Introduction
What is surveying?Collection, processing & management of spacial information |
Why is it important?Land ownership, engineering, mining, marine navigation, mapping,etc. |
What is geomatics?Study of Earth |
What is geosensing?measurement of the Earth from remote, moving platforms |
To define a horizontal plane: vertical axis matches gravity vector.Plane tangent to level surface.Long distances you can't use earth as a plane, need to account for the curvature |
the vertical rate of change is higher than horizontal |
vertical/elevation angle: angle to a point with respect to horizontal plane |
zenith angle:angle to a point with respect to the zenith (vertical direction) |
horizontal angle: angle between two points measured in the horizontal plane |
Field notes:accuracy, integrity, legibility, arrangement, clarity.Pencil.Cross mistakes.Evidence |
Module 2 - leveling
Process of determining elevation (heights) or difference in elevation |
level surface: curved surface orthogonal to plum line everywhere |
vertical line: direction of gravity(indicated by plumb line) |
collimation axis: horizontal plane of instrument |
vertical datum: any level surface to which heights are referred |
mean sea level: mean height of ocean level taken from 26 gauges over 19 years |
tidal datum: avg. of all high water over 19 years |
elevation: vertical distance above datum |
BM: permanent monument which elevation is known |
earth curvature |
systematic error. if BS&FS distances are the same then effect is cancelled |
refraction |
difference in temperature & pressure with altitude riser difference in refraction index of atm. systematic error. |
meter |
feet |
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Instrumentation
height difference:dumpy, tilting, automatic level |
distance:steel band (account T & Fpull);nylon tape;electronic distance measurement |
angular:theodolite;electronic theodolite |
distance+angular:total station |
other:global positioning system(gps);laser scanner |
Module 1
Significant Figures SG |
accuracy: #of digits recorded |
add/substract:leftmost,rightmost sg |
multiplication:least #sg of factors |
Errors |
Sources:natural, instrumental &personal |
-mistakes/gross error or blunder. ex:read a tape incorrectly |
-systematic. physical or geometric law can correct. ex:thermal expansion of steel band |
-random. can't be corrected or modeled. |
Precision&Accuracy |
accuracy: nearness to true value. error is random. |
precise: consistency of a group of observations, may contain systematic error |
probability (most probable #)Dbar=(∑D/n) ; (residual) ν=Dbar-D |
surveys contain redundant info: analysis of residuals for accuracy and remain systematic error. more equation than unknowns assumes normally distributed random error. |
error propagation |
root mean² error RMSE=√((∑Dbar-D)²/n) |
standard deviation σ=±√((∑ν²)/(n-1)) |
Module 6
Lidar: light detection and ranging. Mainly concerned with the precise timing and range determination of the return signal. generally based on pulse lasers |
Laser: light amplification by stimulated emission of radiation. safety concerns: MPE (max. permissible exposure) parameter: exposure duration/pulse width |
Cadastral surveying
tenure: legal structure by which land is owned |
Land tenure components: |
1- method of transferring ownership (title) via deeds (written documents which contain description of the property) |
2- permanently marked boundaries on the ground |
3- officially maintain ownership records. (county clerks office or US bureau of land management-BLM) |
4-official legal description |
common law: law that has been developed on the basis of preceding rulings by judges |
statutory law: written laws passed by legislative and government of a country and those which have been accepted by society |
Types of cadrastral surveying: |
1- original: land has not yet been measured and lines of ownership set |
2- retracement: purpose of relocating ore reestablishing previously surveying boundary lines. restore boundary markers to their original location, not to correct them. General priorities: senior rights; intent of parties; call for a survey; monuments (natural, artificial); measurements (distance, direction, area, coordinates) |
3- subdivision survey: establish new smaller parcels of land within lands already surveyed |
property description methods: |
1- metes and bounds: Colonial method. giant description. start with a point of commencement (POC) |
2- block and lot: reference a plat that has been filed in the clerks office. simple, concise and fewer conflicts. descriptions usually created simultaneously and thus are not subjected to senior rights: excess or deficiency found in prorated equally. |
3- coordinates: state plane coordinates. Pros: virtual monument that does not degrade; easily re-established; concise. Cons: reference/datum is not static due to earth movement. |
4- public land survey system PLSS |
Adverse possession: gain title to a land that is not yours. requirements: actual possession; exclusive possession; open & notorious possession; hostile possession; continuous possession(depends on state). may require a "color of title" (claim to a parcel of real property based on some written instrument, though a defective one) |
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Units of Linear measurement
1m=100cm=1000mm |
1km=1000m |
1ft=0.3048m[international] |
1in=25.4mm |
1ft=12in |
1ch=20.1168m=66ft |
1yard=3ft |
1mile=5280ft=80ch |
1nautical mile=6076.10ft |
1ha=10000m²=100mx100m |
1ac=1chx10ch |
1ac=43560ft²=66ftx660ft |
1ac=0.4047ha |
degree=(radx180°)/π |
rad=(degree*π)/180° |
0.1°=6' |
0.01°36'' |
0.001°=3.6'' |
0.0001°=0.36'' |
1rad=57.2958°=206264.8" |
Module 3
Chaining: nylon tape/steel band. Error: incorrect length, temperature, incorrect tension. |
Edm:classified accord: |
1- radiation source: optical or microwave |
2-measurement principal: phase difference or pulse |
pulse method: Problems: energy does not behave like a box. gaussian shape signal processing issue. more convenient type but not as accurate |
phase method: ambiguity: unknown integer # of cycles between the instrument & reflector. Large wave lengths could measure distance without amb. Since n=0 when your are within one cycle |
3- wheter a reflector is requires or not |
Module 7
Compound curve: different radius of curvature |
broken-back curve: 2 difference curves connected by a tangent |
reverse curve: S shape |
spiral: has variable radius of curvature and provides a smooth transition from tangent to a certain radius of curvature |
centripetal: force you car feels toward the center of radius of curvature. Counter-balanced by: superelevation (e) and side friction factor (fc) |
centrifugal: imaginary force that drivers feel pushing them outward due to frame of reference. |
Superelevation: limits related to: climate, terrain conditions, type of area, frequency of slow moving vehicles |
side friction: used to maintain path on curve. |
PLSS
why? recognition of the value of grid-system subdivision and need of the colonies to revenue from the sale of public lands |
designed to maximize number of regular sized sections and minimize field work |
boundaries: unchangeable. |
1mile=80chain and 1acre=10ch^2 |
broken into: quadrangles;townships;section;1/4section |
discrepancies thrown into sections bordering NW township |
surveys proceed S->N and E->W |
Colonial survey: metes & bounds. often dictated by the topography and other pre-existing landmarks |
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Module 4
Bearing: horizontal angle between the line and the chosen direction north |
Azimuth: bearing referred to true north |
deflection angle: counter-clock angle. note: back bearing: forward +180° |
compass: angular survey measurement. bearing wrt magnetic N |
geodetic azimuth: magnetic azimuth+declination. Magnetic pole is always moving, declination not constant |
agonic line: zero declination, mag & rotational pole at the same meridian |
angular measurement: theodolite levelled so that horizontal angle or directions are measured in horizontal plane. |
double centering: angles are measured twice: face left and face right (rotated 180°). Eliminating systematic errors |
closing the horizon: method which all angles at a station are measured |
theodolite errors:collimation error: systematic. the collimation axis is not orthogonal to the trunnion axis. Collimation axis traces out a flat cone rather than a vertical plane. |
Module 5
Traversing: control for construction set-out. cadastral surveys to locate or establish boundaries. |
traverse station: temporary or permanent point of the traverse |
Module 8
Low point: defines location of catch basin for drainage |
high point defines limits of drainage area for roadways |
Design of vertical curve |
crest: sight distance, appearance, safety, comfort |
sag: headlight sight distance, rider comfort, drainage, appearance |
comfort: change in grade, design speed |
appearance: change in grande |
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