Support to Volume Estimation of Extracted Material on the Iron Ore Mine in Ouenza (Algeria)
ArcelorMittal today operates a number of iron ore mines around the world and will develop this branch further. Iron ore reserve estimation, mineral exploitation and monitoring performance of the mines are common tasks in mining operation. The estimation of the mineral resources available as well as monitoring of extracted volumes is based on extensive field sampling, geological sampling and terrain surveying.
By means of advanced Geographical Information Systems (GIS) the data are processed and detailed information about resources, reserves, grade control and production is generated. One key input variable for the GIS analysis (Block Modeling) is a Digital Terrain Model (DTM). Commonly the mine terrain is surveyed through terrestrial approaches. However, an alternative approach is the generation of a DTM by means of high resolution satellite data.
Objective of this Earth Observation project was to demonstrate the potential of very high resolution satellite data in the generation of very precise DTMs useful in the estimation of extracted material over a defined period of time. For the mine in Ouenza (Algeria), which is currently undergoing an entire review of the resources and reserves, Earth Observation-based DTMs have been derived in order to test this alternative approach.
Executive Summary (extracted from the Service Operation Report)
VIASAT GeoTechnologies produced, through a project carried out by LuxSpace for the European Space Agency,
High-resolution satellite orthoimage maps were produced to demonstrate some of the benefits of using Earth Observation data to monitor ArcelorMittal's mine site operations. Two stereoscopic pairs of IKONOS 1m color images were acquired over the Ouenza mine site in Algeria, the first one on August 27th and the second on November 1st.. The idea was to produce two separate digital elevation models (DEMs) on two different dates so that they could be processed to yield the amount of mineral that was extracted between the two dates.
Most elevation features were extracted manually by traditional (more precise) photo-interpretation techniques. The second stereo pair was fitted over the first one by performing a relative orientation with tie points. This allowed the two image pairs to stack perfectly on top of each other.
The fact that GCPs were unavailable for the study site resulted in an absolute positioning accuracy of < 15 m. With ground control points (GCPs), it would have been possible to obtain < 2 m absolute positioning accuracy with the IKONOS imagery used. However, the relative positioning accuracy is < 2 m.
The greatest challenge during the project related to the acquisition of two stereoscopic satellite image pairs one month apart, preferably at the beginning or at the end of the month. The first pair was easy to acquire within the defined time window, namely because of suitable meteorological conditions in this part of the world at the end of August. However, it was possible to acquire the second stereo pair only two months after the first acquisition, instead of one month later, because of the heavy cloud cover at the end of September/early October. This situation, however, should not be of great concern because (1) the launch of new high-resolution satellites (GeoEye-1 in September 2008 and WorldView-2 in 2009) increases the probability of acquiring stereo pairs in specific time windows and (2) stereoscopic radar imagery (in particular TerraSAR-X) can yield, regardless of cloud cover, very interesting results.
The products as specified have been quality checked by LuxSpace S.à.r.l. with regards to completeness and perceivability prior to delivery to the end-user.
ASSESSMENT OF IMPACT AND BENEFIT BY THE USER
The utility assessment has been carried out based on a report prepared by a specialised company (Maptek) working for AM on the mining management / operation and monitoring the work progress (excavations) using field surveys.
The ArcelorMittal mining expert stated that he was very positively surprised about the quality of the results of the service. He said the service provided good results, especially in terms of accuracy, and that "it is a very useful tool". Regarding the follow-up of the project, AM will investigate in-house and elaborate a cost-benefit study.