1. Chapter 1: Precision Survey Properties and Techniques
Chapter 1: High-Precision Survey Properties
Chapter 1: Precision Survey Properties and Techniques By
John Ogundare, Ph.D.

2. Chapter Objectives Be able to perform the following:
Explain the main properties of precision survey procedure with respect to basic survey procedure
Discuss the properties of the main classes of precision surveys
Explain different traditional measurement techniques used in precision surveys
Discuss the uses of different computation models for precision surveys
Discuss the technology progress in geodetic surveying equipment
Evaluate some safety issues to precision survey projects

3. Properties of Precision Surveys
Precision surveying - application of appropriate field of surveying to a project to achieve a desired accuracy (or precision)
Significant properties:
Precise and expensive instrumentations are used – typical tolerance or accuracy is up to 0.1 mm or better
Stricter observations and data handling methods (increased time, effort & costs) are required
Larger number of observations are collected – redundancy is important in assessing accuracy and reliability of results
More rigorous mathematical treatment for error evaluation is required

4. Qualification of Precision Surveyor
Understand intended use of survey measurements
Sources of errors in measurements – error budgeting
Design of survey scheme – appropriate instrumentation
Field survey procedures to minimize errors
Rigorous adjustment & analysis of measurements

5. Classes of Precision Surveys
Geodetic control network surveys
Monitoring and deformation surveys
Geodetic engineering surveys
Industrial metrology
Surveys for research and education (scientific applications such as in geodynamics)

6. Geodetic Control Network Surveys
Surveys which consider the true shape and size of the earth (e.g., ellipsoidal model, not a plane model) – conducted over large area
Establishes horizontal and vertical control points (absolute positions known) to support:
Basic framework (e.g., CSRS, NSRS, ESRS) for a country – useful as reference for topographic mapping, boundary demarcation, mapping natural resources, etc.
Engineering and construction projects (bridges, dams, tunnels, highways, pipelines, etc.)
Reference for positioning marine construction vessels (dredging)
Reference for monitoring and evaluating deformations of large extent (tectonic plate, land slide, etc.)

7. Geodetic Control Network Surveys: Models
Computation model:
True shape of the earth (e.g. ellipsoid) is considered
Absolute three-, two- or one-dimensional positions of points are determined

8. Monitoring and Deformation Surveys
Essential for understanding natural phenomena (earthquakes, land slides, crustal movement) and behavior of man-made structures (dams, bridges, tunnels, building, etc.)
Compared with geodetic control surveys:
Computation model: Absolute position not of interest but relative is; three-, two-, one-dimensional relative positions of points are needed
Measurements between epochs must be made in similar atmospheric conditions and instruments used must be similar

9. Geodetic Engineering Surveys
Application of rigorous geodetic methods to control and support engineering projects:
Construction and maintenance of tunnels, bridges, hydroelectric power stations
Relative positional accuracies of 10 ppm or better required
Most first order national geodetic networks may be unsuitable because of distortions in national frame
Local coordinate system (unlike the national frame) is commonly used

10. Geodetic Engineering Surveys: Branches
Mining surveying – about rock stability control & protection
Land surveying – focusing on establishing boundary lines of real property ownerships
Computation model:
Local coordinate system and relative positioning
Plane earth surface model (plane local coordinate system requiring map projection) is used for computation
Unacceptable distortion is extended too much beyond the coordinate origin

11. Progress in Equipment: (TMPL) Project
Choosing appropriate route: from use of topo maps, GIS, Google Earth to LIDAR systems
Acquiring right-of-way: from use of theodolite & chains to total station equipment and GPS
Leveling to desired grades: differential leveling procedure still common, but faster instruments like digital levels compared with optical levels

12. Industrial Metrology (or Survey)
Uses precision measuring techniques for positioning and aligning industrial machinery and scientific apparatus, including:
Aligning components of large antennas (parabolic, flat, etc.)
Checking aircraft dimensional quality of the various sub-assemblies
Mapping submarine hull
Alignment of magnets of colliders and alignment of accelerator facilities
Setting up and aligning machines in the industries
In-situ calibration of industrial robots

13. Industrial Metrology: Model
Geodetic metrology: uses geodetic measuring techniques
Computation model: three-dimensional local coordinate system
Optical tooling (or optical alignment): extremely accurate measurements are made using jig transits, optical squares, aligning telescopes, optical micrometers, laser interferometry
Computation model: along lines or planes

14. Precision Geodetic Survey Techniques
Techniques require:
Using precision equipment (stretching performance to limit of accuracy) – Theodolites, EDMs, total stations, Levels, GNSS surveys
Using GNSS (such as GPS, GLONASS, Galileo, etc.):
Generally used for most horizontal control surveys and precise surveys
Conventional surveys used in local and isolated monitoring schemes
Selection of right GNSS receiver for a particular project is critical to success of a project
Receiver selection depends on:
Applications
Accuracy requirements
Signal processing requirement

15. GNSS Surveys: Receiver Quality
GNSS geodetic quality receivers used in precision surveys:
They can process both code and carrier phases
Carrier phase receivers can be single frequency of dual frequency; dual frequency types are recommended
When receivers are used with a remote one (in static differential mode), the receivers shall have accuracy of 5 mm or better on baselines less than 1 km
Processing software must be able to process broadcast and precise ephemerides.
A minimum of 2 receivers needed for a project; same antenna type for all receivers to minimize phase centre biases

16. Conventional Horizontal Positioning Techniques
Techniques include:
Triangulation, trilateration, combined triangulation and trilateration, traversing, intersection and differential leveling
Combined triangulation and trilateration survey techniques produce the strongest network of horizontal control –recommended for high-precision surveys
Tunnel surveys in mountainous areas will require combined triangulation and traverse surveys
Triangles of a triangulation or a trilateration network should contain angles greater than 15 - 25
Underground surveys are based on open traverses measured with theodolite, total station, EDM and gyroscopic instrument (e.g., GYROMAT 2000) to provide orientation
Intersection method is commonly used in 3D coordinating systems
Resection: used to determine position and height of instrument setup station when measurements are made to at least two known points- in free-stationing to minimize the effect of centering error on angles

17. Geodetic Vertical Positioning Techniques
Techniques include establishing elevations of points with reference to the geoid:
Providing vertical control points
Differential leveling as the precise leveling technique (for first- or special-order accuracy)
Standard deviation of less than 1 mm/km or better may be desired – using precision spirit levels with micrometer or digital levels and invar rods

18. Review of Some Safety Issues
Needed as part of every survey project
Crews are to conform to some design safety rules to allow them to perform their duties in a safe manner
Dedicated personnel should be assigned sole responsibility of managing and promoting safety of work crews:
Taking appropriate actions on safety issues
Creating safety awareness
Organizing regular safety meetings
Safety issues: recognizing hazards, taking precautions, operating equipment safely, first aid procedures, understanding safety precautions.