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Ronald S. Bell, Senior Geophysicist at International Geophysical Services LLC discusses:

  • His experience with UAVs in the mineral exploration industry
  • The benefits of UAV surveys
  • The limitations and restrictions of conducting drone surveys
  • UAV sensors for mapping geology
  • The MagArrow and what the device does
  • The Crestone Crater case study
    This presentation was recorded at PDAC 2020.



Ronald S. Bell
Senior Geophysicist – International Geophysical Services LLC


32 min

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Video Transcript

[00:00:00.000](light music)

[00:00:11.130]<v ->Thank you for coming to my presentation.</v>

[00:00:15.180]Some of you I’ve met yesterday when

[00:00:17.020]I was out walking the booths and invited you here.

[00:00:20.480]I’m happy you showed up for this.

[00:00:23.010]The title of my presentation is

[00:00:24.880]UAV MagArrow surveys for improved,

[00:00:29.580]I think it’s to improve geologic mapping.

[00:00:32.960]Just before I begin, this is a MagArrow

[00:00:36.140]and Geometrics, Naiema over here is a representative

[00:00:40.098]for Geometrics, and she can tell you a lot

[00:00:42.630]about the product, that magnetometer.

[00:00:46.840]I want to start that

[00:00:48.750]so that I don’t forget to bring her into the conversation.

[00:00:52.650]Today’s talking points.

[00:00:54.310]I’m going to talk about my experience with UAVs.

[00:00:58.600]What’s relevant to, at least somewhat to,

[00:01:01.580]the mineral exploration game.

[00:01:03.760]The benefits of the UAV surveys.

[00:01:07.048]I’m going to talk about the limitations and restrictions

[00:01:10.900]of doing drone magnetics,

[00:01:13.390]actually just drone surveys in general.

[00:01:15.830]I’m going to speak a little bit about UAV sensors

[00:01:19.310]and for mapping geology and then I’m going to get into

[00:01:22.570]talking a little bit about the MagArrow.

[00:01:24.180]Explain what this device particularly does

[00:01:26.550]and then I’m going to go through a case history

[00:01:28.280]of a project that I’ve,

[00:01:29.850]I’ve actually been working on for about three years now.

[00:01:33.430]I’ve flown a lot of MagArrow surveys on this one,

[00:01:37.380]and then I’m going to conclude my remarks

[00:01:39.660]with some things that I think are important to be aware of.

[00:01:43.570]Before I begin though,

[00:01:44.630]how many in the audience have actually done

[00:01:48.210]drone surveys for mapping geology?

[00:01:51.830]You can raise your hands.

[00:01:53.420]One, two, okay, three.

[00:01:56.180]You guys probably have too.

[00:01:57.420]So how many have done drone magnetic surveys?

[00:02:02.440]Okay, well, hopefully this won’t be real basic for you guys.

[00:02:08.260]Hopefully I’ll give you some information.

[00:02:10.540]For the rest of you, I hope that I’m actually

[00:02:14.950]sharing what I’ve learned in the last

[00:02:17.230]three or four years, doing drone magnetics.

[00:02:22.970]This is my relevant experience.

[00:02:25.916]I claim to be a senior geophysicist and I only claim that

[00:02:30.530]because I’m a senior at this point in my life.

[00:02:33.690]I am a geodroneologist, it’s a word that I made up.

[00:02:40.610]I use drones to map geology. That’s why I made it up.

[00:02:48.900]I’ve done over 30 commercial surveys since I began

[00:02:54.156]in the fall of 2018,

[00:02:56.000]I began actually operating as a commercial service provider.

[00:03:00.250]And I can’t really read my thing here.

[00:03:04.570]I’m collaborating with Seequent and Geosoft

[00:03:07.670]to actually build some tool sets

[00:03:09.530]or they’ll build the tool sets within Geosoft

[00:03:12.400]that’ll make the processing of drone magnetic data

[00:03:17.180]or other data types that are acquired with drones,

[00:03:20.960]at least geophysical data types,

[00:03:22.800]a much more efficient process.

[00:03:25.070]So thank you.

[00:03:27.980]And then at the bottom, in the fine print,

[00:03:29.960]is that fact that I’d been in this business

[00:03:31.960]for more than four decades.

[00:03:34.290]So the benefits of UAV surveys,

[00:03:38.880]the first one foremost is you get a bird’s eye view.

[00:03:41.920]So we can actually acquire multiple data types.

[00:03:45.902]With the drone, sometimes it’s in the same missions.

[00:03:50.770]Sometimes it’s in different missions.

[00:03:53.530]We can access difficult areas with a drone

[00:03:56.560]that you can’t really do very well on the ground.

[00:04:00.250]And in some cases, a conventional pilot airborne survey

[00:04:05.290]is challenging to do with that as well.

[00:04:09.500]We can increase the spatial data density.

[00:04:12.290]I believe that to be one of the strongest reasons

[00:04:15.190]or most important reasons to actually use drone magnetics

[00:04:19.090]or drones in general.

[00:04:21.570]We improve our signal strength

[00:04:23.170]by being closer to the ground.

[00:04:25.670]We can have relatively speaking, a low cost operation.

[00:04:30.310]We enhance the safety of the field staff.

[00:04:34.221]Where they’re not as much at risk because they’re using

[00:04:39.120]essentially an airborne robot to acquire the data.

[00:04:43.780]We reduce the risk to property damage.

[00:04:46.870]These are not big vehicles, they’re not big aircraft.

[00:04:49.180]They don’t really cause a large impact when they crash.

[00:04:53.800]We facilitate temporal change detection.

[00:04:56.980]What that means is that we can fly a survey

[00:04:59.670]and then we can come back at another point in time

[00:05:01.770]and fly it again, and look at the differences

[00:05:03.560]between those two datasets.

[00:05:05.710]I’m speaking in a general sense,

[00:05:07.300]but it’s actually a very useful methodology

[00:05:12.350]for better understanding what’s in terms of geology

[00:05:15.030]or understanding of geological process.

[00:05:19.660]And one of the things that I actually added onto this

[00:05:26.040]for this thing is I do near real time magnetic maps

[00:05:30.550]in the field.

[00:05:31.850]I actually produce a map in the field

[00:05:34.500]almost within moments of actually acquiring the data

[00:05:38.500]with the MagArrow.

[00:05:39.935]So that’s due in large part to

[00:05:43.720]the use of the Geosoft software.

[00:05:46.360]It’s in the field, on my computer,

[00:05:48.250]and I’m actually processing while the guys are flying.

[00:05:54.890]So the limitations.

[00:05:57.810]If you haven’t done a drone survey at all,

[00:06:01.460]I’ll tell you the first limitation is the weather

[00:06:04.550]and wind is not our friend,

[00:06:06.800]but we can actually get around that.

[00:06:10.350]We can wait out the weather and actually fly

[00:06:12.520]when we do have moments of good flying weather.

[00:06:16.710]Site access is a challenge.

[00:06:19.380]Vertical structures like trees, they can be a challenge.

[00:06:23.190]Short duration flights, the drone I use,

[00:06:26.200]I get about 15 to 20 minutes of flight time.

[00:06:29.640]I’m looking at drones that now have hours of flight time.

[00:06:35.320]Small payloads, the drone I use carries

[00:06:38.700]about five kilograms.

[00:06:40.380]I’m looking at drones that actually will carry

[00:06:42.260]up to 20 kilograms.

[00:06:43.390]So I’m looking in the future

[00:06:45.210]that we’re going to be putting more sensors on it,

[00:06:47.430]or different types of sensors that actually way more

[00:06:50.840]than this particular sensor, the MagArrow,

[00:06:53.960]which actually weighs a kilogram.

[00:06:55.410]So we’re not really stressing the drone,

[00:06:58.500]the drone I’m using, with this payload.

[00:07:03.590]And then the aircraft flight characteristics

[00:07:06.030]are our limitation.

[00:07:09.020]The restrictions, and I’m speaking from the U.S. experience,

[00:07:12.780]I know Canada has their own regulations,

[00:07:15.530]very similar to the U.S.

[00:07:16.950]and other countries in the world are

[00:07:18.280]starting to develop a whole series of regulations

[00:07:20.699]to manage drone traffic.

[00:07:23.180]I won’t go through all of that, but the big one

[00:07:25.110]that becomes an issue is that I have to maintain

[00:07:29.890]at this point in time, visual line of sight with the drone,

[00:07:35.410]actually it’s the pilot maintains it so.

[00:07:41.300]So, I put this together several years ago

[00:07:44.030]and what I did it for was, yeah.

[00:07:49.450]To try to explain all the things, all the sensors,

[00:07:51.890]things that we could do with a drone

[00:07:53.860]to help map geology and do other things with it,

[00:07:56.280]from photogrammetry, which is visible light

[00:07:59.230]to infrared, there’s a number of infrared sensors on there,

[00:08:04.870]LIDAR, you probably all know what LIDAR is

[00:08:08.470]and then the geophysics components, which include gamma ray,

[00:08:11.340]magnetics, electromagnetics, and ground-penetrating radar.

[00:08:14.950]I really wanted to get that out there

[00:08:16.630]that we can do a lot more with drones then,

[00:08:20.950]and even it’s even better today, than when I first started.


[00:08:27.850]The MagArrow is that picture on the right there,

[00:08:32.530]on my right, your left.

[00:08:34.630]That’s the picture of my aircraft.

[00:08:37.330]It’s a DJI Matrice 600 Pro

[00:08:40.320]and I suspend the MagArrow,

[00:08:42.330]which is the device that’s hanging below it,

[00:08:48.970]about three to four meters.

[00:08:50.770]What I’m doing is moving it away from the aircraft

[00:08:55.490]so I know I don’t have any electromagnetic interference

[00:08:58.921]in my measurements.

[00:09:04.720]Inside this are two sensors that are cesium vapor sensors.

[00:09:09.172]They’re oriented orthogonally.

[00:09:11.970]That means that this thing has no dead zone.

[00:09:17.300]That’s where the sensors are up here, or is a IMU,

[00:09:22.220]GPS, accelerometers, a gyroscope.

[00:09:25.650]It’s actually measuring the roll, pitch, and yaw

[00:09:27.900]of this aircraft, as well as the position.

[00:09:30.450]I mean, it’s not aircraft, I mean it’s a sensor,

[00:09:33.850]as well as the position of the sensor during the survey.

[00:09:36.780]And that’s the data that I use to position the data

[00:09:40.243]when I map it up, also involved in this front piece

[00:09:44.740]is a wifi, and that’s how we actually communicate with it.

[00:09:48.407]Either with our cell phone or a tablet or computer,

[00:09:51.970]I find so far that it works best for me

[00:09:54.730]to use a Windows 10 computer.

[00:09:59.530]So that’s basically,

[00:10:01.070]everything’s integrated into one package.

[00:10:03.720]It’s not dependent on the aircraft.

[00:10:06.150]So you could actually use this in other environments,

[00:10:10.750]not with a drone,

[00:10:11.670]but you could use it on the ground,

[00:10:13.130]you could use it in a boat.

[00:10:19.100]That’s that.

[00:10:20.990]It’s made by a company in California called Geometrics.

[00:10:25.110]They’ve got some literature up here, if you wish to have it.

[00:10:28.640]So the kinds of projects that I’ve done so far,

[00:10:31.890]I’ve done a bunch of mineral exploration projects.

[00:10:34.160]I’ve worked at high altitude,

[00:10:36.690]or at least where the state’s high altitude

[00:10:38.440]is 12,400 feet above sea level.

[00:10:42.600]I’ve worked in very rugged terrain,

[00:10:45.170]I’ve worked in very tree covered terrain,

[00:10:47.420]very similar to the kind of forest

[00:10:50.450]you have in Eastern Canada.

[00:10:53.090]It was in the U.S. but it was in,

[00:10:56.329]in fact it was in the upper peninsula of Michigan.

[00:11:00.280]I’ve worked in the deserts of the Southwest

[00:11:02.890]in the middle of August, which it’s hot.

[00:11:08.290]So I’ve worked on mine sites, doing mine site

[00:11:12.110]characterization in an active mine.

[00:11:14.720]I’ve done groundwater resource assessments.

[00:11:17.850]I’ve done oil and gas exploration

[00:11:19.690]with some projects with this,

[00:11:22.370]I’ve located a whole bunch of oil and gas wells

[00:11:24.840]using this device.

[00:11:27.450]And I’ve characterized a landfill.

[00:11:30.320]And what I’m going to talk about is

[00:11:32.380]I’ve investigated what is thought to be an impact crater.

[00:11:37.520]It’s a topographic feature,

[00:11:40.890]and I’m going to get right into talking about that.

[00:11:44.200]The crater, we name somewhat affectionately,

[00:11:47.310]Crestone Crater.

[00:11:48.250]It’s just south of the town of Crestone, Colorado,

[00:11:54.242]on the edge of the San Luis Valley.

[00:11:57.797]There we go. Can you see that?

[00:12:01.373]I don’t know how to turn that on.

[00:12:04.310]It’s inside the Great Sand Dunes National Park.

[00:12:08.150]We got special permission to actually fly inside the park.

[00:12:13.740]That’s not something that you normally can get.

[00:12:16.440]The picture on the right, on my right at least,

[00:12:21.430]that’s the actual crater.

[00:12:22.730]It’s about a hundred meters across

[00:12:24.820]and in the sixties, there were some geologists

[00:12:27.373]that came out and looked at it

[00:12:28.640]and they were hypothesized as it being a impact crater.

[00:12:34.130]So it has that kind of feature.

[00:12:36.070]So in the background on that picture,

[00:12:39.660]this, actually this photo was taken from a drone.

[00:12:42.550]The background is the Great Sand Dunes,

[00:12:46.560]in the Great Sand Dunes National Park.

[00:12:48.870]And you can see we’re on a range front,

[00:12:52.750]near a mountain range.

[00:12:55.140]So it was hypothesized to be an impact crater in 1965,

[00:13:00.450]by the Smithsonian geologists.

[00:13:02.820]USGS geologists came out and said they found no evidence

[00:13:06.100]of it being an impact crater,

[00:13:07.920]but the surface sands contain about 4% magnetite.

[00:13:11.950]That was what they reported.

[00:13:14.250]In 2011, the Colorado School of Mines geophysics students

[00:13:18.970]used it as a site for their senior design project

[00:13:22.990]and they did some ground magnetics on it.

[00:13:28.860]It had a magnetic signature

[00:13:30.590]and when I was looking for a place early on in my work

[00:13:33.870]with the prototypes of the MagArrow,

[00:13:36.990]I actually was approached by a group

[00:13:39.530]to be able to fly inside the park service.

[00:13:42.190]And, I mean, inside this national park, and I said, yes,

[00:13:46.470]I’ll come down and we’ll figure out where I can fly.

[00:13:48.660]And this actually popped up.

[00:13:49.880]’cause I knew I could get a response from it.

[00:13:52.350]So in 2017, I did my first drone mag survey.

[00:13:57.090]There was a magnetic high associated directly with that rim

[00:14:01.250]or that berm of that topographic feature.

[00:14:04.520]In 2018, I went back and performed a bigger survey.

[00:14:08.870]Both of those years,

[00:14:09.950]I was using a prototype version of the MagArrow.

[00:14:12.920]In the fall of 2018,

[00:14:14.960]Geometrics released and introduced the MagArrow

[00:14:18.500]at a conference, the SEG conference in the fall.

[00:14:23.250]And since then I’ve performed more than

[00:14:27.261]30 commercial surveys using the commercial version.

[00:14:31.010]And, in 2019, I went back again and I flew that

[00:14:36.010]because I find this a little humorous is that,

[00:14:40.510]every time I got a dataset, I concluded I needed more data.

[00:14:44.830]So you’ll see this in my process here.

[00:14:50.330]So this is the first survey.

[00:14:53.420]And what you see here is I’ve trimmed up the flight lines.

[00:14:56.840]I do all the processing in Geosoft,

[00:14:58.650]so one of the things you do is you,

[00:15:00.570]it runs a continuous, this thing turns on,

[00:15:02.970]you lift it off, it goes off and starts recording.

[00:15:05.930]And when it comes back to the,

[00:15:07.770]it’s recording it on an SD card inside the device,

[00:15:11.000]when it comes back,

[00:15:12.020]we’re actually downloading it over a wifi connection

[00:15:15.190]to our PCs of some type.

[00:15:17.900]And so then we begin the processing of trimming it up

[00:15:22.160]and then making individual flight lines and timelines.

[00:15:25.800]And the background here, this red line,

[00:15:30.468]after the crew got finished,

[00:15:32.150]I hired a crew to come down to fly it.

[00:15:34.602]I went out and collected a ground data set on it.

[00:15:39.050]And I think one of the things is evident

[00:15:40.690]is I don’t walk a straight line.

[00:15:45.360]The drone does a much better job of keeping on target there.

[00:15:51.590]So what we did here is,

[00:15:53.210]it was about a 500 and 500 meter flight block,

[00:15:56.760]20 meter line spacing, 100 meter tie line spacing,

[00:16:00.580]sensor altitude was about 16 meters above the ground level.

[00:16:05.210]I did it in four sorties.

[00:16:07.360]We did it from one location right here.

[00:16:09.660]That’s actually the shot of the pilot

[00:16:11.940]and the drone, the prototype version.

[00:16:15.020]This gentlemen here is a geologist

[00:16:16.440]for the National Park Service.

[00:16:17.740]He was very curious of what we were going to do.

[00:16:20.070]And at the time that we completed that survey

[00:16:22.330]was less than four hours.

[00:16:23.970]The guy showed up at eight o’clock in the morning.

[00:16:26.180]They flew it, finished it up,

[00:16:27.627]and they were out of there by noon.

[00:16:29.890]I then went out and spent the next four hours

[00:16:31.910]collecting this ground data so.

[00:16:35.950]But what’s it look like?

[00:16:37.750]Well, the bigger survey is the drone mag data.

[00:16:42.650]And this is really as raw data as I got,

[00:16:48.130]I haven’t done a lot to actually improve the data.

[00:16:53.380]The interior survey, interior color contours,

[00:16:57.340]are from my ground mag survey.

[00:16:59.570]What I was doing here, I was just trying

[00:17:01.500]to see a comparative study between,

[00:17:04.100]trying to compare what I was able to get

[00:17:05.820]with the prototype of the MagArrow

[00:17:08.230]and what I could get on the ground

[00:17:09.680]with a cesium vapor magnetometer, a ground-based one,

[00:17:13.430]that’s used often for mineral exploration, and I was able,

[00:17:16.850]you can see that I have this circular feature here.

[00:17:19.570]I also have something going on here,

[00:17:22.310]and I have a few more circular features.

[00:17:24.730]There’s something here that’s actually distorting

[00:17:26.817]the field a bit.

[00:17:29.470]Well, the conclusion at the end of that survey was

[00:17:33.560]I needed more data.

[00:17:36.120]So, but this is the vertical derivative

[00:17:39.970]of the drone mag’s survey.

[00:17:42.700]These features right here became very interesting to me

[00:17:45.210]because we just started studying this one,

[00:17:48.510]but we’re starting to see these other circular features,

[00:17:51.840]which kind of raised a few questions.

[00:17:56.390]So in 2018, I went back with a second generation prototype

[00:18:01.290]and we flew a square mile.

[00:18:02.750]This is 1.6 kilometers. That’s 1.6 kilometers.

[00:18:08.220]We have multiple locations where we lifted

[00:18:11.530]and did our survey from, at that time, my thinking was,

[00:18:14.900]I’d had to do these flight lines

[00:18:16.830]to the north, the bottom, the middle.

[00:18:18.970]We flew those blocks

[00:18:20.810]and then we came down and flew these blocks.

[00:18:23.320]And then we moved our pilot around

[00:18:25.860]to be able to maintain visual line of sight.


[00:18:34.430]So we did 25 sorties, a 40 meter line spacing,

[00:18:38.630]200 meter tie line spacing, 25 meter AGL,

[00:18:43.020]21 meters, that’s for the altitude for the aircraft

[00:18:45.330]and 21 meter AGL for the sensor.

[00:18:48.990]We flew a square mile and it took us a day and a half.

[00:18:56.080]Part of what I’m actually expressing

[00:18:58.030]and you’ll see here is

[00:18:59.430]how over the course of the last three years,

[00:19:02.370]and actually the introduction of this device,

[00:19:04.620]which was much easier and much more easy to use

[00:19:07.660]then the prototype we’ve actually improved

[00:19:10.330]our productivity significantly.

[00:19:12.670]So this is the data from that 2018 survey.

[00:19:16.520]And we now have the Crestone Crater.

[00:19:19.230]You see this low here, note this low up here.

[00:19:21.730]We would never have seen that in that first survey,

[00:19:24.590]I’m pointing that out because that’s actually

[00:19:26.580]a significant feature I’ll explain later.

[00:19:29.160]And then we had this thing here,

[00:19:31.540]which I thought was at the time

[00:19:33.510]might’ve been some sort of intrusive.

[00:19:36.250]It turns out that it’s actually a piece of cretaceous

[00:19:39.430]that has been uplifted from the valley floor.

[00:19:43.120]I’m not sure what the mechanism was,

[00:19:45.040]but the geologists at the,

[00:19:47.890]I don’t know why the, it’s actually a shale unit.

[00:19:51.250]I don’t know why it’s more magnetic,

[00:19:53.300]but yeah, that’s what the geologist

[00:19:56.780]at the Park Service shared with me.

[00:19:59.360]So here we did a high pass filter.

[00:20:02.451]I had a colleague actually do that processing on this,

[00:20:05.600]and then I’d run a quick interpretation on it.

[00:20:08.260]We did a reduce to pole.

[00:20:09.960]So that’s from that data set.

[00:20:11.680]What we’re trying to do is isolate the anomalies

[00:20:13.670]and look for the features that become significant

[00:20:16.100]for our understanding of what the mag is telling us

[00:20:19.100]regarding the geology.

[00:20:22.150]And that’s the presentation of it

[00:20:23.640]sitting on top of a Google Earth.

[00:20:25.770]So you can see we’re on the range front.

[00:20:28.690]And at the end of the day, I concluded,

[00:20:32.500]I just didn’t have enough data so.

[00:20:36.940]There’s a theme here.

[00:20:39.070]So in 2019,

[00:20:42.563]I went back to,

[00:20:44.480]I also realized I hadn’t really use the

[00:20:47.500]commercial version of the device,

[00:20:49.530]which had changed a bit since my first use of it.

[00:20:52.870]I went back and I actually tried to replicate

[00:20:56.250]as much as I could, the original first two surveys.

[00:20:59.820]And then you’ll see that I actually expanded that,

[00:21:03.650]my aerial coverage significantly.

[00:21:06.220]So the first survey kind of the first one,

[00:21:09.090]this is sort of a 10, this is 10 meter line spacing we did.

[00:21:14.120]This is the difference between 2018 or 17 and 2018.

[00:21:19.280]We did it in three flights,

[00:21:20.670]back then we did it in five flights.

[00:21:23.180]We did it from basically the same position.

[00:21:26.390]That’s the color contour

[00:21:27.960]sitting on top of a digital elevation model.

[00:21:30.360]It’s a one meter digital elevation model

[00:21:32.860]that the USGS has for this service for this area.

[00:21:37.640]Notice that we have a couple other types of features.

[00:21:40.310]I didn’t actually see these earlier on,

[00:21:42.520]but now that we’re actually getting more,

[00:21:45.500]higher definition data sets,

[00:21:47.020]I’m beginning to see these things

[00:21:48.390]that we just didn’t know were there.

[00:21:51.660]So this is the second 20 meter line spacing.

[00:21:58.400]Launched from the same point

[00:22:00.210]and basically we’re doing four sorties on this one.

[00:22:04.750]All of that took us, both of those surveys,

[00:22:06.840]took us about a day to complete,

[00:22:09.740]and we have very similar response to what we had in 2018.

[00:22:13.380]So we know the geology hasn’t changed on us in the meantime.

[00:22:19.250]So and then we went and took a bigger view.

[00:22:22.700]And the bigger view is we did a

[00:22:26.100]two and three quarter square mile survey.

[00:22:30.150]That’s what ultimately ended up being.

[00:22:32.320]Did a 100 meter line spacing, 400 meter tide line spacing,

[00:22:36.090]25 meter AGL, 20 for the aircraft, 21 for the sensor.

[00:22:42.130]It took us basically less than two days

[00:22:44.410]to acquire all that data,

[00:22:46.280]but the key point is we did it from one location.

[00:22:49.830]We were limited by the park service

[00:22:51.760]from just being in one spot.

[00:22:53.600]So we developed a methodology that allowed us,

[00:22:56.600]our pilot to maintain visual line of sight

[00:22:59.330]with the aircraft.

[00:23:00.590]The other thing is that these are mile long,

[00:23:03.500]two mile long flight lines.

[00:23:05.730]So we were able to increase our production.

[00:23:08.660]Using part of it, had to come

[00:23:10.120]when the technology was better

[00:23:11.460]and part of it came from the fact

[00:23:13.780]that we knew how to do it a lot better than we did in 2017.

[00:23:22.370]So what did I get from that?

[00:23:23.910]Well, on the, your left is the mag map

[00:23:27.920]and yes, these features still come through,

[00:23:30.544]we got better definition on this one.

[00:23:33.380]Now we’re seeing some structure coming in there,

[00:23:35.930]and this is actually going into the valley.

[00:23:38.140]I know from some seismic data that a friend shared with me

[00:23:41.270]that actually that is a down drop walk

[00:23:44.400]that’s up against the range front.

[00:23:47.480]And then I just did a quick interpretation of it

[00:23:49.970]to be able to say, I’ve interpreted these faults.

[00:23:53.660]I’ve interpreted those as grabens.

[00:23:57.420]Why that’s important and I’m going to say that

[00:24:00.210]we’re not seeing the actual Crestone Crater,

[00:24:02.360]but this survey was never designed to do

[00:24:04.200]the Crestone crater to actually map it.

[00:24:07.050]The first surveys were.

[00:24:10.770]This one was really to try to get the bigger picture,

[00:24:12.980]to get the better idea of where the structures were.

[00:24:16.208]And the reason for that,

[00:24:19.120]I’m going to give a little summary here.

[00:24:22.480]The 2017,

[00:24:24.230]the circular magnetic anomaly directly associated

[00:24:27.300]with the berm appears to be due to a magnetite content

[00:24:31.090]within the berm.

[00:24:32.660]Now, remember that the sands above the crater

[00:24:37.660]in this area are 4% magnetite.

[00:24:41.700]Why is there an increase in magnetite concentration

[00:24:44.630]at the berm, that’s one question.

[00:24:46.660]Are there other circular features of a similar origin,

[00:24:49.330]why are they existing? That was another.

[00:24:51.140]We saw that in our first data sets.

[00:24:53.620]2018, we indicated we were starting to see these two,

[00:24:59.180]these graben features and that they’re offset.

[00:25:02.040]And if they’re offset,

[00:25:03.050]they’re probably faulted and shifted over.

[00:25:06.530]So we think there was movement along that fault.

[00:25:09.910]That back in the day, paleo earthquakes along the fault

[00:25:13.650]may have created sand boils.

[00:25:15.830]Now you’ve got to realize that even today

[00:25:19.040]that is a known active fault system.

[00:25:21.310]So there are earthquakes all the time.

[00:25:23.920]Also back before people started populating

[00:25:26.740]the San Luis Valley,

[00:25:28.140]there was a very high hydraulic head

[00:25:30.650]in the groundwater so that the early settlers

[00:25:33.610]could walk out almost anywhere in the valley

[00:25:35.860]and all they had to do is poke a pipe in the ground

[00:25:37.990]and they got a little bit of a water geyser coming up.

[00:25:40.900]So they were able to essentially get artesian wells

[00:25:44.550]because the valley was actually doing, it was good.

[00:25:49.660]Now they’ve pumped it down a lot since then,

[00:25:51.240]so you’d never see that today.

[00:25:53.050]But what we think happens is that

[00:25:55.330]there was some paleo earthquakes

[00:25:57.003]that had enough energy to actually start

[00:26:00.570]causing some little geysers

[00:26:03.050]or little fountains of sand boils,

[00:26:06.740]bringing coarse-grained material from below

[00:26:10.000]and depositing it on the surface.

[00:26:12.330]And then in filling it with the sand,

[00:26:14.070]the magnetite rich sands.

[00:26:16.130]So that’s our current explanation of it.

[00:26:20.350]There are those that don’t believe that that,

[00:26:22.250]well, they haven’t probably heard this one yet,

[00:26:24.530]but there are those that still can think

[00:26:26.520]that this is a impact crater

[00:26:28.057]and there are those that think

[00:26:29.620]it’s just a windblown feature.

[00:26:34.330]So, but important to know is that because of this data,

[00:26:38.870]I actually have provided this data to a geophysicist

[00:26:45.034]at the USGS, who was curious about

[00:26:47.700]what is the source of these anomalies

[00:26:50.350]that he’s seeing in their air mag data over this area.

[00:26:54.440]And he thinks that it’s due to magnetite

[00:26:57.710]and we’re just seeing a topographical response.

[00:27:01.290]So I’ve given this data to him, we’re actually modeling it.

[00:27:04.790]So what we think is, let me back this up a little bit here,

[00:27:11.290]these features right here are all following,

[00:27:14.670]they’re low grade magnetic anomalies,

[00:27:16.850]and they’re all somewhat associated with topography.

[00:27:20.420]So what we think is that we do get a bit of a concentration

[00:27:24.050]of the magnetite rich sands

[00:27:26.000]a lot that is associated with topography.

[00:27:28.630]And that a lot of that response, not the graben response,

[00:27:33.450]but a lot of that other response

[00:27:34.790]is essentially noise sitting on top of our base level data

[00:27:41.500]due to the magnetite.


[00:27:47.160]conclusion, by applying different scales

[00:27:50.030]of UAV magnetic surveys from very high definition,

[00:27:54.650]which is the very tight space stuff to high definition,

[00:27:58.930]we have gleaned some new insights into geological structure

[00:28:01.760]leading to the conclusion that the Crestone Crater

[00:28:04.220]is most likely due to a sand boil.

[00:28:07.610]In addition,

[00:28:08.443]the magnetic data are reshaping our thinking

[00:28:10.720]about the groundwater recharge into the San Luis Valley.

[00:28:14.030]This is an agricultural area that has been over pumped,

[00:28:18.590]and it is very much a concern for the valley

[00:28:21.240]of how they’re managing our groundwater resources.


[00:28:28.040]Additional remarks.

[00:28:29.610]I’m not without additional remarks.

[00:28:32.710]First off,

[00:28:34.010]I want to point out weather is always the challenge

[00:28:36.110]that we’re up against most drone surveys,

[00:28:38.790]access to flight operations, staging locations.

[00:28:42.430]It’s an acronym I call a fossil.

[00:28:45.090]I hope that you will find that humorous, can be a challenge,

[00:28:49.950]locating where the pilot is can be a real challenge.

[00:28:53.340]Drones work well when the terrain is rugged

[00:28:56.060]or covered with wetlands,

[00:28:58.530]they also work in areas that aren’t rugged

[00:29:02.037]or covered with water.

[00:29:04.350]UAV magnetic surveys are scalable to fit the objective.

[00:29:07.360]That’s actually one of the points

[00:29:08.500]I want to really drive home is that

[00:29:10.360]because of the very portable and very flexible nature

[00:29:14.920]of actually designing and executing a survey,

[00:29:18.620]we could fly a survey with,

[00:29:19.930]let’s say a hundred meter line spacing

[00:29:21.990]and identify a feature that we want to get more detail on

[00:29:25.170]and immediately go in and actually fly a survey

[00:29:27.440]at 20 meter line spacing and maybe even lower.

[00:29:30.550]So that’s one of the real operational advantages

[00:29:34.236]of flying a drone magnetic survey.

[00:29:37.600]Drones are capable of longer flights are needed.

[00:29:40.720]Most of us in the business know that

[00:29:42.290]they’re actually coming to the market now,

[00:29:43.840]there’s commercial ones available,

[00:29:45.560]and some people build their own.


[00:29:48.543]but the current UAV that, the one that I’m using

[00:29:51.210]it does a really good job of getting it done

[00:29:53.640]and it’s at a price point that a lot of folks can afford

[00:29:56.280]to be in the business, but other sensors are needed.

[00:29:59.560]Other geo-physical sensors are needed.

[00:30:03.246]I’m learning about a few EM sensors

[00:30:05.500]that are now coming to the market

[00:30:07.320]or coming to folks have built them

[00:30:09.210]and they’re now available or will be available

[00:30:11.500]for commercial surveys.

[00:30:16.060]Let’s see, what else is there?

[00:30:18.380]Oh, this is the question of the day.

[00:30:21.070]Why do meteors always land in craters?

[00:30:25.950]Thank you for laughing at,

[00:30:27.260]I paid these guys to laugh at that, by the way.

[00:30:31.510]The next thing is

[00:30:33.130]I have been involved with

[00:30:39.909]the near surface technical section of the SEG.

[00:30:42.610]They are putting on a drone workshop at the SEG meeting

[00:30:49.210]this fall, it’s called Summit on Drone Geophysics.

[00:30:53.800]And it’ll be October 16th at the George R. Brown

[00:30:58.130]in Houston, Texas,

[00:31:00.070]I’ve actually talked to a number of the folks here

[00:31:03.000]who are going to come down and actually present

[00:31:05.343]in that workshop.

[00:31:07.700]There’ll be more coming if you want to get on my

[00:31:10.330]emailing list and let know about it,

[00:31:12.270]just give me your card and I’ll keep you apprised of it.

[00:31:16.600]So finally, thank you for your attention.

[00:31:20.360]You’ve been a great audience.

[00:31:22.310]I’ve got to work on my material

[00:31:23.810]and get a little bit more humor into it, but

[00:31:26.376]you’ve been a great audience and thank you very much.

[00:31:29.830]If there are any questions at this point.

[00:31:31.472](audience clapping)