(3) Leveling Part 2
Transcript of (3) Leveling Part 2
LevelingPart 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
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
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
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
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
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
= 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
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
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
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
= 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
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
Profile Leveling
http://www.blm.gov/pgdata/etc/medialib/blm/wo/MINERALS__REALTY__AND_RESOURCE_PROTECTION_/bmps.Par.47885.Image.-1.-1.1.gif
Leveling plate/turning plate/foot plate
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
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
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
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
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
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
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.
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
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
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
Reference:
Anderson, J.M., Mikhail, E.M. (2002). Surveying: Theory and Practice. 7th ed. WCB/McGraw-Hill.