Questions and answers about treasure hunting and geophysics

[99thpercentile]

I haven’t seen many good posts here for a while so I want to propose something.

Ask specific questions here about how geophysics relates to treasure hunting.

For example, I had a recent question about what type of sensor may have produced a picture that was shared with me. The person said the picture was of a plastic 55 gallon drum. I did my best to explain what type of instrument most likely produced that image, why I thought that, and what the rustles would have looked like from other types of sensors.

I was asked once by the drug enforcement agency (DEA) to help locate plastic 55 gallon drums buried by drug dealers on beaches in the Caribbean that may have been full of cash and jewels.

 

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[ConceptualizedNetherlandr]

My first question is: were they full of cash and jewels?

 

[ConceptualizedNetherlandr]

My second question is: I still use my old 1980's copy of geophysics by Telford. Has that been found to stand the test of time or were there errors or shortcomings?

 

[99thpercentile]

The bad news about the DEA request was that they decided not to do it after we explained how long it would take to do the surveys. They thought I could walk up and back twice along a beach and then be done. We had to explain that our like spacing would need to be less than the smallest dimension of the target.

I think that last edition of Telford was published around 1993, it is a fine book for the technical underpinnings of most geophysical methods. It doesn't really address modern ground penetrating radar (GPR) instrumentation or processing, it doesn't address mobile time domain electromagnetic induction (TDEM), or any other method where there have been big improvements in collection speed and resolution. The biggest improvements in geophysical equipment are collection speed and resolution, the processing for some methods has significantly improved while others haven't changed much in 20+ years. A lot of near surface geophysics is bump detection and unfortunately there aren't too many ways to speed up that processing.

I typically recommend "An Introduction to Applied and Environmental Geophysics" by John M. Reynolds 2nd edition (2011) although I think he is writing a 3rd edition now. I also recommend "Field Geophysics 4th Edition" by John Milsom and Asger Eriksen (2011) for anyone interested in near surface geophysics.

 

[ConceptualizedNetherlandr]

Thank you. Very informative!

 

[Icewing]

I have been hunting a pre civil war military fort, and some other places with civil war activity.
I have always been interested in either a drone with Lidar or some type of GPR that doesn't cost as much as a car. My problem is I don't know where to start. Are you familiar with Lidar and would it even be useful on old forts and camps? Is there anything on the market for hobbyists that's worth buying?

 

[99thpercentile]

I am very familiar with LiDAR and have been using it for 15+ years. When I worked for the US Army I primarily used Trimble or Riegl terrestrial LiDAR systems. I currently own several LiDAR system from Geosun that mount on my drone.

What do you hope to accomplish with a drone or LiDAR? I use an inexpensive drone to collect imagery for photogrammetry on every site I work. I usually use my DJI Mavic 3E with an EMLID Reach RS2+ GNSS base for RTK positioning. This is a pretty cheap system that is only about $8K to generate really nice orthomosaic and digital elevation model. For bigger sites or sites with vegetation I break out either my DJI Matrice 300 or Inspired Flight IF1200A UAS units. I can connect a range of sensors to either one, camera, LiDAR, infrared, multispectral camera, magnetometers, echo sounders, etc...

Either photogrammetry or LiDAR are just providing surface level information, they don't penetrate into the ground. You can sometimes see patterns in the surface information that are indicative of what is going on under the ground.

 

[cyzak]

Hello Sir 99th can you please post a photo of the datalogger layout of the ground, that your magdrone produces please.

 

[99thpercentile]

Hello Sir 99th can you please post a photo of the datalogger layout of the ground, that your magdrone produces please.

I'm not sure what you are asking. Are you asking to see a sample dataset of mag data collected by a drone?

 

[cyzak]

Yes please.

 

[Icewing]

I am very familiar with LiDAR and have been using it for 15+ years. When I worked for the US Army I primarily used Trimble or Riegl terrestrial LiDAR systems. I currently own several LiDAR system from Geosun that mount on my drone.

What do you hope to accomplish with a drone or LiDAR? I use an inexpensive drone to collect imagery for photogrammetry on every site I work. I usually use my DJI Mavic 3E with an EMLID Reach RS2+ GNSS base for RTK positioning. This is a pretty cheap system that is only about $8K to generate really nice orthomosaic and digital elevation model. For bigger sites or sites with vegetation I break out either my DJI Matrice 300 or Inspired Flight IF1200A UAS units. I can connect a range of sensors to either one, camera, LiDAR, infrared, multispectral camera, magnetometers, echo sounders, etc...

Either photogrammetry or LiDAR are just providing surface level information, they don't penetrate into the ground. You can sometimes see patterns in the surface information that are indicative of what is going on under the ground.

Primary what I hunt and hunt for is pre-civil war forts, civil war camps ghost towns or any other early sites that might be good for metal detecting. I've seen lidar used for archeology in several documentaries and always wanted to see if it would identify places where structures once stood.

 

[99thpercentile]

LiDAR can definitely be used to identify the location of old structures or foundations, it is most useful in vegetated areas. Unfortunately, to take advantage of LiDAR you will need a way to deploy it, the sensor, and the software for processing and interpreting. To be able to penetrate vegetation you need a LiDAR with multiple returns per Laser pulse. You also need a sensor with a high point density on the ground. What this means is that for unmanned aerial system (UAS) LiDAR you will need a ~$20K+ UAS, a $30k+ LiDAR sensor, and software that can cost $10K up front and $5K per year. There are slightly less expensive combinations of hardware and software, but they typically don't have the number of returns, point density, and resolution necessary to find indicators of structures on the ground although the cheaper ones can identify a structure in the woods/forest/jungle.

Chris Fisher, and archaeologist at Colorado State University, has been pushing collecting high resolution LiDAR all over the planet to identify structures that we don't know exist due to vegetation.

Colorado State University
Chris Fisher, archaeologist who I spoke with at Geoweek
https://www.libarts.colostate.edu/people/ctfisher/
http://www.chrisfisher.science/

Denver TED Talk
Earth Archive project to LiDAR the planet

Colorado State University is fast-forwarding archaeology with tech to help future researchers understand today’s Earth
https://coloradosun.com/2019/09/04/csu-chris-fisher-wants-to-lidar-scan-the-earth/

 

[JKicker]

LiDAR can definitely be used to identify the location of old structures or foundations, it is most useful in vegetated areas. Unfortunately, to take advantage of LiDAR you will need a way to deploy it, the sensor, and the software for processing and interpreting. To be able to penetrate vegetation you need a LiDAR with multiple returns per Laser pulse. You also need a sensor with a high point density on the ground. What this means is that for unmanned aerial system (UAS) LiDAR you will need a ~$20K+ UAS, a $30k+ LiDAR sensor, and software that can cost $10K up front and $5K per year. There are slightly less expensive combinations of hardware and software, but they typically don't have the number of returns, point density, and resolution necessary to find indicators of structures on the ground although the cheaper ones can identify a structure in the woods/forest/jungle.

Chris Fisher, and archaeologist at Colorado State University, has been pushing collecting high resolution LiDAR all over the planet to identify structures that we don't know exist due to vegetation.

Colorado State University
Chris Fisher, archaeologist who I spoke with at Geoweek
https://www.libarts.colostate.edu/people/ctfisher/
http://www.chrisfisher.science/

Denver TED Talk
Earth Archive project to LiDAR the planet

Colorado State University is fast-forwarding archaeology with tech to help future researchers understand today’s Earth
https://coloradosun.com/2019/09/04/csu-chris-fisher-wants-to-lidar-scan-the-earth/

So a drone with lidar instruments are priced beyond reach for the typical hobbyist. What companies offer lidar scanning and could an average detectorist or small group afford their services?

 

[robertk]

If you're in the US, there is USGS LIDAR available on their website. There's a forum thread about it here (and probably others). You can also get apps for your phone with LIDAR maps.

 

[99thpercentile]

So a drone with lidar instruments are priced beyond reach for the typical hobbyist. What companies offer lidar scanning and could an average detectorist or small group afford their services?

I assume that there is a daily rate for collection and processing and I would assume that it is $5-$10K per day.

 

[99thpercentile]

If you're in the US, there is USGS LIDAR available on their website. There's a forum thread about it here (and probably others). You can also get apps for your phone with LIDAR maps.

Yes there is LiDAR available for most of the USA as part of the 3DEP program. Unfortunately, while this data is a great resource it is typically 1 m vertical resolution that is really useful for mapping topography but not very useful for finding buildings and foundations. Occasionally you may find something of interest to you in the free data.

3D Elevation Program​

3D Elevation Program | U.S. Geological Survey

www.usgs.gov

 

[Quinc]

Very interesting thread. Can you give us some examples of things you have found and how you found them using Geophysics? If you can post any pictures from your drone with and without lidar etc that would be interesting to see as well. =)