What is surveying?
The art, science and technology of collecting,
processing, management and visualization of
geospatial data and information
Why is surveying important?
- Legalizing land ownership
- Construction of engineering facilities & infrastructure
- Exploitation of mineral resources
- Positioning and navigation
- Mapping
What are the branches of surveying? (13)
- Geodetic surveys
- Engineering Surveying
- Topographic surveying
- Cadastral surveying
- Mining Surveying
- Satellite - Global Navigation Satellite Systems (GNSS)
- Inertial Surveying
- Hydrographic Mapping
- Photogrammetry
- Remote Sensing
- Geographic Information Systems (GIS)
- Land Information Systems (LIS)
- Cartography
What are the basic principles of surveying?
- Working from the ‘whole to the part’ - from higher accuracy to lower accuracy methods
- Always perform independent checks
- Specifications and accuracy is required
What are the classifications of surveys?
- Plane Surveying
- Geodetic Surveying
What is plane surveying?
The horizontal plane is used as the computational reference, with the vertical direction considered constant.
All angles measured are plane angles.
Involves areas of limited size with the assumption that the earth’s surface is flat.
What is geodetic surveying?
The curved earth’s surface is used as the computational reference, with the vertical direction changing.
Earth is modeled with two semi-axes (radii): a and b
Involves large areas of the earth’s surface, with the earth’s curvature considered
What are the types of survey measurements?
- Linear
- Angular
Describe the linear measurements?
- Horizontal distances:
Measured directly by tape/steel band/ or indirectly by total station - Slope distances
Measured directly by EDM in a total station - Vertical/height differences
measured directly by level or indirectly by total station
Describe the angular measurements?
- Vertical/elevation angle
angle to a point with respect to the 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
Survey instrumentation for:
1. Height difference measurement
2. Distance measurement
3. Angular measurement
4. Angle and distance measurement
5. Other
- Height difference measurement
- Dumpy
- tilting
- automatic
- digital
- laser levels
- total station
- barometer
- gravimeter
- GPS - Distance measurement
- Steel band (chain)
- Nylon tape;
- Electronic distance measurement (EDM). - Angular measurement
- Theodolite, electronic theodolite. - Angle and distance measurement
- Total station combines EDM and
electronic theodolite. - Other
- GNSS
- Inertial Measurement Unit (IMU)
- Photogrammetric Stereoplotters
- Laser scanner/LiDAR
What are functions of the following survey instrumentations?
- Steel tape
- Clinometer
- Compass
- Automatic level and staff
- Theodolite
- Total Stations and prisms
7.Optical square - Digital level
- Photogrammetric stereoplotters
- Laser scanners/LiDAR
- Steel tape
measures short distances on engineering site - Clinometer
measures angles of elevation/depression between users eyes and observed point - Compass
measures relative magnetic bearings - Automatic level and staff
measures backsights, foresights and intermediate sights by manual observations - Theodelite
measures horizontal and vertical angles - Total Stations and prisms
used for automatic logging of horizontal and vertical angles and electronic distance measurement
7.Optical square
used to set out points at right angles to occupied point on alignment
- Digital level
automates functions of automatic level using CCD array and detection algorithm - Photogrammetric stereoplotters
restores aerial photographs & plotting topographic maps - Laser scanners/LiDAR
3D mapping with sensor based on pulses towards object and measuring the range from point cloud
Integration of technologies in mobile mapping
- Remote sensing
- GNSS
- IMU
- Mobile phone
- Internet
- GIS
Principles of field notes
- A permanent record of work
done in the field. - Must be thorough, neat, accurate
and guarded carefully. - All notations are recorded in
pencil. - Mistakes in field books are never
erased but crossed out with one
horizontal line through the middle. - Specific field note formats exist
for different types of surveys as
stipulated in the Surveyor’s Manual. - This is particularly important for
cadastral surveys, where notes may
be used as evidence in court cases.
Basic principles of survey practice are:
- Complete in shortest possible time.
- Complete at the least possible cost.
- Complete according to client instruction(s) and survey manual specifications.
- Complete using instrumentation of appropriate accuracy.
- Ensure safety is maintained.
- Consider ROI of using a mapping system/survey instrument against another
Define precision and accuracy
Accuracy is how close a measurement/observation is to the true and accepted value.
Precision refers to the degree of closeness that measurements/observations of the same item are to each other.
Sources of errors
- Natural
due to the medium in which observations are made
factors: wind, temperature, humidity - Instrumental
due to imperfections in instrument construction/adjustment
reduced by calibration/observation - Personal
limitation in operator ability
improved with practice
Types of errors
- Mistakes/gross errors/blunders
Often large magnitude - Systematic/deterministic errors
error that follows some physical /geometric law
can be corrected - Random/accidental errors
errors that can’t be modelled and corrected
governed by probabilistic/stochastic models
