DIGITAL PROSPECTING

The computer-trained geologist can quickly produce unique property maps showing exploration targets which fit a particular geological model — and, of course, quickly stake the prospective ground. As geological models change and as more geophysical and satellite remote-sensing data become available, new exploration target maps can be produced. The tools used to accomplish this are Image Analysis Systems (IAS) and Geographic Information Systems (GIS). Used together (and in that order), they have the potential to become a powerful aid in mine-finding. But those who make the software and hardware for IAS and GIS have not always thought of the systems in these terms. Linking the two has come about only after several years of growing pains. Only recently have Dipix of Ottawa (an IAS-manufacturer) and Environmental Systems Research Institute of California (a GIS-manufacturer) teamed up with Intergraph Corp. of Huntsville, Ala. (a workstation-manufacturer) to supply integrated systems. PCI Inc. of Toronto (an IAS-manufacturer) has joined forces with TYDAC Technologies of Ottawa (a GIS-manufacturer) for the same purpose. Geological mapping is just one application of this technology.

The difference between the two tools is simple. With an IAS, the geologist looks at the wealth of raw remote-sensing information bit by bit (or pixel by pixel) and interprets it individually. This interpreted information is used by the geologist on a GIS and is reinterpreted by relating the individual bits of information to the other bits around it. In essence, putting the information into context.

When GIS first came to the attention of exploration geologists in the 1970s, there was a flood of papers on possible applications. Then, as explorationists jumped on the geobotany bandwagon in the late ’70s and early ’80s, the attention of the academic community switched to IAS. Now the pendulum has swung back to GIS. But practitioners are taking a more realistic approach based on what they’ve learned over the past 10 years.

Companies and government geology departments are no longer attempting to parachute exploration geologists from the northern bush into a sophisti cated computer workstation in suburbia and expecting them to find a mine. Instead, they are taking the so-called “technology transfer” approach. The idea is, first, to get geologists used to the idea of working with digital data. It is hoped that they will then become curious about the potential for manipulating the data and incorporating it with other digital data. The first step uses portable computers and “bit pads” in the bush for storing field information. The next step will be to purchase IAS and GIS workstations and train the geologist to interpret the information.

At least three independent geological consulting companies, GEODAT Information Services of Fredericton, N.B.; Northwest Consulting Services of Bathurst, N.B.; and Gregory Geoscience of Ottawa are equipped with GIS hardware, software and expertise. GEODAT began offering a GIS service to exploration companies in November, 1988, according to President Michael Loden. Gregory Geoscience is planning to offer a similar service this year. That company is still doing in-house research.

Environmental Sciences of Sidney, B.C., markets a software package called QUICKMAP. It is a user-friendly way to incorporate point data with existing digital map files, Product Manager Peter Wainwright says. The company also markets a package called MINGRAPH PC which contains text and graphic information from the B.C. Geological Survey’s mineral occurrence data base known as MINFILE.

Most exploration companies already own computers, so the biggest hurdle will be buying the software and training people in its use. But Loden believes there is still room in the early years of the technology for a consulting service which interprets data collected by companies. His company takes seriously the confidentiality of information. Only two people are privy to the clients’ information. About two months are required to become proficient in the use of a GIS workstation. But a user has to know a variety of disciplines, Loden says. He was working on the first consulting GIS job for a junior exploration company at the time of our interview.

A few forward-looking geologists are already taking advantage of free access to a $250,000 storehouse of LANDSAT information accumulated by the Ontario Centre for Remote Sensing (OCRS), in North York, Ont., since 1973. By projecting satellite images reproduced on transparencies (costing $200 each) on to existing geological maps (using an optical projection device called PROCOM-2, marketed by Gregory Geoscience), these enterprising individuals plot unmapped linear structural features on to the maps to assist and confirm field work and geological interpretations.

Once all provincial governments digitize the 1:20,000-scale base maps in their files, companies can incorporate the digital information accumulated in the field on to smaller-scale maps. The federal government is in the process of digitizing its large-scale (1:50,000-scale), topographic maps. Satellite data (from the U.S. LANDSAT and French SPOT satellites) and high- resolution aeromagnetic data are already collected digitally, and the federal government is to launch a RADARSAT satellite in the 1990s, which will collect even more radar data worldwide. Putting all this information on to one paper map (a form of presentation with which all geologists are familiar) may become as valuable to exploration geologists and prospectors in the 1990s as the trusty hammer has been in the past. In areas which have not been mapped at the 1:20,000-scale, electronic data bases will accelerate the job of mapping in the field.

The bottleneck at the moment lies in getting the reference maps (which show the location of lakes, rivers and infrastructure) digitized. Automatic digitizing scanners are available, but the technology is still primitive, says Richard Mussakowski, staff scientist at the OCRS. Only about 2% of the reference maps covering Ontario are in digital form. By comparison, the OCRS has compiled about $1 million worth of digital LANDSAT multi- spectral scanning data (with a resolution of 80 m) covering all of Ontario, a considerable amount of LAND-SAT thematic mapping data (with a resolution of 20 m) covering about 10% of the province and very little SPOT pancromatic data (with a 10-m resolution).

The first geological compilation map produced in Ontario, a 1:25,000- scale version of the Goudreau-Lochalsh area near Wawa, Ont., was put together by the OCRS in September, 1988 (see accompanying illustration). Covering an area 10 km wide and 15 km long and centred on the Magino mine, it used radar data collected by the Canada Centre for Remote Sensing from an airborne survey conducted in 1988. The map was produced using overprinting technology on a Versatec electrostatic plotter at the OCRS. Ontario Geological Survey (OGS) geologist Norm Trowell, who was involved in the project, plans to take the map out into the field to attempt to confirm some of the features interpreted from the remote sensing data. The area was mapped about five years ago by Dr Ronald Sage.

Two side-scanning radar surveys are planned in Ontario this year and next. One will collect information in a 68-km-wide swath
south of Wawa and another will be flown along a north- south flight line perpendicular to the previous two surveys. This, it is hoped, will enhance any north-south structural features in the area.

Since the map was presented at the OGS open house earlier this year, considerable interest in the map and the technique used to produce it has been expressed by the exploration industry, Mussakowski says. Other areas of the province, including the Geraldton- Beardmore area will be mapped in a similar fashion.

Once all reference maps in each province are available in digital form, junior exploration companies should find it advantageous to purchase their own IAS/GIS software. At least one gis (marketed by Tydac Technologies of Ottawa), called SPANS, allows exploration geologists to produce new maps on relatively inexpensive micro- computers. To do this, the program draws on information from numerous other maps which are stacked in the computer’s digital memory. Up to 15 maps can be stacked in such a way. Because of the volume of data, this capability normally requires the power of a mainframe computer. But SPANS uses a technique of storing digitized data in what are called quadtree files, which save an enormous amount of memory space. The SPANS system is the only microcomputer-based system equipped with this capability, according to Adla Worobec, manager of Canadian marketing for Tydac. SPANS can also accept data in the other two file formats — vector and raster formats — commonly used in GIS systems.

Who is using the SPANS system? Research Scientists Gordon Watson, Andy Rencz and Graeme Bonham- Carter of the Geological Survey of Canada in Ottawa have used them to assess the gold potential in a 30-sq-km area in northeastern New Brunswick. Bedrock geology was digitized by raster scanning at a 1:50,000 scale to produce a simplified geological map. Point locations of 18 gold-bearing mineral occurrences from the CANMINDEX data base were superimposed on the map. Then geochemical data from 492 till samples, analysed for 17 elements, and 498 stream sediment samples, tested for 11 elements, were used by the GIS to produce interpolated thematic maps. Lineaments, airborne geophysics and remote- sensing data were also used to produce individual maps which were then combined to produce a final map showing gold potential. The U.S. Geological Survey is getting into the act, too. Last fall, it awarded an $835,000 (us) contract for software and training on up to 80 SPANS systems. The systems will be used to digitize up to 54,000 map sheets (1:24,000 scale). Environment Canada, too, has 34 SPANS systems in 15 locations across Canada.

Dr Simsek Pala, director of the OCRS, used the Tydac system to digitize information on the vast peatland resources in Ontario. Using the quadtree format, Pala managed to store all the information on two floppy discs. Using the vector format, the data would fill 1.5 gigabytes of memory (a stack of magnetic tapes). IAS/GIS are not just for big government, though. A handful of geological and engineering consulting companies (GEODAT Information Services, of Fredericton, N.B.; Gregory Geoscience of Ottawa; Northwest Consulting Services of Bathurst, N.B.; and Monenco of Calgary) have been using SPANS. Gregory Geoscience has linked its optical projector and digitizing board to a SPANS system for image analysis applications. The company is marketing this product and will soon interpret data on a SPANS GIS for junior or major exploration companies that cannot afford a GIS of their own.

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