Deformation Survey: a survey to determine if a structure or object is changing shape or moving. The three-dimensional positions of specific points on an object are determined, a period of time is allowed to pass, these positions are then re-measured and calculated, and a comparison between the two sets of positions is made.
Bringing more than 30 years of experience to Deformation Surveys, Terrasurv offers a variety of services to monitor structures and the environment:
Man made structures are subject to external loads that cause deformation of the structure itself as well as unwanted displacements of the structure and its foundations. This can often be a threat to life and property.
Mining and construction activity can cause changes in the ground surface as well as to structures. Surface subsidence can cause catastrophic damage. Monitoring can be done using GNSS Satellite Surveying, Total Stations, and Precise Differential Leveling.
Dam Deformation: The Pittsburgh District of the US Army Corps of Engineers owns and operates 23 navigation Locks and Dams on the Allegheny, Monongahela, and Ohio Rivers as well as 16 Flood Control Dams. Since 2005 Terrasurv has been performing annual and semi-annual deformation surveys at these projects. Each of the 39 projects were visited in 2005 to analyze the existing deformation networks at each project. Least Squares simulations were then used to design an observation scheme at each that would meet specified target horizontal accuracies of 3 mm for concrete structures and 2 cm for earthen embankment dams. Each periodic survey consists of taking high accuracy total station measurements (concrete) or GNSS surveys (earthen dams), processing and adjusting the data, and presenting the results in a comprehensive report.
A typical monitoring project consists of a site visit to determine existing conditions and to plan the network. This information is then used in the office to plan a scheme of observations that will meet the required accuracy. Next, the field observations are performed. This data is then processed and adjusted in the office to yield data that can be used as a baseline for future observations or to compare against previous surveys.