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Summary Of GEOMATICS ENGINEERING / SURVEYING CHAPTER 1

Summary Of GEOMATICS ENGINEERING / SURVEYING
CHAPTER 1

BY:Islam Ahmed Ali

Geomatics: It is the discipline of gathering, storing, processing, and spatial information.

Surveying: The discipline include all methods of gathering and processing information about our physical earth and its environment.

Geodesy: is the discipline that deals with the measurements and representation of the Earth, including its gravity field, in a three-dimensional time varying space.

The role of Surveying and what Surveyors are needed:

  • to keep the geometric order during the construction process
  • to provide fundamental data for the design and planning process
  • to provide quantity control during the construction process
  • to observe the structure after the construction

Surveying activities during the construction process:

-Before Construction:

  • Planning and data collection
  • Observations in the field
  • Processing the observations (office)
  • Drawing maps, plans or providing numerical data
  • Presenting documentation to the client
    -Under Construction
    :
  • Setting out on each step of construction
  • Field checks of construction
  • Providing data and services to the client
    -After Construction
    :
  • Final plan on the construction
  • Presenting documentation to the client
  • Deformation Monitoring, Load Tests

 

 

Primary Classification of Surveying:

1- Plane Surveying

2- Geodetic Surveying

Plane Surveying:

  • small areas (areas < 250 Km2)
  • Surface of earth can supposed to be flat
  • Measurements plotted represent a horizontal projection of the actual field measurements
  • All Z dimensions are referenced to the mean surface of the earth or MSL:
                 Plane surface
                 Plane triangle
                 Plane angles
  • most engineering surveys are classed as plane surveys

Geodetic Surveying:

  • Large areas
  • Surface of the Earth can not supposed to be flat
  • the curvature of the Earth is taken into account
  • Curved line
  • Spherical triangle
  • Spherical angles
  • Mostly used for establishing control networks, determining the size and shape of the Earth and determining the gravity field of the Earth.

Secondary Classification of Surveying:

  • Based on instruments
  • Based on methods
  • Based on object
  • Based on nature of field

 

Based on methods:

  • Triangulation surveying
  • Traverse surveying

Based on object:

  • Geological surveying
  • Mine surveying
  • Archeological surveying
  • Military surveying

Based on nature of field:

  • Land surveying
  • Marine surveying
  • Astronomical surveying

Types of Land Surveying:

  • Cadastral Surveying (المسح العقاري)
  • Construction Surveying (مسح البناء)
  • Topographic Surveying
  • City Surveying
  • Hydrographic Surveying
  • Geodetic Surveying
  • Photogrammetric Surveying

Basic Principles of Surveying:

  • To work from whole to the part
  • To locate a new station by at least two measurements (linear or angular)

triangulation:

  • It is one of the methods of providing control in an area which is to be surveyed

Coordinate System can be 2D or 3D

Types of coordinate systems:

(1) Geographic coordinates (f, l, z)
(2) Global Cartesian coordinates (x, y, z): A system for the whole earth (3) Projected coordinates (x, y, z) on a local area of the earth’s surface

– The most widely used global coordinate system consists of lines of geographic latitude (phi) and longitude (lambda)

– Lines of equal latitude are called parallels.

– Lines of equal longitude are called meridians

The equator is the largest circle and divides the earth in half

prime meridian: is the line of longitude that passes through Greenwich England

  • The latitude of a point P is the angle between the ellipsoidal normal through P and the equatorial plane.
  • Latitude is zero on the equator (0 °)
  • Latitude is increases towards the two poles to maximum values +90 (90 °N) at the North Pole and – 90 ° (90 °S) at the South Pole

The longitude ( λ ) is the angle between prime meridian ellipse and the meridian ellipse containing the point P.

  • The longitude is measured in the equatorial plane from the meridian of Greenwich ( λ = 0 ° ) either eastwards through λ = + 180 ° (180 °E) or westwards through λ = – 180 ° (180 °W) .
  • 3D geographic coordinates (f, l, z) are obtained by introducing the ellipsoidal height z to the system

A map projection is the systematic transformation of locations on the earth (latitude/longitude) to planar coordinates

Methods of Expressing Scale:

  • IN WORDS
  • BY REPRESENTATIVE FRACTION
  • BY SCALE LINE

 

Sources of errors:

  • Natural causes
  • Instrumental imperfections
  • Personal limitations

Types of errors:

  • Systematic or cumulative
  • Accidental, random or compensating

Systematic errors can be calculated and proper corrections are applied to the observation.

Accuracy is the nearness of the measurements to the “true value” of quantity being measured.

Precision  refers to the closeness with which the measurements agree with each other.

 

Summary Of GEOMATICS ENGINEERING / SURVEYING
CHAPTER 1

BY:Islam Ahmed Ali

اظهر المزيد

Islam Ahmed

إسلام أحمد، هو شاعر ومبرمج وممثل مسرحي ولد في جمهورية مصر العربية و عاش و ترعرع في سلطنة عمان , طالب جامعي بكلية الهندسة ومؤسس شركة أنجز ويب لخدمات الويب المتكاملة ومؤسس منتديات العرب أشقاء سابقا ومجلة أنجز ويب حاليا.

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