structured beach survey idea

[udon1nano]

I'm just running this out for the community to shoot holes through my reasoning. I have a large, open beach are on a barrier island in a marine bay that I would like to begin detecting for coins and other metallic relics. The area is pretty large - probably 2 - 3 square miles. I've done some infrequent, small-scale detecting (with a very limited amount of finding so I am largely a neophyte (albeit one with ambitious ideas). I suspect that when I try to survey an area such as this by sweeping my handheld detector, I'm probably missing quite a sizable fraction of the beach as I walk, no matter how careful I am. I'm convinced that if I try to cover consecutive "swaths" by walking long paths back and forth and trying to join the edges of those paths by eye, I'm either missing or duplicating a significant amount of coverage, probably both. This quest is largely recreational, but otoh it would nice to find "stuff" and I'm a bit anal on the subject of efficiency.

For quite a while I've been toying with the idea of somehow structuring the scans so (nearly) no ground is missed or duplicated, and doing this in such a way that the "hits" are recorded somehow, with actually pinpointing and digging left for a dedicated task after the survey scan for an area is completed. My thoughts are to make a wheeled chassis of PVC pipe or something similar to mount the detector head, and also mount a GPS display on the handle. There would be linkage between wheels and detector head mount that would move the head form side-to-side as the chassis is pushed over the sand. I would stake the area to by surveyed and use florescent line to temporarily delineate parallel scan paths. Each time I got a promising ping from the detector I would record the lat/long coordinates and optionally mark the spot with a highly viable stake or flag. After completing the survey for an area, I would come back to the "hit" locations and use the pinpointer to help me isolate and dig any items that are actually there.

I realize that the marking for initial survey and a chassis for the detector head can be considered as separate items (in other words, potentially I could do the stake out, scan, and pinpointing steps as described with a handheld detector), so feel free to treat them as such if you wish. If anyone sees problems with the basic concept(s), please reply with objections (especially if you have tried something similar to this and failed).

Here are some of the questions I would like opinions about. How much advantage is there in detection accuracy to maintaining an exact distance from detector head to sand, and an exactly parallel side-to-side swing of the head, as compared to the less even motion that is typical of hand-held scanning? How much side-to-side excursion of the head is required for optimal discrimination of buried items (I realize that probably varies depending on the detector, but some generalized observations would be helpful). Is there an optimum relationship (or effective limits) on the forward vs horizontal speeds of the head? I'm sure I have a lot more to ask the experts here on this idea, but I'll stop there for some brevity in this post (and in case someone points out an obvious and convincing reason why this can't work at all that I have stupidly missed Thanks for your help!

 

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[Treasure_Hunter]

What kind of detector are you using and what kind of coil, is the coil a Concentric or Double D, it makes a big difference.

 

[Mackaydon]

Without a specific target search, I wouldn't worry about gaps in my swaths over a 2-3 square mile area; just enjoy the outdoor experience and hunt where people have been.
Don.....

 

[Terry Soloman]

You are overthinking this. Start at the high tide line and detect down to the water, or into it. Turn around and detect back up to the high tide line. It should take you about an hour to grid a 35-40 meter stretch of beach front. You'll be able to identify the "coin line" in this way, and where the heavy targets are along the beach that particular day. Tides, winds, and currents change beaches overnight, especially in storm conditions. Stuff dropped in the summer, is pushed UP on the beach in the fall and winter.

 

[udon1nano]

If my objective was collecting coins dropped or washed up recently, this would be overkill. This is a site that at one time (1870s) was reported in several sources to be the location of multiple shipwrecks containing hard currency or bullion. Yes, I'm sure such statements were nearly all unsubstantiated rumour even then. However, I do know that it is and historically has been a prime site for a boat or ship to get washed ashore in a storm. There has been no mention of this site in the shipwreck context in many decades, according to my research. Very high probability of that meaning that the rumours were false all along. The other, much more remote possibility is that it was completely forgotten, for some other reason. I can tell you from frequent direct observation that there has almost certainly been no recent metal detecting activity there (for at least the past 12 years). In fact, there has been nearly zero foot traffic of any kind. Other nearly beaches are much more accessible for recreational (seasonal) use. Occasionally a boat will anchor nearby for fishing, or a clammer will rake in the bar at water's edge, but that is about it. I do regard this as a recreational activity, because I really like the damned place (I'm a loner at heart and if I find nothing, as is almost certain, that's perfectly OK. OTOH I'd hate to miss something that is there, and if there really is anything, it will have been there for a long time. None of that may change your recommendation, but I did want to correct your assumption about the type of target.

 

[cudamark]

On your question of overlap or not.....on a beach with few signals, I would not overlap or worry about gaps. Use the largest coil you get for your particular detector and cover as much ground as possible. It's usually a numbers game on a large area like that, so, careful gridding is not necessary (unless you find a hot spot, then grid away!) I'd rather have "virgin" ground under my coil at all times and cover more ground, than overlap and cover the same ground more than once, unless I'm looking for something specific that I know is there and are trying to find, or, as I mentioned, I start finding lots of good targets in a relatively small area. Coil control (as in keeping an even distance from coil to ground) can help under some circumstances.....mainly at higher sensitivity and in mineralized ground. Choice of detector in a given area is important in this regard. Some machines are better at handling adverse conditions than others.

 

[cudamark]

If you know the area in question, keep an eye out for changes in sand level. If sand washes away, that's the time to do some serious hunting. Heavy metals such as gold, platinum, lead, and to a lesser extent silver, don't usually "wash up on the beach" unless there is a hurricane or similar. Most of the time, it's the sand washes away and exposes the heavier metals.

 

[udon1nano]

What kind of detector are you using and what kind of coil, is the coil a Concentric or Double D, it makes a big difference.

I have two: an older Fisher 1280x with an 8" mono concentric coil; a fairly recent Garrett Sea Hunter Mark II with both the standard 8" coil and optional 10x14" coil. I think both of the Sea Hunter coils are also concentric, but I couldn't find that attribute listed directly in the specs.

 

[udon1nano]

On your question of overlap or not.....on a beach with few signals, I would not overlap or worry about gaps. Use the largest coil you get for your particular detector and cover as much ground as possible. It's usually a numbers game on a large area like that, so, careful gridding is not necessary (unless you find a hot spot, then grid away!) I'd rather have "virgin" ground under my coil at all times and cover more ground, than overlap and cover the same ground more than once, unless I'm looking for something specific that I know is there and are trying to find, or, as I mentioned, I start finding lots of good targets in a relatively small area. Coil control (as in keeping an even distance from coil to ground) can help under some circumstances.....mainly at higher sensitivity and in mineralized ground. Choice of detector in a given area is important in this regard. Some machines are better at handling adverse conditions than others.

Good advice, thanks! I have two detectors, an older Fisher 1280x with 8" mono coil, and a Garrett Sea Hunter II with both standard 8" and optional 10x14" coils. I take it you would opt for the Garrett with the larger coil in this circumstance? This is "sugar" type beach sand bordering a marine estuary, so I wouldn't think mineralization would be likely be a big issue.

 

[Sandancer]

Way too complicated in my opinion. Drag your scoop behind you to form a line you can follow, move over the width of your swing, turn around and do the same thing in the other direction. Bring something to drink and a delicious sub sandwich, and have fun. Oh yea, use at least a 12" coil and keep your swing flat. You can do it!

 

[cudamark]

Good advice, thanks! I have two detectors, an older Fisher 1280x with 8" mono coil, and a Garrett Sea Hunter II with both standard 8" and optional 10x14" coils. I take it you would opt for the Garrett with the larger coil in this circumstance? This is "sugar" type beach sand bordering a marine estuary, so I wouldn't think mineralization would be likely be a big issue.

Given those two choices, yes, I'd use the Sea Hunter if the iron trash is not too heavy.

 

[WaterScoop]

Cheers and welcome to our forum.
Do you have any photos of your beach?
What's the lowest tide you’ve had this year?
Are you NE or SE ?
are you in the Hurricane Alley ?

Are you detecting the beach on the ocean side of the barrier island or the one facing the land?

I like to do a ton of research that’s my strong point. Regarding the machines and coils to use Needed I do t hold a candle to the knowledge of the fellas that posted above.

Cheers

 

[Treasure_Hunter]

I have two: an older Fisher 1280x with an 8" mono concentric coil; a fairly recent Garrett Sea Hunter Mark II with both the standard 8" coil and optional 10x14" coil. I think both of the Sea Hunter coils are also concentric, but I couldn't find that attribute listed directly in the specs.

Concentric coils narrow as the signal goes down so using a 8" concentric coil will only give you a couple inches search pattern at full depth. You need to be using a large DD coil to get max coverage in your search. A 15" DD coil would work much better for your searching.

 

[udon1nano]

Well, both but primarily the inlet side. There are a couple of spots "inland" that look interesting, but are (probably) small enough to investigate without use of a detector. Away from the water, there is also a lot of area overgrown with reeds, vines, and other scrub that seems like it would be difficult to sweep with a detector in Winter after vegetation has died off, and would be literally impossible during growing season (couldn't even walk it then).