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Optimizing Ground Coverage


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Here is a thread I started about the 800 but it includes a lot of 'ground coverage' discussion.

 

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Good link to your older thread, Mitchel. Similar to the way conditions change at a beach, conditions at the same turf site will change also. Ground moisture and grass height (gopher activity also) will affect target responses (especially the deeper targets)...So even if a th’er is practicing thorough/persistent/smart ground coverage, there will be numerous deep targets that will be passed over on certain days/weeks/months at your hunt site...In other words, Mother Nature (even the frequency/timing of the lawn being mowed ☺️) play a huge part in your ability to recover the deeper/older turf targets on any given day.....all the more reason to never give up on a site, simply because it didn’t produce very much for you after a few hunts.

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To answer your question, it all depends on were, and type of signal and it's rate.

I hunt virgin ground so rubbish signals are rare, however they indicate human activity. The speed slows down and I evaluate the site and try and hit a nugget. Some times I hit a nugget and the only initial indication was shallow looking ground. Once the gold nugget is caught, I have to call the wife over and keep my distance looking for the extent of the patch. Then I grid and grid the whole area with shorter straight strokes and moving the coil 75% forward at each end of the swing. I have been told that my slow swing is a bit fast but it works for me. A method of gridding is with the lightest chain I can to leave as little evidence as I can that it has been chained. I always keep the grid line on my right and go clockwise around any tree or obstacle to get the coil as close as possible. This works for right handed detecting. Some of my patches have exceeded 1 mile by  ½ mile and has taken many weeks to cover all of it. I must point out that I have many day find no gold in new location even those the general area is geological correct and not random selected non gold indication ground.

 

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4 hours ago, geof_junk said:

A method of gridding is with the lightest chain I can to leave as little evidence as I can that it has been chained.

That's to reduce the chances that other detectorists know you are searching the area?

 

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3 hours ago, GotAU? said:

...do random transect line sampling first in order to see if there are any targets or patches in the area and then [grid]ding off areas where presence was determined in order to clean up afterwards.

Great definition of patch hunting. 👍

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GotAU:  You have introduced an interesting approach to metal detecting and I would like to explore this technique in further detail as applied to nugget hunting.  I have some specific questions on application and would like to use a hypothetical case as an example (I apologize in advance for the detail).  For this example I have chosen a grid approach and not the random transect.  So let’s assume: 1) an arid or semiarid environment such as Nevada or Arizona; 2) the general area has a history of gold production; 3) placer mining information is sketchy but there may be a potential for placer nuggets although they may be small in size (well under an ounce); 4) we have located the area on Google Maps; 5) historical data shows patented mining claims that we have eliminated from our area of interest; 6) BLM records show some active claims that we have eliminated from our area of interest; 7) the general topography is of low to moderate relief; 10) the area is traversed by a dendritic drainage pattern with many 1st and 2nd order ephemeral tributaries; 9) we have a topographic map of the area; 10) neither Google Map nor the topo map show any sign of workings; 11) only one unidentifiable outcrop is visible on Google Map; 12) we have identified a small drainage of interest that cuts across a two-track “road”; 13) our area of interest is a one-quarter mile square; 14) we grid the area into 10-ft. by 10-ft square grids (this produces about 17,424 squares; 15) the grid is plotted on the topo map; 16) we number each grid square with a unique number starting from the upper right corner using the same scheme as the public land survey grid; 17) we use a random number generator or table to choose 10-percent of the grid squares; 18) in the field we test each chosen grid square.

For the field procedure: 1) we start at the bottom left corner of the of the grid square and proceed slowly toward the opposite end; 2) a 4-ft wide left-to-right coil sweep is used with 10% to 20% coil sweep overlap; 3) this is repeated three times to cover the area allowing for a side-to-side overlap of about 10% to 20%.; 4) this approach is then repeated at 90 degrees to the first direction; 5) a large coil is used initially to search for large nuggets; 6) a smaller coil is then used to look for smaller gold.

My questions:  1) is the area chosen too large; 2) is the size of the individual grid squares appropriate (too large or too small?); 3) is a randomly selected 10% subset the proper size (you mentioned 30%); 4) is the two-coil approach appropriate; 5) should I have applied the random transect first and used this detailed approach on any areas with positive results; 6) what other modifications should be made to this technique and what other details have I missed?   If I have completely missed the point please feel free to say so.

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3 hours ago, Cascade Steven said:

GotAU:  You have introduced an interesting approach to metal detecting and I would like to explore this technique in further detail as applied to nugget hunting.  I have some specific questions on application and would like to use a hypothetical case as an example (I apologize in advance for the detail).  For this example I have chosen a grid approach and not the random transect.  So let’s assume: 1) an arid or semiarid environment such as Nevada or Arizona; 2) the general area has a history of gold production; 3) placer mining information is sketchy but there may be a potential for placer nuggets although they may be small in size (well under an ounce); 4) we have located the area on Google Maps; 5) historical data shows patented mining claims that we have eliminated from our area of interest; 6) BLM records show some active claims that we have eliminated from our area of interest; 7) the general topography is of low to moderate relief; 10) the area is traversed by a dendritic drainage pattern with many 1st and 2nd order ephemeral tributaries; 9) we have a topographic map of the area; 10) neither Google Map nor the topo map show any sign of workings; 11) only one unidentifiable outcrop is visible on Google Map; 12) we have identified a small drainage of interest that cuts across a two-track “road”; 13) our area of interest is a one-quarter mile square; 14) we grid the area into 10-ft. by 10-ft square grids (this produces about 17,424 squares; 15) the grid is plotted on the topo map; 16) we number each grid square with a unique number starting from the upper right corner using the same scheme as the public land survey grid; 17) we use a random number generator or table to choose 10-percent of the grid squares; 18) in the field we test each chosen grid square.

For the field procedure: 1) we start at the bottom left corner of the of the grid square and proceed slowly toward the opposite end; 2) a 4-ft wide left-to-right coil sweep is used with 10% to 20% coil sweep overlap; 3) this is repeated three times to cover the area allowing for a side-to-side overlap of about 10% to 20%.; 4) this approach is then repeated at 90 degrees to the first direction; 5) a large coil is used initially to search for large nuggets; 6) a smaller coil is then used to look for smaller gold.

My questions:  1) is the area chosen too large; 2) is the size of the individual grid squares appropriate (too large or too small?); 3) is a randomly selected 10% subset the proper size (you mentioned 30%); 4) is the two-coil approach appropriate; 5) should I have applied the random transect first and used this detailed approach on any areas with positive results; 6) what other modifications should be made to this technique and what other details have I missed?   If I have completely missed the point please feel free to say so.

You are setting up an interesting scenario for sampling here! So first off, I would think that it would be best to start by using a set of transects located randomly across the most likely areas to have any gold, and perhaps sample along the transects using randomly placed quadrats or grids along those transects.  How large to make the grids and how many to use would be mainly determined by the amount of effort you are willing to do, but also based on the size of the sampling area and length of the transects.  Keep on mind that the transects are very long grids themselves, perhaps only 2m wide but hundreds of meters long.  There are several biostatistic formulas for determining the best size for quadrats to effectively sample an area, and it can get quite complex.  Here’s a reference about it  which may give some ideas.

I will continue with the rest of my input here tomorrow, kinda late so I will just leave a good reference about it for now. But see what the author says about how long quadrats catch more patches for sampling, it’s an interesting discussion about quadrat shape  in the text.  One thing for sure about all this, it’s easy to overthink it! definitely rely on local conditions and your knowledge of where gold typically is to help in the search, but some knowledge and understanding about sampling with transects and grids may help as well!

https://www.zoology.ubc.ca/~krebs/downloads/krebs_chapter_04_2017.pdf

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Quote:--- One thing for sure about all this, it’s easy to overthink it! definitely rely on local conditions and your knowledge of where gold typically is to help in the search, but some knowledge and understanding about sampling with transects and grids may help as well!

That will reduce the time to pick up a target, if there is any in you selected area and remember that shallow ground are the best and easiest to find a nugget your target area, but some times gold is not where you think it is and the straight line random lines will pick up an unexpected target. Remember you are only looking for the first nugget at the start of patch finding search.

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23 hours ago, GotAU? said:

I... did a lot of small mammal studies where we had to sample wide areas for determining population size and density using  various statistical sampling methods.

Determining the best sampling protocol in a new area for gold or for targets on a beach may not be much different than what we did for determining how to set up our trapping areas to maximize our efforts.

I wasn't anticipating details to this level of scientific relevance, but that's one of the advantages to asking a question as contrasted with stating an observation/opinion to start a thread.  Being a scientiest (more than just 'at heart') I'm pleased and intrigued by the direction this thread has gone.  I think @jasongis one who will be particularly interested in this as he takes a scientific approach to prospecting and gold recovery.

Thanks to all who have responded so far and will continue to respond.  I may chime in at some point with my thoughts and motivation (specifically the ones that haven't been addressed yet, at least in the detail I was hoping for) but for now I'll sit back and enjoy the scenery.

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