Advances in Ground Monitoring Techniques – A Surveyors Perspective

In essence ‘Surveying’ is simply the science of measuring positions on Earth. Surveying has been a key element in the development of the human environment since we stepped out of the caves. The relationship between surveying and geotechnical engineering principles arguably dates back just as far. There is a real synergy between these disciplines / professions that, in the main, is often not fully appreciated.

The core mathematical foundations upon which surveying is based are essentially unchanged. What has changed enormously over the centuries and dramatically over the past decade or two are the technologies available to Surveyors to aid them in measuring the ‘Earth’, and anything built on / in it.

This paper touches on a range of current survey measurement methodologies, some of which may be considered ‘tried and true’ traditional techniques along with a number of exciting newer technologies such as LiDAR (Light Distance and Ranging), DInSAR (Differential Interferometric Synthetic Aperture Radar), GNSS* (Global Navigation Satellite System) based real-time 3D measurements, with particular attention given to drone (Unmanned Aerial Vehicle – UAV) based digital photogrammetry.

Like many measurement techniques, digital photogrammetry is a technological evolution of a well understood and developed traditional analogue approach. With the advent of laser scanning (LiDAR) measurement technologies in the late 1990’s, analogue photogrammetry rapidly fell out of favour for all but a few niche measurement applications. However, over the past few years there has been a dramatic shift back to ‘digital’ photogrammetry. This re-emergence has been facilitated by advances in digital photogrammetry autocorrelation algorithms, increases in computing power, relatively affordable PC based software solutions, digital SLR cameras and most recently, the development of commercially available drone (UAV) based digital camera systems. Modern digital photogrammetry solutions are now capable of very quickly capturing high resolution, high accuracy and generally high quality measurements with flexible outputs ideally suited to 3D surface modelling and measurement problems. These technical attributes in tandem with affordable digital cameras and modern UAV platforms has opened up a wide range of applications, many of which are in mining, engineering and monitoring fields.

More important than any particular measurement technology, effective survey monitoring, or any type of monitoring, starts with clearly understanding: what has to be measured (critical parameter(s)), how accurately it needs to be measured, and at what frequency are the measurements required? Only once these factors are crystal clear should we start to consider which technology or combination of measurement techniques is most suitable for the project. In many cases, an integrated approach utilizing a blend of ‘surveying’ and ‘geotechnical’ measurements will deliver the optimal monitoring strategy.