Many prospectors randomly scan an area until a nugget is found. However, this unorganized method resuls in a large proportion of ground being uncovered, potentially leaving behind valuable gold. The best way to guarantee that an area is thoroughly scanned with a gold detector is by planning ahead and creating a grid. A grid is defined as a pattern of straight lines that cross over each other in space, forming squares, and is used to help recognising your position in the field. There are two ways to define a grid on the ground: the Traditional Gridding Method using pegs and a compass, and the Modern Gridding Method using a GPS.
Traditional Gridding Method
The Traditional Gridding Method involves using wooden pegs to mark out an area. The pegs are laid out so that the ground is subdivided into small, manageable square blocks of land. This helps with locating yourself in the ground and making sure the area is covered thoroughly.
The main tools required for a traditional gridding method are a paper map, wooden pegs, a hammer to put the pegs on the ground, and a compass.
Make sure the pegs are at least 1.5m tall. This method works best when the ground is flat-lying, so you can see the pegs around. This helps you visualise your spatial location within the grid.
The first thing to do is define a point of origin from which all other point locations will be established. It is important that this peg is easily located in the field, so it should be close to a recognizable landmark. The location of the peg must be marked in your paper map.
Ideally this origin peg should be painted with a different colour to help differentiate it from the others, and would be labelled as “Origin”.
Then using the compass, a set direction is followed, for example, North. Then walk for example 100m in that direction and put the peg in the ground. The peg should have a label on it, in this case for example I would be naming it “100m North”. This should also be marked in your paper map.
An easy way to make sure you walk in straight line is by fixing your sight on a landmark such as a tree or large tussock of grass. Another trick is marking the pegs with a colourful tape so it can be seen from the distance.
Measuring the exact distance from the origin point to the next point can be challenging. It takes a bit of practice to get the distance right, but the easiest way to make sure all pegs are spaced at the same distance is by simply counting your steps between points.
In areas of open bushland with flat ground such as in the Goldfields of Western Australia, a laser measuring tool can be used to accurately define the distance between pegs.
The next step is to walk another 100m West and put another peg. This peg would be named “100m North, 100m West”. Then walk another 100m South and label this peg as “100m West”. This would create a square of 100x100m with labels easily recognizable.
This grid is then known as a 4×4 grid. Larger grids can be created using more pegs and marking out at set distances from the Origin, e.g. 200m, 300m, etc. These grids will then be 8×8, 12×12, 16×16, etc. Obviously the larger the grids the more time will be required to mark these out, and more pegs will be required.
An alternatively technique which is valid in open bushland is creating the divisions by driving a vehicle in a straight line, ideally using a compass to make sure it drives in a set direction, e.g. North.
Then the process is repeated until the area is covered by parallel wheel tracks. It is best to use wooden pegs at the beginning and end of each track so they can be seen from the distance and between tall grass.
Then, the area between pegs is covered with the gold detector. Depending on how big a prospective area is, you might want to use bigger grids, e.g. 8×8, 16×16, etc.
Modern Gridding Method using a GPS
This is by far my favourite method, as it makes use of modern technology and eliminates many of the obstacles described earlier. It is accurate, reliable, and faster. It does not require any marking on the ground, and although it can be setup in the field, it is ideally carefully designed at home before the commencement of a gold detecting trip.
The most important thing before commencing any gridding is making sure you are familiar with the use of a handheld GPS. These are very useful for gold prospectors and will make your life easier.
There are many ways to set up a grid, however my favourite is defining a number of parallel lines set-up perpendicular to the lithological trend. E.g., if the rocks are oriented in a North-South direction, the grid is planned East-West.
The lines in the GPS are then walked while detecting. Obviously, the closer spaced the grid is, the better the chances of finding more and better gold, but the more time consuming it is. Finding the right balance between gridding space and time depends on personal preferences.
For amateurs, a grid spaced about 25m might be enough, but for the professional prospectors, you want the grid lines to be just as wide as the width of your sweep, typically about 1.5m.
Using a GPS for gridding not only guarantees that all ground is covered, it also gives you that sense of security when walking away from your vehicle, as it makes it easier to find your way back when you get distracted (or excited, when finding gold).
Conclusion
Although there are two ways to do the same gridding job, it is obvious that taking the time to learn how to use a handheld GPS pays off because ultimately it makes the job much easier.
The traditional gridding technique might work well in flat arid areas such as the Goldfields of Western Australia. However, the method can be difficult and unreliable in more challenging terrains such as the Georgetown Goldfields in Queensland.
Some prospectors in the past have even relied on dragging heavy chains attached to their belts to ensure the ground is marked so they don’t loose time scanning it twice. However, in the 21st Century it is best to make the most of what modern technology has to offer.
In recent times, the use of drones has had a massive impact in modern gold prospecting. Being able to visualise the location of dumps and old mine workings is a great way to preview in the field the direction of hard rock mineralisation. Ideally, grids should be perpendicular to the direction of veins and rock fractures. Advanced gridding and exploration techniques will be covered in another post, stay tuned.