Often overlooked but critical to the smooth running of any project is the integrity of its survey control network. Typically, such networks are established by the owner early in the design process and are initially used for the data acquisition phase of the project. For a number of reasons, including the impact of construction, these networks are generally inadequate to support operations from beginning to end. Often a contractor will just start performing layout from pairs of these points without adequate testing and, as the project proceeds, subsequent generations of control get weaker and weaker. Depending on the nature of the construction, this can lead to serious problems when the "pieces of the puzzle" fail to fit together properly.
Among our tasks on a number of projects has been the planning and oversight of control network testing and densification. Our process generally involves setting up a network that engages all of the "monuments of record" for the project and adds many more that are positioned to be easily visible but safe from construction operations. Recognizing that no control network is perfect and that some points might be in error, our densification always employs a rigorous least-squares analysis that allows us to test the integrity of record points and properly weight them in the final adjustment. This also allows us to take into account the geodetic effects that often must be considered on large-scale projects.
The result is a network that respects the intended frame of reference and preserves it throughout
the construction process.
