What mapping and surveying accuracy do I need for my mining exploration project?

By Gerry Mitchell, P.Geo, President PhotoSat

GPS survey of a PhotoSat survey ground control point.

Accurate topographic mapping and surveying of a mining exploration project requires a significant investment of time and resources.

 

For early stage mining exploration project work, 3m survey accuracy is sufficient.

Early stage mining exploration project work:

  • Geological mapping and outcrop sampling
  • Geochemical surveys
  • Geophysical surveys: magnetics, electromagnetics, induced polarization, gravity

Most early stage mining exploration projects require mapping quality topography, accurate to about 3m horizontally and 3m in elevation. This is similar to the accuracy of the hand held GPS units used by most exploration geologists to record geological observations and sample locations.

 

For exploration drilling up to the “discovery” drill hole, 3m survey accuracy is sufficient.

The initial exploration drilling will be focused on geological, geochemical or geophysical targets. Location of drill collars to 3m in XYZ is usually sufficient accuracy for the initial exploration drilling.  Once there is a discovery drill hole, project focus shifts to the confirmation and delineation of inferred resources.

 

When drilling to delineate resources after a discovery drill hole, you need better than 50cm survey accuracy.

Once the focus of the drilling campaign shifts to confirmation and delineation of inferred resources, survey quality topographic accuracy is required for the project. This is accuracy of better than 50cm in XYZ for drill hole collar locations and the locations of surface samples and trenches.
 

First, establish a survey benchmark with GPS.

The first and most important step in accurately surveying an exploration project is establishing a survey benchmark that is accurate to better than 10cm in easting, northing and elevation. The most reliable way of establishing an accurate survey benchmark is to record 12 hours of GPS signals with a dual frequency geodetic quality GPS receiver. PhotoSat provides guidelines for establishing survey benchmarks.

Mining project survey benchmark with the coordinates, horizontal projection, horizontal datum and vertical reference listed on the plaque.

 

GPS survey the drill hole collars, trenches and ground control targets.

The drill holes, trenches and at least three ground control targets should be surveyed with differential GPS.  For differential GPS surveys, the GPS signals at the benchmark, and the survey point must be recorded at the same time.  Many of the survey points can be surveyed while the benchmark survey is being recorded for 12 hours. The GPS signals at each of these survey locations should be recorded for at least 30 minutes plus one minute for each kilometer of distance between the survey benchmark and the survey location.
 

LiDAR, PhotoSat or Drone topographic survey of the project area

Depending on the size of the area, vegetation cover and location survey the project area to an accuracy of better than 50cm in elevation with airborne LiDAR PhotoSat or a Drone survey. The advantages of the different survey methods are discussed in a PhotoSat surveying white paper Comparison of PhotoSat, LiDAR, GPS and Drone surveying.

This survey will provide the topographic surface needed by the mining engineers preparing the reserve and resource volume calculations for your Preliminary Economic Assessment (PEA).

1m elevation contours and the locations of drill holes on the Almaden Ixtaca mining exploration project.

3D satellite image of the Almaden Minerals Ixtaca project showing drill hole locations and the discovery drill hole.

 

For more information, see the following:

Satellite Surveying

Mining Exploration

How accurate is PhotoSat surveying?

Accuracy Studies

mine tailings beach profile

Measure your mine tailings beach lift thicknesses, slopes and profiles from space

By Gerry Mitchell, P.Geo, President PhotoSat

mine tailings beach profile

Satellite photo of a mine tailings beach

Mine tailing beach designs have optimum slopes.

Every mine site tailings storage facility (TSF) design includes optimum slopes for the tailings beaches. Tailings beaches that are either steeper or flatter than the designed slopes can have serious short-term and long-term consequences for the capacity and cost of the TSF.  Tailings engineers control the beach slopes by modifying the composition of solids and fluids discharged into the TSF in each lift.

Detailed information on tailings beach slope design and the consequences of different beach slopes can be found on the Tailings.info website.

Elevation image of a mine tailings beach with 50cm elevation contours on the tailings beach surface.

Elevation image of a mine tailings beach with 50cm elevation contours on the tailings beach surface.

Semi consolidated tailings beaches cannot be accessed by conventional surveying.

Measuring and monitoring the tailings beach slopes are challenging.  Since the tailings beaches are semi consolidated, they cannot be safely accessed by conventional surveying methods. 

 

 

Suncor review of tailings storage facility surveying methods found PhotoSat most cost effective.

In 2014 Paul Lomond, lead surveyor for the Suncor Steepbank and Millennium oil sands mines, published a review of a pilot project assessing various methods of surveying tailings storage areas.  This review is available on the Suncor tailings surveying page.  Suncor concluded that PhotoSat surveying is the most cost effective method for surveying their tailings beaches.

 

Incremental tailings thickness (isopach) surveys

In order to control the tailings beach slopes, mine site tailings engineers need to be able to determine the actual distribution of tailings on the tailings beaches.  Images showing the increase in elevation of the beach surface between two dates show the tailings engineers the actual distribution of the tailings over the time period. 

Increase in mine tailings beach height over a three month period.  25cm contours of tailings thickness.

Increase in mine tailings beach height over a three month period. 25cm contours of tailings thickness.

Mine tailings beach profiles from PhotoSat surveys

Mine tailings beach profiles from PhotoSat surveys

If you would like more information on PhotoSat surveying, you can visit the following links:

Mining

Mine site volume reconciliations

Mine Leach Pad & Ore Stockpile Volumes

Mine Tailings Surveying

Mine Site Toes & Crests