principios de medidas topograficas

8/4/2019 principios de medidas topograficas

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Principios de Agrimensura yLevantamientos Topogrficos


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Topografa

Es el arte y ciencia de medir y localizar puntos y ngulos sobre ydebajo de la superficie terrestre.

Ejemplos:

1. Determinar la localizacin de puntos sobre la superficie terrestre.

2. Determinar la elevacin de puntos.

3. Recabar datos de campo para dibujar planos.

4. Dibujar en un plano la localizacin de construcciones.

5. Calcular la distancia entre dos puntos.

6. Determinar la posicin de lmites de terrenos.

7. Determinar las reas de porciones de terreno.


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Algunos tipos de levantamientos

1. Control

2. Catastrales, lotificaciones,deslindes, fincas

3. Topogrficos

4. Hidrogrficos5. Construcciones

6. Aereos o fotogramtricos

7. Distancias

8. ngulos9. Nivelaciones

10. Perfiles


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DATOS

The intended use of the data must be known before it is collected.

Determines the equipment that should be used.

Influences the methods that are used.

Two important characteristics

Integrity

Correct

Integrity: an unimpaired condition; soundness

Correct: performing to an approved or

conventional standardWhat is the standard for surveying?

59 O.S. 471.1 et seq, Chapter 245:15-13-2.


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ERRORES

Tipos de errores1. Aleatorios

2. Sistemticos

3. Naturales

4. Personales

Aleatorios No son predecibles

Tienden a ser pequeos y a cancelarse a simismos

Pueden controlarse repitiendo las mediciones

Sistematicos Usually caused by damaged

equipment.

Error tends to multiply (occur

for each measurement)

Best control is calibration of

equipment.

Naturales Factors in the environment that

can cause error.

Curvature

Refraction

Must use correction values

Personales Comunmente llamados

equivocaciones

Se controlan siguiendo los

procedimientos


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Acerca de los datos de las medidas

Exactitud y Precisin Exactitud: el nmero de dgitos significativos en la medida

Precisin: la unidad de la medida

Regla nmero 1 de la topografa

Es mejor un dato incorrecto que carecer del


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Trminos comunes en topografaEsferoide achatado

Nivel

Linea vertical

Plano vertical

Linea horizontalPlano horizontal

Superficie de nivel

Planimetra

Levantamiento geodsicoDistancia horizontal

Plano horizontal

ngulo horizontal

ngulo vertical

Horizontal Aero

Zenith zero

Banco de nivel

Elevacin

Punto de atras

Punto de adelanteTurning point

Balancing sights


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Nivel

The term level is used compare the relative position of an objectwith the horizon or the relative position of two or more objects.Two objects that are level are parallel with the horizon and mayor not be at the same elevation.Los puntos que estn en el mismo nivel, tienen la misma

elevacin.Level is usually determined by an air bubble in a smallcontainer of liquid.


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Nivel (cont.)

The container is usually either a tube orcylinder.

Este dispositivo es comunmente llamado nivel deburbuja o simplemente nivel

The spirit level by itself is not a useable tool. It is usually incorporated withadditional tools, for example, a carpenters level, or a survey level.


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Objects are also level if they are perpendicular to a vertical line.

A vertical line can be established

with a plumb bob or a piece of

string with a weight.

Level cont.


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Horizontal Distance

Distance is the amount of separation between two points, measured

along the shortest path joining them or the size of an object.

A horizontal distanceis a distance measuredon a horizontal line orplane.


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Horizontal PlaneA horizontal plane is a plane that

is perpendicular to a vertical line.

The line of sight through a level

instrument forms a horizontal

line.


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Multiple planes

Each horizontal plane has

a unique elevation above

or below the reference

elevation.

An infinite number of planes at different elevations may exist at anypoint.


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Bench Mark

A benchmark is physicalstructure with a known orassumed elevation.

To be considered a benchmark

the point should be identified bya permanent or semi-permanentstructure that will not beaffected by frost heave, trafficvibrations or environmental

changes.

Surveying standards havevery specific guidelines onthe required structure for

benchmarks.


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Elevation

Elevation is the distance above or below a reference level surface.

The most commonly used reference level surface in the U.S. is the

National Geodetic Vertical Datum of 1929.

Established by connecting 26 tidal benchmarks along the Atlantic,

Gulf ofMexico and Pacific Coasts, this datum is the zero elevation

reference point used for surveying.

Because GPS surveying uses multiple reference surfaces, the

desired reference surface must be specified.


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Difference in Elevation

A difference in elevation isthe vertical distance

between two level surfaces

or planes.

When the elevation of each of the level surface or plane is known,

the difference in elevation can be calculated between the earth and

any level surface or plane.

The difference in elevation can also be determined between any twosurfaces.


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Backsight

Def: A back sight is a rod reading taken on a point of known, orassumed elevation.

Backsights areusually used toestablish the height

of the instrument.

Instrument height = Elevation + Rod reading


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Foresight

A foresight is a rod reading taken on a point with unknown elevation.

It is used to determine the elevation.

Elevation can beactual or relative.

Elevation = Instrument Height - Rod Reading


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True vs. Intermediate Foresights

In surveying two different types of foresights are used,

intermediate, and true.

An intermediate foresight is a rod reading on a point that will

not be used as a turning point or benchmark.

A true foresight is a rod reading on an point that will be usedfor a turning point or for a benchmark.


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Turning PointA turning point (TP) is a temporary benchmark.

The purpose of the turning point is to provide a continuousreference point for the height of the instrument when it is moved.

Because it is a temporary benchmark, a turning point must beestablished on an object with stable elevation.


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Facts About Turning Points

The turning point should be a stake or other durable structure.

If the turning point is not at the earths surface, the elevation of thatstation can not be used during design.

When the turning point is on the surface, the elevation can be used.

The TP becomes a new point that can be used as a reference point.

Turning points are intended to be temporary. Only used during the

life of the survey.


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Balancing the Sights

Balancing the sights refers to setting the instrument 1/2 waybetween the two stations.

This reduces the chance of the error that occurs if the instrumentis not level.


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Unbalanced Sights

If the instrument is not level,

the rod readings will beincorrect.

In the illustration the readingwill be greater than it shouldbe.

An error will also occurwhen the instrument isrotated to the second sight.Because the instrument is agreater distance from therod, the error will begreater.

Error

1{ Error

2


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Balancing Sights-cont.

When the distance from the instrument to the rod are the same forboth shots, the errors cancel each other.

A error also occurs whenthe instrument is rotated totake the next shot.

The rod reading will belonger than it should be.

In this example because theinstrument is not level, the rodreading would be shorter thanit should be.


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Fin

principios de medidas topograficas

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