling Part 2

Leveling plate/turning plate/foot plate

Page 16: (3) Leveling Part 2

STA. B.S. H.I. F.S ELEV.BM1 1.256 127.133TP1 1.116 1.886 126.503

BACKSIGHT FORESIGHT

STA. HAIR RDGS

MEAN RDG S H.I. F.S. MEAN

RDG S ELEV.

BM11.152

444.242

0.9350.718

TP1

2.784 1.1172.420 0.899

STA. B.S. H.I. F.S. ELEV.

BM 131.768 228.3721.768

TP1 H 2.732 2.137TP1 L 3.079 3.488TP2 H 2.366 1.674

STA. B.S. H.I F.S. I.F.S ELEV.

BM 30 3.478 33.478 30.000

0 + 00 3.617

+ 10 5.141

+ 20 1.720

Page 17: (3) Leveling Part 2

Reciprocal Leveling= used in determining relative elevations of 2 widely

separated intervisible points between which levels cannot be run in the ordinary manner.

http://www.tpub.com/content/engineering/14069/css/14069_481.htm

OUTLINE:Methods in Leveling

Direct Leveling

Trigonometric Leveling

Stadia Leveling

Barometric Leveling

Gravimetric Leveling

Inertial Positioning System

GPS survey

Page 18: (3) Leveling Part 2

2. Trigonometric Leveling

zenith or vertical angle AND horizontal or slope distance

difference in elevation is calculated

USE:

Furnishes a rapid means of determining elevations of points in rolling terrain.

OUTLINE:Methods in Leveling

Direct Leveling

Trigonometric Leveling

Stadia Leveling

Barometric Leveling

Gravimetric Leveling

Inertial Positioning System

GPS survey

Page 19: (3) Leveling Part 2

3. Stadia Leveling

consists of observing through the telescope, the apparent locations of two stadia hairs on the rod, which is held in a vertical position.

OUTLINE:Methods in Leveling

Direct Leveling

Trigonometric Leveling

Stadia Leveling

BACKSIGHT FORESIGHT

STA. INTERVAlVERT.

ANGLE ROD RDG VD INTERVAlVERT.

ANGLE ROD RDG VD ΔELEV ELEV

Page 20: (3) Leveling Part 2

4. Barometric Leveling

measuring the differences in atmospheric pressure at various stations by means of a barometer.

pressure is inversely proportional with elevation.

USE:

Principally on exploratory or reconnaissance surveys .

OUTLINE:Methods in Leveling

Direct Leveling

Trigonometric Leveling

Stadia Leveling

Barometric Leveling

Gravimetric Leveling

Inertial Positioning System

GPS survey

Page 21: (3) Leveling Part 2

OUTLINE:Methods in Leveling

Direct Leveling

Trigonometric Leveling

Stadia Leveling

Barometric Leveling

Gravimetric Leveling

Inertial Positioning System

GPS survey

4. Barometric Leveling

Example:

Given the elevation of an upper base of 275 ft, of a lower base of 56ft; the difference in elevation between the bases, therefore is 275 – 56 f= 219 ft. At a given instant, the three altimeter readings indicate that the difference in elevation of an intermediate point from the upper base is 209 ft. and from the lower base is 25 ft; therefore, the indicated total difference in elevation between bases is 234 ft. The corrected differences in elevation are approximately (219/234)(209) = 196 ft (from the upper base) and (219/234)(25) = 23 ft (from the lower base); as a check, the total computed difference in elevtaion between bases is now 196 + 23 = 219 ft. The elevation of the point is 79 ft, computed by difference from either base (275 – 196 = 79 ft; or 56 + 2).3 = 79 ft

Page 22: (3) Leveling Part 2

OUTLINE:Methods in Leveling

Direct Leveling

Trigonometric Leveling

Stadia Leveling

Barometric Leveling

Gravimetric Leveling

Inertial Positioning System

GPS survey

4. Barometric Leveling

QUIZ:

Given the ff data gathered from an altimeter survey:

Elevation of the upper base is 518m; elevation of the lower base is 122m; barometer reading at the upper base is 2708Pa and barometer reading at the lower base is 5954Pa. If the barometer reading at a field station is 4150Pa, determine the elevation of the station.

Page 23: (3) Leveling Part 2

5. Gravimetric Leveling

measuring the differences in gravity at variousstations by means of a gravimeter for geodetic purposes.

OUTLINE:Methods in Leveling

Direct Leveling

Trigonometric Leveling

Stadia Leveling

Barometric Leveling

Gravimetric Leveling

Inertial Positioning System

GPS survey

http://images.google.com/imgres?imgurl=http://www.ngs.noaa.gov/GRD/GRAVITY/Images/fg5.jpg&imgrefurl=http://www.ngs.noaa.gov/GRD/GRAVITY/ABSG.html&usg=__AFyxTSbmapQD4eb4je83y6LNkI0=&h=496&w=394&sz=26&hl=en&start=11&um=1&tbnid=RPEyv1ZAdN5V0M:&tbnh=130&tbnw=103&prev=/images%3Fq%3Dgravimeter%26hl%3Den%26rls%3Dcom.microsoft:en-us:IE-SearchBox%26rlz%3D1I7ADRA_en%26sa%3DN%26um%3D1

Page 24: (3) Leveling Part 2

6. Inertial Positioning System

inertial platform has three mutually perpendicular axes, one of which is “up”, so that the system yields elevation as one of the outputs.

Vertical Accuracy: 15-50cm in distances of 60-100km

Cost: Extremely High applications are restricted to very large projects where terrain, weather, time andaccess impose special constraints on traditional methods.

OUTLINE:Methods in Leveling

Direct Leveling

Trigonometric Leveling

Stadia Leveling

Barometric Leveling

Gravimetric Leveling

Inertial Positioning System

GPS survey

Page 25: (3) Leveling Part 2

7. GPS Survey

use of Global Positioning System

elevations are referenced to the ellipsoid

OUTLINE:Methods in Leveling

Direct Leveling

Trigonometric Leveling

Stadia Leveling

Barometric Leveling

Gravimetric Leveling

Inertial Positioning System

GPS survey

Page 26: (3) Leveling Part 2

Reference:

Anderson, J.M., Mikhail, E.M. (2002). Surveying: Theory and Practice. 7th ed. WCB/McGraw-Hill.