Rough Terrain
E-SCAN field instrumentation is designed for routine use
where other ground geo-electric techniques can't go.

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Left, an intrusive gold property, Sierra Nevada, south of Lake Tahoe. Using of old drill roads, a five-wheel ATV was used to distribute stockpiles of wire and electrodes at several high points across the square-mile property. Crew then installed the E-SCAN system, laying wire and installing electrodes down the steep slopes, each excursion ending with an ATV-ride back to the top for the next run. Time, cost, risk?
Above is some of the core area of a 3D E-SCAN geothermal survey on Mt. Makushin, Unalaska Island, the Aleutians, for Alaska Power Authority. Oversteepened, dissected, unstable ashfall slopes predominate, the wet grass offering no handholds to arrest a fall toward the dangerous white water that fills most gullies. The canyon in the distance (upper left) is 250 metres deep, needing helicopter wiring assistance. Time, cost, risk?
The first 3D E-SCAN survey, for the Geological Survey of Canada was on the Mt. Cayley property of BC Hydro and Power Authority. The view is looking north across Mt. Cayley. The Squamish River valley is in fog to the left. The survey's targeted area extends from behind the viewer, to include the steep airfall ash ridge that extends up to the main edifice, and everything past the right edge of the photo. Two years prior, best-efforts dipole-dipole array resistivity traverses through the area had identified a conductive anomaly system which offered 11 plausible anomaly interpretations. E-SCAN true 3D results cleared up the c onfusion, firmly rejecting 10 of the candidates. In some rough terrain, the crew, camp, groceries, equipment, wire,- everything comes in and goes out by helicopter. Time, cost, risk?

The entire 15 square mile Makushin property was wired, shot in
full 3D E-SCAN, and then cleaned up, in 24 days by a crew of six.
The project was cost-estimated from maps in San Francisco, and a
fixed price bound into the survey contract. Camp and helicopter
costs were separate, being already established to support a drill
crew. Both time and cost estimates were met, despite the remote
site, extreme terrain conditions and unpredictable, wild weather.
The client remained risk-free and fully protected, except for the
possibility of helicopter cost overruns, which did not occur.

Time: doubled
Cost: 50% premium over flat land
Risks to client: helicopter cost overrun, and extreme
weather force majeure. Neither occurred.
The Zaca property was wired, shot in full 3D E-SCAN, and
then cleaned up, in 10 days by a highly-skilled crew, on
a guaranteed-in-advance fixed budget. As predicted, this
steep square-mile took twice as long to survey as similar
size projects that have been done in open, ATV-amenable
sagebrush pediment. By contract, the client was fully
protected from any cost overrun exposure.

Time: doubled
Cost: 50% premium over flat land
Risk to client: none.
No helicopter, no camp costs (motel).
John Deere AMT-600 five-wheelers, with 2 PSI flotation tires, are more often found
traversing delicate ground. These AMT-600's can carry 600 pounds of wire,
while leaving virtually no soil indentation. The ATV fleet is rounded out with
4-wheel- and 6-wheel-drive Polaris ATV's, with high-elevation EFI fuel systems,
similar carrying capacities, and even better steep-terrain performance.
Even in this first-ever 3D E-SCAN survey, costs were estimated
in advance and the field contract completed on a guaranteed cost
basis. The GSC and BC Hydro remained risk-free and fully protected
from cost overruns. Helicopter use (client expense) was less than
planned for. Camp was provided by Premier as part of the fixed
cost contract.

Time: doubled
Cost: 50% premium over flat land
Risk to client: helicopter cost overrun (did not occur).
                For further explanation and illustrations see the "TECHNICAL BACKUP" link.

True 3D geo-electric models
      "True 3D" refers to a comprehensively hard-data-supported 3D inversion model, whose objectivity is secured provision of a genuinely 3D raw data set, one that is rigidly defined as (1) dense, (2) uniformly distributed, (3) all-directional, (4) consistently over-deep measured data, with inherent characteristics sufficient for the (5) objective recognition and correction (or elimination) of questionable data.

      Using the complete set of appropriately positioned and oriented raw data values, the True 3D process can actively define and constrain every part of the entire 3D earth model, including "uninteresting" background areas. Virtually no earth model aspect is left to the infill interpolation, extrapolation, smoothing or other programmed estimations that most inversion algorithms must employ to ensure a 3D model result through areas represented by sparse or incomplete raw data.
      It follows that, for an all-encompassing (True 3D data-based) survey, there can be no possibility of an initial conceptual error in survey parameterization (pre-survey choice of survey line orientation, depth estimate, model type estimate) because no such pre-survey guesswork is required. No pre-survey parameter selection is ever needed... 3D E-SCAN samples all parameters, every time.

      Non "True 3D", by this definition, would be those "3D-looking" earth models that:

    a) are directly 3D-inverted by a 3D algorithm using non-3D raw data, e.g. sparse, single- or non-directional in orientation, or having insufficiently deep raw data, at least one of which characteristics results from any line-type DC resistivity survey array and almost all EM methods,    or

    b) are cobbled together from 1D profiles or 2D sections, arithmetically merged or graphically stitched, based on the questionable assumption that an objective 3D model can be obtained from some number of adjacent 2D sections or 1D stacks.