Control surveys establish precise horizontal and vertical relationships of a network of monuments/markers which serve as the coordinate basis for additional surveys or

Constrol survey provides a framework of survey points, whose relative positions, in 2D or 3D, are known to specified degrees of accuracy

Project that require control surveys;

1. Topographic survey and large-scale planning
2. Civil engineering & construction works
3. Deformation surveys for all manner of structures
4. Extension and densification of existing control networks

Requirements for network design of the control survey;

• understand the project e.g. duration
• Understand the expectations of the end user
• Required accuracy of the positions to be determined
• Proposed use of the positional data
• Inter-visibility of control points
• Survey instrumentation to be used
• Geometry of the proposed network
• Potential environmental influences and monumentation to be placed

Consideration of monumentation of controls;

• appropriate, secure, and stable,


• soil conditions,


• physical placement,


• stability concerns and,


• stability concerns and,

All survey equipment used must be in adjusted working order with appropriate calibration

Observation procedures should be standardized and established

Quality assurance procedures must be followed to confirm the expected results

Processing of the measurement data is generally done through a network adjustment utilizing a practical observation weighting scheme through least squares

Report; background of the project, initial scope of the project, project objects, the survey methodology utilized, the field measurements made, the analysis and results of the survey ( including accuracy statements) and conclusions/recommendations from the control survey

Survey equipments that can be utilized;

1. GNSS ( Static or Kinematic)


2. Conventional survey equipment such as
• total stations
• precise leveling equipment
• a combination

The methods used for control surveys are

1. Traversing (ray trace)


2. Intersection and resection


3. Least squares estimation of survey networks


4. Satellite position fixing

There 2 approaches; pre vs. post control surveys

Depend with the personal preferences

Project timeframe

Surveying with GNSS equipment has many advantages over conventional survey methods

1. It is not necessary to have inter-visibility between project control monuments
2. GNSS collection can be used at any time, day or night, and in most weather conditions
3. GNSS methods typically produce results with very high geodetic accuracy
4. On accomplishes more work,in less time with fewer people

Using GNSS equipment also has several disadvantages

1. GNSS receivers require a clear view to a minimum of four satellites
2. Satellite signals may be blocked or deflected by buildings, trees, utility poles, etc
3. GNSS cannot be used indoors and is difficult to use in urban environments, heavily wooded areas, or in mountainous terrain
4. The vertical component of GNSS measurements may not meet established collection standards for features with critical elevation accuracies

A static network is made up of multiple GNSS receivers collecting data over multiple GNSS sessions

Static observations typically range from 30 to 120 minutes depending on the distance

The data from these observations are post-processed with proprietary GNSS software using the least-squares method of adjustment

The longest baseline in the GNSS session is used to determine the collection time

• As a rule of thumb two minutes of collection time is needed for each kilometer of baseline length
• e.g. 10 km = 20 minutes collection time

Real-time kinematic (RTK) method is a radial survey that utilizes two or more GNSS receivers

RTK method does not require the data to be post-processed; thereby allows the user to obtain coordinates in real-time

RTK method measure baselines from the base station to the rover by a radio data link

What is RTK Initialization? & why is it important?

What is Site calibration/Localization? & why is it important?

Reference data sources - CORs

1. NGS https://geodesy.noaa.gov/index.shtml click here or https://www.ngs.noaa.gov/OPUS/ click here
2. AFREF http://afrefdata.org/ click here

Conventional surveying methods;

Traversing/Resection with traverse adjustment

• Method 1 - measurements are taken from at least two existing control points to each extendible control point

Conventional surveying methods;

Traversing/Resection with traverse adjustment

• Method 2 - a sub-traverse is run from an existing control point through all of the extendible control points to another existing project control point

Conventional surveying methods;

Traversing/Resection with traverse adjustment

• Method 2 - a sub-traverse is run from an existing control point through all of the extendible control points to another existing project control point

Conventional surveying methods;

Traversing/Resection with traverse adjustment

• Method 3 - a resection is performed using two existing control points for each extendible control point

Assignment 3

• Request LAB for static rinex data & performed post-processing using the following software: bernese, GAMIT/GLOBK, Compass etc.

Queries about this Session, please send them to: jmwaura@jkuat.ac.ke

*References*

• American Society of Civil Engineers, 2000
• The surveying handbook. 2nd Edition. Springer, 1995, Brinker, R. C. and Minnick, R.
• Kenya Survey Manual SOK
• Land Surveyor Reference Manual Andrew L. Harbin