Control surveys establish precise horizontal and vertical relationships of a network of monuments/markers which serve as the coordinate basis for subordinate surveys. Examples of survey projects utilizing this type of control are Plantsite Control, Deformation Monitoring, Aerial, Topographic, Mapping or any other survey requiring the establishment of a set of control points to be used on an ongoing basis for additional surveys.
In order to formulate a survey methodology for any Control Survey, the Alberta Land Surveyor needs to have an understanding of the project and expectations of the end user. The required accuracy of the positions to be determined, the duration of the project, the proposed use of the positional data, the need for inter-visibility of control points all important. The design of the control survey network requires the consideration of these items together with survey instrumentation to be used, the geometry of the proposed network, observation types, potential environmental influences and monumentation to be placed.
The monumentation used must be appropriate, secure, and stable. Consideration of soil conditions, physical placement, stability concerns and cost of installation will assist in determining a suitable monument configuration. Various types are available.
All survey equipment used must be in adjusted working order with appropriate calibration completed prior to commencing any measurements. Equipment techniques and procedures must also be considered. Survey equipment used could include GPS ( Static or Kinematic ), conventional survey equipment such as total stations or precise leveling equipment or a combination thereof.
Observation procedures should be standardized and established prior to commencement of the survey. These procedures should also consider the environmental factors encountered during the survey. Quality assurance procedures must be followed to confirm the expected results.
Processing of the measurement data would generally be through a network adjustment utilizing a practical observation weighting scheme through least sqaures. A final report documenting the 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.
The control survey requirements are not, in general, covered by any statutory or regulatory requirement. Some components are referenced in the Alberta Land Surveyors’ Manual of Standard Practice, however, the Alberta Land Surveyor will be able to advise you on the appropriate survey parameters for your project.
Further references include the following:
Specifications and Recommendations for Control Surveys and Survey Markers, Specification Series 1978
Energy, Mines & Resources Canada, Ottawa, Canada
Analysis and Adjustment of Survey Measurements
Edward M. Mikhail, Ph.D. and Gordon Gracie, Ph.D.