What Miners Want

I attended the Commercial UAV Expo in Las Vegas at the end of October.  I gave a talk entitled “Mine Site Mapping – One Year In.”  This talk was on our experiences with performing mine site mapping services with our AirGon Services group.   Our services group is primarily about Research and Development (R&D).  We use our engagements with mining companies to discover the products that they need, accuracy levels and, most of all, how to reliably create these products.  These experiences inform both the development of our technology (the MMK, Topolyst, Reckon, the BYOD Mapping Kit) but also help us develop best practices for both collection and processing.

As I prepared for this presentation, I reviewed the mine site mapping projects we have performed over the past several years to tabulate the products our customers have requested.  These turned out to be, in decreasing order of popularity:

  • Site Volumetrics with a priori base line data
  • Site Volumetrics with no prior data
  • Site contours (“topo”) – 2 foot interval
  • Site Contours – 1 foot interval
  • Time series volumetrics (“borrow pit”)

In every case, the customer desired a site orthophoto.  In fact, they usually want an ortho of the entire site with analytic products of a subsection of the mine site.

I thought in this month’s section, I would review these products from the acquisition and processing point of view.

 Volumetrics with baseline data

I have written a few articles about injecting a priori data into a mapping project.  This is the situation where, at some time in the past, the customer has done a site survey and wants to use these data as the bottom surface of stockpiles.  Their primary desire here is for consistency from inventory to inventory.

An example of this, a large limestone quarry that we fly, is shown in Figure 1.  Here baseline data as well as a reclaim tunnel model have been provided to us as a DWG data set.  The illustration of Figure 1 shows these data being used by Topolyst to create a 3D base surface.

 

Figure 1:  Bottom Data with reclaim tunnel model

Figure 1: Bottom Data with reclaim tunnel model

The primary challenge that we have when receiving a priori data is the accuracy of the data.  We often find that these data were obtained by traditional stereo photogrammetric collection techniques so we do not have a point cloud from which to assess accuracy.  Now, done properly, stereo photogrammetry produces survey grade data.  Unfortunately, much of this a priori data was collected with the surface obstructed by existing stockpiles; in other words, it was not a stockpile free base data mapping.  This means that the stereo compiler had to estimate locations under the existing data.  We find that in most cases, these estimations are simply linear interpolations from one side of the obscured area to the other.  We often find these bottom models extending above the current surface.  It is difficult to tell if the data were incorrectly modeled or if the ground has actually changed from the time the baseline data were collected.

A second big challenge we have with these data are a lack of knowledge by the provider as to the exact datum to which the data are referenced.  We are often concerned with elevation differences of just a few centimeters.  The Geoid model really matters when you are approach survey leveling accuracy goals.  We have found, on more than one occasion, a priori data with an incorrect vertical model.  This usually occurs (at least in the USA) as a result of using the incorrect NAD83 to WGS84 transformation.

Over the past year, we have added a lot of refinements to how Topolyst handles this a priori data.  Those of you who do LIDAR or photogrammetric processing will immediately recognize this as the problem of introducing “breaklines” and “mass points” into a model.  LP360 (Topolyst is just a variant of LP360) has always been a very strong product in terms of breakline modeling.  We have added a few features in this area to improve the modeling as it typically applies in UAS mapping.  We are now at the point where we really do not have any software issues with this sort of modeling but the interpretation problems will always remain.

This type of modeling requires:

  • Direct geopositioning (RTK/PPK) on the drone
  • Multiple surveyed check points on the site for data validation
  • Strong modeling tools such as Topolyst
  • A conference or two with the customer to understand the models
  • A lot of patience when defining stockpiles

Volumes with no a priori data

Here the customer is interested only in the volumes of the piles, without regard to location.  The deliverable is generally a spreadsheet with volume, material type, density and tonnage.  Of course, our customer deliveries are via our cloud data platform, Reckon, so we want the toes to be correctly georeferenced.

If you leave out the correct georeferencing (meaning you compute the volume of the pile but do not necessarily try to align it with an existing map), you have the sort of processing offered by a myriad of web-based solutions such as Kespry.  Under this business model, you typically upload the raw drone images which have been georeferenced by the navigation grade GNSS for x, y and the drone barometric altimeter for elevation.  This typically provides horizontal accuracy on the order of several meters and vertical accuracies at about 5 meters.  So long as the camera is properly calibrated, this methodology leads to volumetric accuracies that are accurate to within about 5%.

We never do these projects without some check points.  These are surveyed image identifiable points that we use to check horizontal and vertical accuracy.

The biggest issues we have encountered with this type of project is the definition of the stockpile toe – it is somewhere between comingled piles, it traces along an embankment such as the pit, the stockpile is in a containment bin and so forth.   There requires a lot of careful toe editing in a three dimensional visualization environment such as Topolyst.

We never have issues with accuracy because we always fly with a direct geopositioning system.  For our MMK, it is a Post-Process Kinematic, PPK, GNSS system.  For the senseFly eBee, it is an onboard RTK system.  We always lay out some checkpoints for project verification.

A very clean mine site with stockpiles sitting on a surface is nearly non-existent (except in our dreams).  While you sometimes encounter sites where you can just manually draw a toe, these sites are nearly always at inventory transfer locations, not working mines.  In fact, of all the mine sites we have surveyed, we have encountered only one “groomed” site (see Figure 2).  Even at this site, the upper left and lower right piles required some disambiguation (wow, that’s a big word!) work to separate the pile edge from encroaching vegetation.

Figure 2: A "groomed" inventory site

Figure 2: A “groomed” inventory site

 Site Contours (“topo”)

A surprising number of customers want contours.  As you know, these are elevation isolines at a particular interval.  Most customer want either 2 foot or 1 foot contour intervals.  These data, in DXF or DWG format, are used as input to mine planning software.  I find this a bit odd since I would think by now that this downstream software would directly ingest a LAS point cloud or at least an elevation model.

Contours are always absolutely referenced to a datum (a “Network”).  This can be a local plant datum or, much more commonly, a mapping horizontal and vertical datum such as a state plane coordinate system for horizontal and NAVD88 with a specific geoid model for vertical (at least in the United States).

You can tie to the datums using either direct geopositioning with onboard RTK/PPK or you can use dense ground control points.  I personally would never collect data that must be tied to a datum without having a few image identifiable checkpoints.  Unfortunately, this means that you will need at least an RTK rover in you equipment kit.

A good rule of thumb for contours is that the accuracy of the elevation data should be at least three times the accuracy of the desired contour interval.  This says if you are going to produce 1 foot (30 cm) contours, you need 4” (10 cm) of vertical accuracy relative to the vertical datum.  When you measure your checkpoints, don’t forget to propagate the error of the base station location (which you might be deriving from an OPUS solution).

Preparing a surface for contour generation is perhaps the most tedious of mine site mapping work.  It is generally the only site mapping you will do that requires full classification of ground points (the source for the contour construction).  An example of 2 foot contours within a mine site is shown in Figure 3.

Figure 3:  An example of 2' contours

Figure 3: An example of 2′ contours

Sites with a high degree of vegetation in areas where the customer wants contour lines will have to be collected with either manual RTK profiling (very tedious!) or with a LIDAR system.  You simply cannot get ground points with image-based Structure from Motion (SfM).  No surprise here – this is why LIDAR was adopted for mapping!

If the customer does not want to pay for LIDAR or manual RTK collection, the vegetated areas should be circumscribed with “low confidence” polygons.  You can either exclude the contouring completely from these areas or classify the interior to vegetation and let the exterior contours just pass though the region.  In any event, the customer must be aware that the data are quite inaccurate in these regions.

The SfM algorithm gets quite “confused” in areas with overhead “noise” such as conveyors and vegetation.  This confusion (actually correlation errors) typically manifests as very low points.  You will need to find and clean these points prior to contour generation.

Conclusions

Product generation for UAS mapping requires a lot of front-end planning.  This planning needs to be product-driven.   If you customer (you, yourself, perhaps) needs only volumes with no tie of the toes to a datum, you can get away with no control so long as some other information such as camera calibration and flying height are correct.  By the way, we recommend never collecting this way since you are precluded from doing any meaningful time series analysis.

On the other hand, most meaningful data (that is, you can quantify the accuracy relative to a datum) will require a very careful control strategy as well as a rigorous processing workflow with the right tools (meaning Topolyst, of course!).  No matter what geopositioning strategy you employ, you should always have some independent methods for verifying accuracy.

If all of this seems a bit daunting, you can get assistance from us.  Remember, our services group is really our R&D lab.  Our real goal is to sell technology to owner/operators and production companies.  No matter what drone you are using, you can always avail of our consulting services.  We have gained a lot of experience over the past few years, mostly by first doing the wrong thing!  Save yourself this time and money by engaging with us!

 

 

 

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3DEP, LP360 Toolbox and AirGon

I am looking for the month of May – it seems to have disappeared without a trace!

We recently visited with the Tennessee Office of Information Research (OIR) in beautiful Nashville, Tennessee. The OIR is the coordinating state agency for a USGS 3DEP LIDAR (3 acronyms in a row – not quite a record!) acquisition project. Under this program, the state of Tennessee will be flown at Quality Level 2 (2 points per square meter) over a four year period. The initial collection (slated for this fall) will encompass some 11,500 square miles, covering 27 counties.

3DEP is an excellent opportunity for state and local government agencies to pool their financial (and often technical) resources to obtain point cloud data. By spreading the cost across a spectrum of stakeholders, a surprisingly large amount of data collection can be accomplished.

Our discussions with the OIR led naturally to a conversation about how LIDAR data are used in GIS and engineering departments. We covered the usual suspects such as flood plain analysis, basic 3D visualization, site planning and so forth. By the end of the conversation, I was convinced (as usual) that every single state and local government GIS workstation should have access to a current image and current 3D (e.g. LIDAR point cloud in LAS format) backdrops. Why would anyone find it acceptable to be without a cross-sectional view of their municipal data on an ad hoc basis? Mainly because they have never had this level of information available. You never miss what you have never had!

When we returned to the office, we decided to put together, once and for all, a package of material for folks who are either contemplating acquiring LIDAR data or those who have access to LIDAR data. We will develop use cases and return on investment information for the range of applications that make sense for these data. If you have some novel ideas and particularly case studies, please work with us. Obviously we want to sell more software but we believe a rising tide lifts all boats. We need to get the tide (meaning the understanding and effective use of LIDAR data) rising first!

Speaking of software, we hope to have our experimental release (EXP) of LP360 available for download by the end of this month (June). The developers are doing fine. It is me who always throws a wrench in the delivery schedule – “let’s get return selection added to the new Live View dialog before we release…” Speaking of Live View, this is a new dynamic filter in LP360 that lets you change class, return and flag filtering on the fly. You are really going to like this new feature!

While we try to make features in our tools easy to use, the LIDAR tools on the market still tend to be toolbox oriented rather than workflow specific. For this reason, it is very important to participate in training if you hope to realize a maximum return on your investment. We offer a range of training (and consulting) from web based to on-site. In addition, we have our Huntsville-based LP360 training coming up in the fall.

On the AirGon side of things, we have been talking to a lot of potential clients who can make immediate use of small Unmanned Aerial Systems (sUAS) mapping. We offer a complete helicopter-based metric mapping kit in the AV-900 MMK. This is garnering a lot of interest since it provides a turn-key solution of hardware, software and training for doing jobs that have an immediate high return on investment such as stockpile volumetric analysis. However, we also offer just the piece parts for those who wish to assemble their own system. For example, if you have decided on a small wing type sUAS such as the eBee from SenseFly, LP360 for sUAS is still your best option for extracting volumetrics (anyone who has tried to do a multi-pile site using the point cloud generation software shipped with these systems will readily agree!). In addition, AirGon Reckon is the best product in the market for hosting and delivering mine site orthos and volumetric reports. By hosting our volumetrics delivery system in Amazon Web Services, we relieve you the need to worry about data delivery to multiple offices, data backup and security.

Summer promises to fly by just as quickly as the spring. We are attending a number of conferences such as the ESRI meeting and the Transportation Research Board AFB-80 summer meeting. If you are attending one of these, please look us up. See you in July!

Drones, Metric Mapping and RTK

We have been very busy this first third of 2015 with software development (as we always are).  The thing about software is that it is never static.  It is either undergoing new additions or entering the end of life phase.  We have had a very big focus on ensuring that our products are optimized for LAS 1.4 support as this is the new requirement of the USGS.  Additionally, we like to use LAS 1.4 in our mine site workflows since it supports a few nice capabilities that were not in LAS 1.3.

This is definitely the year of the drone.  Every major geospatial hardware firm has announced a drone system for remote sensing (some for metric mapping).  While the USA is inching along toward some usable drone rules, other countries have clear rules in effect and drone mapping is becoming a standard survey/mapping tool.

We are garnering a very high interest in AirGon’s Metric Mapping Kit (MMK).  This solution provides everything you need to do uncontrolled mapping projects using a small Unmanned Aerial System (sUAS) except a processing laptop computer.  Add in your own surveyed control points to reach survey grade accuracy.

Speaking of the Metric Mapping Kit, we will be hosting a AV-900 MMK workshop in Toronto, Canada on June 11th and 12th.  Thanks to Jim Giordano, we will be presenting live flight demonstrations at VicDom Sand & Gravel as well as an in-depth look at mission planning and post-collection data processing.  Our focus will be on drone-collected volumetrics. Personal protection equipment (steel toed boots, hardhat, safety vest and safety glasses) are required.  Remember that a passport is required for travel between the USA and Canada.  Space is extremely limited so sign up early!

We have been (in a joint project with Applanix, a Trimble Company) researching the use of Post-Processed Kinematic (often erroneously called Real Time Kinematic, RTK) control solutions.  Obviously everyone flying a sUAS for metric mapping purposes would like to dispense with the tedium of deploying ground control.  We will publish the results of our efforts as a white paper when the work is complete.  My goal is a recipe, if you will, of the methods that are appropriate for a given desired accuracy level.

We will be posting an experimental (EXP) release of LP360 (all license levels) within the next few weeks.  Those of you on software maintenance will be able to download this release via the “Check for Updates” option under LP360 Help.  There is a separate article in this newsletter that provides a highlight of the new features.

Till June – Best Regards,

Lewis

GeoCue Group News – May 2015

April 2015

We’ve had a very busy first quarter with many road trips and demonstrations of technology. I continue to remain very excited with respect to small unmanned aerial systems (sUAS or drone) technology. Applied to the right sort of problem, this is a real game changer.

We just attended the SPAR conference in Houston last week. SPAR is a conference with a primary focus on tripod (static) laser scanning and secondary foci on mobile laser scanning and an emerging section on sUAS technologies. The conference was attended by perhaps 1,000 folks. We were exhibiting as AirGon in the UAS section of the exhibit hall. If you are involved in building information management (BIM), this is a must-attend conference.

I made an interesting observation regarding the emergence of sUAS technology for mine site mapping.  It reminds me a lot of the years when tripod laser scanning was emerging and replacing total station surveys in brown field as-built documentation projects. sUAS mapping is the logical choice for volumetric mapping at mine sites. While it has some disadvantages, its pluses put it ahead of any other technique for this sort of application. For the first time, I encountered service providers who are using other approaches to solve this problem. Many of those who are using tripod scanning for volumetrics feel threatened by this newly emerging technology. Who can blame them? If I had just invested 80K in a laser scanner for volumetrics and then observed a technology much more suited to the task, I would be defensive as well! Thus I am seeing end-users (e.g. mine owners) as the parties most embracing of sUAS mapping with service providers being drug into the space by their customers. This is, ironically, not unlike the situation when tripod laser scanning was emerging. Service providers had big investments in total stations and had no burning desire to have to invest in a new technology.

We are changing our newsletter a bit with this issue. We will now be hosting information such as our tool tips and how-to articles in our new GeoCue Group knowledge base. We will put a lead-in sentence in this newsletter that will link you to the knowledge base article. This will be a real benefit as time goes on. The Knowledge Base includes a robust search capability and consolidates all of this rich information in one spot. This means that if you need to review our extensive past article on breaklines, you can simply search the knowledge base rather than digging through the newsletter archive. We are gradually moving all of the past technical articles over to the knowledge base.

We continue to focus a lot of our development efforts on LP360. These developments range from ease of use to advanced methods for creating the toes of stockpiles for volumetric analysis. In addition, we have been tuning our display subsystem to increase window refresh times and reduce our memory footprint. Finally, we are adding (to the Standard level) a new point cloud task for cleaning up areas where batch ground classification did not quite do the job.  We will be posting an “Experimental” release of LP360 within the next several weeks that provides initial versions of these features.

Thanks very much for being a GeoCue Group customer or an interested observer! See you in May.

Best Regards,

Lewis

GeoCue Group News – April 2015

The Worst Decision is No Decision

In business, the easiest decision when faced with a multifaceted problem is no decision at all. Unfortunately, it is often the worst decision. The world marches on, not caring about your inability to decide. You are at the winds of fate rather than taking an active hand in shaping your destiny.

I think this is the case with the Federal Aviation Administration (FAA) and small, unmanned aerial systems (sUAS). Hiding behind a front of “air safety” and “complex problem”, the FAA has chosen to make no decision at all. Meanwhile, most of the rest of the world is well into the second generation of integrating sUAS into the commerce infrastructure.

While the FAA says that it is minding safety and will not make a decision until all the i’s are dotted and the t’s crossed, this cannot actually be the true reason for a lack of rules. Within the existing framework of admittedly very fuzzy FAA rules, it is perfectly legal for the farmer’s daughter of age 10 to fly a 40 pound drone over the 1,000 acre farm, collecting as much data along the way as she desires. It is her hobby. However, the FAA says that it is illegal for the farmer herself to fly this same sUAS if the purpose is collecting data to improve yields or any operation that is revenue generating (yet another really fuzzy boundary). Let’s see now; if I am a non-professional doing this simply as a hobby, it is perfectly safe. If I am a professional who has devoted business investment into the effort, it is inherently dangerous. Of course this is an absurdly ridiculous situation and everyone involved in drones is quite aware of the fact that the lack of realistic flying rules for drones is as issue of bureaucratic morass rather than safety. My own opinion is that no one at FAA wants to be the person who signed a paper that might somehow surface in an accident investigation. And, yes indeed, there are and will be many, many sUAS accidents!

I posit that this lack of simple and sane rules from the FAA is actually endangering the airspace. The genie is out of the bottle; on any given day, thousands of sUAS take to the air in the United States in a vacuum of simple safety guidelines. It is a lawless environment with participants ranging from those very aware of safety rules (think surveyors doing volumetric data collection over coal mines in West Virginia) to kids flying high end multirotors over crowded sidewalks (oddly, one can make a pretty sound argument that the surveyor is the person on the wrong side of the law!).

The recent FAA exemption for six companies doing aerial videography gives us a preview of what may be coming. Rather than a very simple set of rules focused on safety, the operating regulations for these guys reads like the ground prep for a moon shot. Now admittedly, the folks applying for the waivers threw everything including the kitchen sink into their request for waiver but the FAA, rather than crossing off many of the proposed items for the sake of simplification, said instead “this looks sort of good but we need to add this big list of additional requirements…..”

What we need are some very simple rules that will set the guidelines for folks who are going to fly drones, regardless of the regulatory environment. Why not ask them to abide by some very straightforward guidance that will help ensure the safety of persons on the ground. After all, the real safety threat from sUAS flying close to the ground (say 130 meters and below) is the drone falling from the sky and hitting someone on the head. This is the approach that has been taken by many leading aviation nations such as Canada and the United Kingdom. No onerous, irrelevant requirements for manned aircraft private pilots licensure and FAA airframe certification but simple rules that aim at keeping altitudes such that threats to manned aircraft are avoided and a big focus on protection of persons who might be below the aircraft.

Oh well, I think I wish for too much. In our current political environment, common sense is in very short supply!

sUAS – Where will this business go?

The small Unmanned Aerial Systems (sUAS) business is very appealing. For less than US $20,000, you can outfit a complete system for collecting aerial imagery and processing the data into an array of high quality mapping product.

But who will roll out these new low cost mapping systems?  Will it be the major airborne acquisition companies?  Perhaps, but with a business model predicated on large collects, does this fit?  Will it be the owners of the sites that require mapping such as quarry owners, land developers, coal fired power plants?  Or will it be professional land surveyors who offer sUAS mapping as another tool in their toolbox?

In my mind, the professional surveyor is best equipped to roll out this new business tool.  The PS is already tuned to a business model of travelling to small sites, collecting  data, processing results and consulting with the client.  The sUAS will provide a new tool that will allow the PS to offer a broader range of more accurate services to the client base.  For example, rather that delivering estimated elevation models based on a few RTK points, she can now deliver very dense point cloud derived models based on dense image matching.

Perhaps the most exciting new business opportunity is the rapid collection of accurate volumetric data.  Today this is done either by manned aerial mapping or by ground based techniques.  Ground based techniques are very problematic for many situations since accurate data collection of complex or tall stockpiles is very difficult.  Manned airborne methods work extremely well but are prohibitively expensive for high frequency monitoring (even quarterly monitoring is not practical except for the most valuable of stockpiles).  Enter the sUAS.  A flight of 20 minutes can provide the base data necessary for very detailed volumetric computations over a typical 1 square kilometer area.  In fact, the entire process, from mission planning to client deliverable can be performed in less that one day.

The sUAS is upon.  Enterprising folks will figure out very quickly how to produce professional products at a profit.

(Read the GeoConnexion article describing our experience of putting together an sUAS system.)