Delivering Precise Mine Location, Documentation and Clearance with Trimble GPS Technology   

Using a Trimble Tablet Starup photographs and records the position data of a detonator with a firing pin found during the excavation work.

No company knows this better than Damasec, Denmark's leading company for mine clearance. The Danish Ministry of Transport and the Danish Coastal Authority selected Damasec, and civil contractor J. Jensen A/S, to clear the country's remaining mine fields left from World War II. The Skallingen mines were laid by the German occupation force in 1944 as part of the Atlantic Wall.

Although the majority of the Skallingen peninsula was cleared after the war, there was an area of approximately 2.5 square kilometers which was not cleared, and it remained fenced and restricted from public use.

In 2006 the Skallingen project was devised, a contract tender was issued and it was subsequently divided into three phases. The first included clearing mines and explosive materials from the Skallingen beach and sand dunes at three, first priority locations. This area spanned approximately 19 hectares. The second phase involved the clearance of priority two areas, which included approximately 47 hectares of beach and dunes; phase two of this project was complete in 2007 and 2008. The third stage of the Skallingen mine project covers an area of more than 123 hectares and is comprised of marshland, dunes, dike and beach. According to Peter Starup, project leader and GIS manager for Damasec, during phase three there is a total of 270, 000 cubic meters of sand that will be screened for mines and mine remnants.

Damasec and J. Jensen A/S selected Trimble technology for a complete system that provides accurate location data and the ability to complete real-time field calculations. In addition, the team was looking for a solution that provided project workflow software for seamless data transfer between the field and the office.

Armored excavators equipped with Trimble 3D Grade Control Systems.

The 30 ton excavators and dozers used on the Skallingen project are equipped with 3D Trimble® GCS900 Grade Control Systems. The grade control systems use GNSS receivers which are able to use satellite signals from both GPS and GLONASS satellites for increased coverage. In addition, Trimble Site Positioning Systems are being used to provide accurate site measurement and stakeout capabilities.

At the start of the project, Starup and the Damasec team created precise 3D digital designs of the Skallingen area. These drawings were created to give machine operators the ability to dig to specific depths in the dune area, using excavators and dozers. Design simulations in 3D make it possible for managers, GIS specialists and machine operators to check the data before they leave the office. As users drive a virtual machine over the design in the Trimble office software, the system illustrates elevation levels as they would appear in the machine on the job site.

Starup reviews graphic images of an excavated mine area.

The mine clearance location spans the North Sea dike and includes low and the high marshland areas. Due to the complexity of the project and environmental factors, the team's designs were adjusted and updated often to reflect on-the-ground conditions. Subsequent terrain analysis also resulted in the size of the suspected mine area to increase slightly. As a result the volume of material to be excavated also increased because the identified mines are buried deeper than originally anticipated. With the Trimble grade control technology, operators can see in real time exactly how deep they have to excavate in different mine areas. At the end of each day, data is transferred from the machines, and using the Trimble office software team members can obtain digital elevation model of the excavated area.

GIS Manager Peter Starup surveying a small schutz mine and behind him a larger stock mine is visible.

"When we uncover a mine it is located and measured using the Trimble Site Positioning System rover (which includes the GNSS Smart Antenna and Trimble Tablet field computer)," said Starup. "With this system we can record the position accurately, indicate whether the mine is to be exploded using an in-situ leaching process, whether it is to be moved and exploded, or whether it can be removed. Finally we take a georeferenced photograph with the Trimble Tablet so that there is an automatic link between the measured position of the mine and the corresponding entered data; all the data from the field is then collected and reviewed."

At the end of the day, Starup reviews the information about each identified mine in order to determine whether or not to backfill the excavation. If a mine was located near the designed excavation depth, he may then instruct the machine operator to dig deeper as a precaution, in case there are more mines to uncover. Using this method, Starup and his team have found mines at depths and in places which were not anticipated.

While the total number of mines in the area is not known precisely, so far approximately 150 potentially operational anti-tank and anti-personnel mines have been found down to a depth of four meters.

In addition to using Trimble Grade Control and Site Positioning Systems, Damasec and J. Jensen A/S are also using the Connected Community. The Connected Community is a secure web based data sharing system that allows contractors to manage project data such as designs, plans and reports and allows controlled, secure access to specified users. Team members are also notified via email when information is revised or added.

"This means that the customer and the various parties involved in the project are able to see all the files, conference reports, calendar information, facts on the status of the project, documentation, quality assurance records, photographs and surveys, and more," said Starup. "It is a very powerful, practical tool which enables the customer to monitor the development of the project closely. It is simple to use and protects the data because they are on a server rather than an individual machine."

The team is also using Business Center - HCE software from Trimble to manage, analyze and process all field survey data, including data from total stations and GNSS receivers. Engineers calculate the volume of excavated material and they are able to visualize in 3D the completed work. Starup believes this is an important benefit because the system empowers his team to deliver extremely accurate documentation outlining the work they have completed, compared to project specs and contract requirements.

Project managers are leading efforts to rehabilitate the Skallingen peninsula, minimizing scaring from mine removal and working with ecologists to restore native wildlife and ecosystems to the area. Before excavation started, the original ground was measured by means of GPS. The data was loaded onto the in cab control box to provide the operator with information for rehabilitating the area so that the dunes, dike and marshlands are restored.

Once the Skallingen project is complete, leaders estimate the safe removal of nearly 500 unexploded mines. Starup believes Trimble technology is a critical component to ensuring the success of this project and in supporting Denmark's compliance with the UN Ottawa Convention for the removal of anti-personnel mines.

"All in all Trimble systems mean that we have very accurate documentation on what we have done on the site, in the form of positions, heights, graphic images and photographs and we can share this both internally within the consortium and with our client via the Connected Community," said Starup. "It makes cooperation easier when everything is so well documented; we do not need to discuss the scope of tasks and whether everything was completed. It is hard to imagine trying to do this project without Trimble."