There are dozens of different types of land surveys, each showing different elements of the land. One type of land survey is a deformation survey.
What is it?
Deformation surveys are used to measure whether or not a specific area of land or object is moving or changing shape. A deformation survey shows a change in measurements and alterations of shapes and dimensions of the land.
Deformation can be caused by a variety of stresses – both natural and man-made. This can include landslides, earthquakes, sinkholes and man-made structures.
Surveys are important for a variety of reasons. They are an essential part of risk and hazard management on both a small and large scale.
Deformation surveys are very important in areas prone to earthquakes as these areas are prone to land deformation, which can have detrimental effects on land and buildings if it is not monitored adequately.
Insurance premiums can be decreased significantly through regular deformation surveys on property, as they help to reduce risk exposure both before and during construction and during the lifespan of the property.
When are they used for?
There are a variety of purposes for these surveys. They are most commonly used in civil engineering applications such as the building and monitoring of dams, tunnels, roads, bridges and viaducts.
Owners of high-rise and historical buildings also need to regularly have a deformation survey conducted for their buildings to check that there are no current or potential structural damages.
They are also used prior to building on land – particularly in earthquake prone areas and along volcano and landslide slopes. It is important to assess the stability of land before construction starts.
How is deformation surveyed?
There are several methods to creating a survey. However, the general method is to measure the land at one stage in time then measure it again at a later date and then compare the two to see if here are any changes.
There are three main devices used to make a deformation survey: geodetic measuring devices, such as total stations, levels and GPS receivers; geotechnical measuring devices, such as rain gauges, thermometers, barometers, tilt meters, accelerometers, piezometers and extensometers; and radar measuring devices. Deformation surveyors may use one or several of these devices to put together a deformation survey.
How often should surveys be done?
To be able to assess whether land is moving or changing several deformation surveys need to be done over time to track the changes.
The regularity of deformation surveys depends on the specific application. In some cases deformation surveys need to be done both in the short term and over a longer period. For example, the land supporting the Golden Gate Bridge in San Francisco may see movements every few seconds due to traffic – but these changes are a lot different to the changes seen due to tectonic activity over months and years.
Where to find a deformation land surveyor
Deformation land surveyors are easy to find. The internet is a great resource, and there are many websites that list land surveyors in your local area. You can also use the internet to get references and reviews of specific land surveyors.
Be sure to choose a land surveyor that has experience working with deformation surveys and ask for references and examples of similar previous work they have completed. Get several price quotes before settling on a land surveyor.
Always check that your land surveyor is licensed to work in your state and has all the credentials that are required.