Load & Haul

Meeting the challenges of surveying technology

Survey instrumentation available in the mid-20th century relied on excellent optics. Trigonometry was the foundation of surveying, using the measurement of both horizontal and vertical angles to give an angular difference between points and to derive a distance. Recording data, even into the 1980s, was done by hand and plans drawn manually. Instruments were built to last. The iconic Wild T2 went into production in 1924 and continued to be made until 1991. Surveying was exciting and pioneering, concerned with building bilby towers to get above the jungle canopy and astro-navigation to fix a position in the desert.

The development of electronic distance measurement (EDM) was revolutionary. The transmission of an infrared beam and its reflection back by a prism to give a direct measurement of distance was initially an add-on module. However, when it became fully integrated into the theodolite, the term “total station” was born. At the same time, on-board logging allowed the reliable collection of more data and relieved the surveyor of the elusive hunt for transposed numbers.

In the 1990s, total stations became robotic, the prism being automatically tracked and controlled from a remote radio on the pole. The assistant, who formerly served an apprenticeship behind the instrument, was freed to work productively and learn alongside the surveyor. The integration of a laser meant inaccessible areas could be surveyed remotely.


{{image2-a:r-w:250}}An enduring problem for the surveyor was how to fit the survey into real world co-ordinates. In the mining and quarrying industries arbitrary co-ordinate systems were not an option because everything had to be fitted to the national grid. To traverse in from trig pillars was the ultimate solution but in most cases the fit to Ordnance Survey (OS) maps was achieved by picking up and best fitting (graphically) points of local detail. In rural areas, this would often mean fence corners, and although the OS is comprehensive, inaccuracies in the order of metres are common.

The development of global positioning systems (GPS) solved this key issue. Early systems were huge, heavy and required many hours of observation time to get one (post-processed) co-ordinate. GPS receivers calculating a position essentially by measuring accurate distances to satellites in an orbit 20,200km from the Earth are really impressive but struggle with ionospheric distortion of the signals. This is resolvable by using a second receiver fairly close by, to collect the same signals and transmit the corrections to the surveyor. Hence, differential GPS to centimetric accuracy.

{{image3-a:r-w:250}}At first the surveyor would have his own differential system, consisting of two GPS receivers acting as a base and rover. The base, if set up over a known point, would allow surveying directly to the chosen co-ordinate system, hence real time kinematic (RTK) surveying was born. If the corrections could be broadcast over the phone system, a local base station would no longer be necessary, freeing surveyors to work without constraint. However, a trial by the OS in the 1980s generated a massive phone bill and a lot of red faces. For many years, progress had to wait for low cost mobile phones and the internet to catch up.

Today, via mobile phones, surveyors around the world can pick up corrections from national virtual GPS networks over the internet, straight out of the car and immediately working on a national grid.

GPS remains and will continue to remain the primary means of positioning on the world’s surface. The network solutions are reliable, stable and very accurate. No markers are required on-site and survey control is a breeze.

GPS did, however, give quarry surveyors a headache around the issue of scale factor.

{{image4-a:r-w:250}}In the days of total stations and small quarries, many surveyors based their mapping on a simple “earth is flat” system, but GPS forced us all to accept it is, in fact, a sphere (well, almost) and mapping has to accommodate to this (in the UK via the Transverse Mercator Projection). Close to the central meridian this is not too much of a problem but further east and west of Greenwich and with quarries of more than 1km in length, distances on the ground could be markedly different from those on plan. Many companies used this as an opportunity to shift and stretch their mapping to standardise on the OS co-ordinate system.

The headache for quarry surveyors was nothing compared with that now faced by the OS itself, which knew the Earth was round but suddenly found there were errors in the primary control network on which all national mapping was based, sometimes in the order of tens of metres. Hence, the 1990s rectification program. Now with everything sorted, beloved trig pillars and benchmarks finally became redundant.


{{image5-a:r-w:250}}The emergence of high definition scanning initiated the challenges we still face today. It is now possible to takes thousands of readings per second. As surveyors, our role now is to filter and manipulate this data so it is suitable to the multiple disciplines that require spatial data for the design and management of quarries. At the turn of the 21st century, led by the Royal Institute of Chartered Surveyors, surveyors’ job titles changed. They were no longer land surveyors (collecting spatial data) but geomatics professionals responsible for the collection, manipulation and presentation of spatial data (albeit still with muddy boots).

The past few years have seen a huge refocus on photogrammetry. Age-old technology has been given new life by high resolution but inexpensive digital cameras teamed with powerful software that can recognise and match identical points in overlapping photographs, to derive an accurate point in 3D space with an attached RGB value. The resultant point cloud, although similar to LiDAR data, is presented in full colour.

The new kid on the block, of course, is the unmanned aerial vehicle (UAV). The largest annual world exhibition for geomatics (Intergeo in Germany) has been packed for years as UAVs explode onto the market. A recent report from the UK’s House of Lords cited a prediction of the creation of 150,000 jobs within the European UAV sector by 2050. This is certainly achievable if the current UAV innovation, production and application continues to grow with its current force.

{{image6-a:r-w:250}}What is perhaps most interesting for surveyors is the investment and commitment of survey equipment manufacturers to the most professional (and expensive) commercial systems on the market, alongside UAV manufacturers recognising that surveying is a key mainstream market, rather than a niche specialty.

Leading the way are Trimble with the acquisition of Gatewing and Hexagon with Aibotix. Both systems sell for about 50,000 euros ($AUD75,448). The BBC, by way of comparison, is using £800 ($AUD1706) UAVs for filming.

A UAV is, of course, just a platform for putting a sensor in the sky. For quarrying, this is crucial, allowing the sensor to “see” all the detail the operator wants to survey, and to do that remotely, addressing one of the key health and safety issues of the industry – removing personnel from working areas.

The UAV industry is driving developments in sensors that will bring benefits to the quarrying sector. It is already possible to equip UAVs with LiDAR, GPR, multi- and hyper-spectral sensors (with potential applications for geotechnics). From a photogrammetric viewpoint, the UAV is able to fly with an accurately planned overlap and geotag the photography with an increasingly accurate camera position. Three-dimensional accuracy for the point cloud is now better than GPS.

{{image7-a:r-w:250}}Alongside UAVs is mobile mapping, a vehicle-based system that integrates GPS, high definition scanning, inertial systems and, increasingly, photogrammetry for extremely rapid data collection and processing at high vehicle speed.

All this exciting technology is about collecting point clouds, using them to generate accurate, rendered 3D models and ortho-rectified photographs. The problem is the quarrying industry is used to, and far more comfortable with, conventional data sets, eg polylines in CAD systems that act as breaklines in 3D models, and tadpoles on slopes. There is software that can auto-extract lines from clouds but while this works well with building elevations and even trees, quarries have few really well defined geometrical lines. Faces do not have sharp edges but roll over, and this is very difficult to cope with.


The future is for us all to work on and realise the potential applications for the rich, accurate and comprehensive virtual reality that surveyors today are capturing. As a profession, surveyors have always been frustrated about holding back a large part of the spatial data they have collected, from the time when levels were taken off paper plans to prevent overwriting. Finally the days are coming when it can all be shared.

A glimpse of the future can be seen in the strategic vision of companies such as Hexagon Mining, which see constant measurement and monitoring as the key to the most efficient and cost-effective use of mobile plant in particular, massively reducing fuel costs. At the heart of their vision is a real time, accurate virtual 3D model of the mine or quarry. Perhaps the spatial data will be collected and processed live by the site’s own mobile plant or fully automated intelligent UAVs, but there will still be a role for the land surveyor in there somewhere.

Simon Briggs is the managing director of UK geomatics solutions provider Geodime.
This article first appeared in the April 2015 issue of Quarry Management (UK) and is reproduced in Quarry with kind permission.

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