AU2015246588A1 - Method and system for detecting saturated or non-irrigated areas in leach heaps, in order to assist with the management and control of irrigation in leach heaps - Google Patents

Abstract

The invention relates to a method and system for detecting saturated areas or non-irrigated areas in leach heaps, in order to assist with the management and control of irrigation in leach heaps, including: a) positioning a highly stable and controllable unmanned aerial platform having an infrared thermal camera mounted thereon, at a predetermined height above one of the ends of the leach heap by means of a remote-control system, or by means of an autonomous positioning system; b) overflying said heap using flyovers at a predetermined height above said heap; c) acquiring/capturing thermal images of the heap, and sending said images wirelessly to a computer; d) thermographically reconstructing in a computer said thermal images captured, reconstructing the entire heap and generating a thermographic map of same; e) classifying the thermographic map, based on three classes associated with the irrigation conditions: saturated area, correctly irrigated area and dry area; f) determining the irrigation areas in accordance with the classification made, where black (0) is the saturated area, grey (127) is the correctly irrigated area and white (255) indicates the dry area; and optionally g) controlling the irrigation, whether manually or automatically, by taking the corresponding control action; and a system for implementing said method.

Description

1

METHOD AND SYSTEM OF DETECTING SATURATION ZONES AND NON-IRRIGATED ZONES IN LEACHING HEAPS, FOR THE PURPOSE OF ASSISTING IN THE MANAGEMENT AND CONTROL OF SPRINKLING ON LEACHING HEAPS 5 FIELD OF THE INVENTION

The present invention refers to a system and method for detecting saturation zones by means of an unmanned aerial platform equipped with an infrared thermal camera for the management and control of irrigation in leaching heaps.

10 PRIOR ART

The principal problems in leaching heaps are: • Formation of pooling zones on the surface of leaching heaps: These pooling zones do not allow the solution to be distributed uniformly over the width and length 15 of the heap, seriously compromising the productivity of the heap and the stability thereof. • Manual detection of the zones, through inspection by operators on the ground: These zones are monitored by operators who in most cases have to go up onto the 20 heaps to perform some type of service on the irrigation systems (by sprinklers or dripping), exposing themselves to an environment harmful to the health, and of significant danger to their physical safety. 25 · Leaching heaps can be large and extensive, such that they can reach 3,000 meters long by 1,000 meters wide and 10 meters high, with a slope angle of about 37°. 2

Detection and manual inspection in these zones are extremely challenging and complex due to the magnitude of distances, and the resulting difficulty of access on the heap due to the height (10 meters) of the slope . • Detection by a heap monitoring system with an elevated fixed camera is also complex, due to the magnitude of distances and dimensions. Moreover, problems of resolution and distortion appear due to the angle of the camera with respect to the surface to be monitored. • Because of the dimensions it is absolutely necessary to have a movable detection system, based not only on the distances but also on the results that can be obtained, because with a movable system the zones of interest can be approached at an optimal position and angle . • Long irrigation time in the pooling zone before its detection: This long time period has negative consequences due to a resulting decrease in the productivity of the heap. • Formation of saturated zones inside the heap: Detecting these interstitial saturation zones would guarantee suitable control of the geo-mechanical stability of the heap, avoiding possible collapses. 3 • Collapse of the heap due to said saturated zones: This is a catastrophic consequence due to late detection or non-detection of a saturated zone. • Slippage of slopes due to channelling of solution: This is a type of problem that generates an anomalous distribution of material in the heap, affecting the leaching process. • Loss of recovery due to low rate of leaching: If the solution does not filter properly through the heap, there is less recovery of copper due to a lower rate of leaching. • Loss of human life due to collapse of the heap: Those who are affected are primarily the operators of the heap, who go up onto it to carry out monitoring and control of the irrigation. As a result of collapse, they become trapped inside the heap. This is a catastrophic consequence that cannot continue to occur.

In the prior art there are various systems for monitoring or detecting heat sources in open areas; for example patent application CL 8-94 filed with the INAPI [National Industrial Property Institute] on 4 January 1994 by Izar Construcciones Navales, S.A., Spain, describes a system for monitoring and detecting heat sources in open areas, which comprises a system made up of observatories that include autonomous means of infrared and diurnal vision that are linked to a central control station, which processes the 4 images in real time, for the automatic detection of heat sources, especially fires inside the coverage zone. The system is applicable to the automatic detection of forest fires in areas covering various square kilometres. CL 8-94 uses thermal cameras to detect heat sources, specifically fires in an area of coverage. It does not mention or suggest a possible application to leaching heaps with the objective of examining and detecting, by means of thermographic analysis, the possible zones in which saturations can develop due to local impermeabilities. It also does not indicate the use of an infrared thermal camera mounted on an aerial platform to monitor temperature levels produced by the heat exchange between a leaching heap and the environment. W02004027099, Geobiotics LLC., describes a method for controlling the process, in leaching heaps, that comprises controlling the rate of irrigation of a heap as a function of the aeration rate of the heap, determining advection in at least one predetermined point in the heap, and determining the temperature in at least one specific point in the heap. Aeration of the heap is by natural or forced convection, and the rate is controlled as a function of the oxidation rate of material within the heap. The average rate of aeration and average rate of irrigation are maintained within the range of 0.125:1 to 5:1. Moreover, a method is described for introducing microorganisms in the heap, a method for increasing the temperature of the heap for leaching, a method for determining an optimal heap configuration for a process of bio-assisted heap leaching, 5 and a method for enriching the environment of microorganisms placed in a heap for bio-assisted heap leaching. W02004027099 performs irrigation control, using different 5 control variables from the variables of the present invention, i.e. rate of aeration of the heap, advection and at least one predetermined point and temperature at least one specific point in the heap. It does not teach or suggest the use of an infrared thermal camera for the 10 purpose of examining and detecting, by means of thermographic analysis, the ; possible zones in which saturations may develop due to local impermeabilities, monitoring the temperature levels, product of the heat exchange between the heap and the environment. 15 The patent application CL 1677-08 filed with the INAPI on 6 June 2008 by Mining Systems S.A., Chile, describes equipment and an associated method for the monitoring, maintenance and control of irrigation for leaching heaps, to correct problems of uniformity of fluid on leaching 20 heaps, to be installed in an irrigation network that includes main pipes that extend longitudinally at one side of the heaps, distribution pipes parallel to each other that extend through the heap from the main pipes at specific intervals, and emitter lines that are parallel and 25 at sufficiently close intervals, that are extended longitudinally from the distribution pipes to the drainpipes, where each emitter line has a plurality of outlets or sprinklers for the fluid to be supplied, a pressure sensor to determine the theoretical flow rate, an 6 irrigation control valve connected to each distribution pipe to establish different rates of irrigation, a turbidity sensor and at least one ON/OFF valve in each drainpipe to perform the cleaning of the network, a flow meter in each distribution pipe to determine the real rate, at least one device for monitoring the process variables at different levels (02, pH and temperature) , at least one fluid content sensor to measure a profile with which it is moistened. Each sensor has a means for the wireless transmission of the information to repeater antennas, and each valve has a means for being wirelessly actuated, wherein said means for each sensor and valve are disposed in tubular receptacles of high density polyethylene that rest on the surface of the heap. Moreover, the computerized control system receives the information transmitted by the repeater antennas, for the monitoring and control through the remote control of said valves.

In CL 1677-08, irrigation control is provided but the variables used for such control (02, pH and temperature in at least one specific point in the heap) are different from those of the present case. Furthermore, CL 1677-08 does not teach or suggest the use of an infrared thermal camera for the purpose of examining and detecting, by means of thermographic analysis, the possible zones in which saturations may develop due to local impermeabilities, monitoring the temperature levels, product of the heat exchange between the heap and the environment.

Patent application CL 1968-11 filed with the INAPI On 11 August 2011 by Applied Edge Technologies SpA, Chile, 7 describes a stationary control system for leaching and bioleaching heaps that includes communication, control and measurement of variables directly in the material of the heap, which is applied in mining and extraction processes. Patent application CL 698-12 filed with the INAPI on 21 March 2012 by Villagra Berrios Carlos Nelson, Chile, describes an autonomous, automatic and stationary system of wetting dynamic leaching heaps, which enables homogeneous irrigation in leaching heaps, composed of solar panels, current rectifier, battery kit, controller, solenoid, pressure reducing valve and on-off controls.

In CL 1968-11 and CL 698-12, control of the leaching heaps irrigation is accomplished, but stationary means are used on the heap. The use of an infrared thermal camera is not described or suggested for the purpose of examining and detecting, by means of thermographic analysis, the possible zones in which saturations may develop due to local impermeabilities, monitoring the temperature levels, product of the heat exchange between the heap and the environment.

Patent application CL 728-12 filed with the INAPI on 23 March 2012 by Aplik S.A., Chile, describes a system and method of monitoring and control of failures in irrigation on leaching heaps, which comprises: a thermal imaging system and a visible spectrum imaging system which captures images over zones of leaching heaps; an orientation system that selectively directs the lens of the thermal imaging and the visible spectrum imaging systems; a processing system that interacts with the thermal and visible spectrum 8 imaging systems, processing information, identifying, quantifying and classifying from the captured images surfaces according to moisture levels in dry zones, wet zones and saturated zones; and a user interface that displays the information processed by the processing system and allows the user to control variables of the thermal imaging and visible spectrum imaging systems, and of the orientation system, and thus enable the control of the process of irrigating leaching heaps (see Figure 1). Furthermore, CL 728-12 describes a method for quantitatively evaluating irrigation failures of at least one leaching heap, which comprises the following steps: a) having a thermal imaging system and a visible spectrum imaging system which observes a plurality of modules or variable areas of the leaching heaps for capturing images, through the following steps: capturing thermal images and images in the visible spectrum of the module; quantifying the percentage of surface of dry zones and irrigated zones from temperature distributions on the surface of the module; quantifying the percentage of surface of saturated zones from textures in the visible spectrum images; b) ordering the modules according to their percentage of surface for each level of moisture; c) selecting modules that are outside predetermined control limits; d) evaluating irrigation efficiency in each module and in the leaching heap; e) periodically displaying information about the irrigation status of the modules outside the control limits, which is shown on a user interface and generates an 9 irrigation status map of the heap; and f) applying control measures on the modules below the control limits. CL 728-12 describes an apparatus and process that uses an infrared thermal camera for the purpose of examining and detecting, by means of thermographic analysis, the possible zones in which saturations may develop due to local impermeabilities, monitoring the temperature levels, product of the heat exchange between the heap and the environment. However, CL 728-12 uses and suggests the use of an stationary infrared thermal camera, unlike the present invention which uses an infrared thermal camera mounted on an unmanned aerial platform to perform the thermographic analysis on the leaching heap.

Thus, CL 728-12 describes a process and apparatus that employs means that are different from those of the present invention, for example it uses a stationary infrared thermal camera. However, the present invention uses an infrared thermal camera mounted on an unmanned aerial platform, which allows a more uniform monitoring resolution in all of the areas, and thus makes it possible to detect precisely and with certainty the zones of interest, whether saturated or dry zones. By this information the control loop of the irrigation system can be efficiently closed, consequently optimizing the irrigation of the heap. US20060054214 describes a system for the intelligent irrigation of an area, which comprises at least one sensor for the control of particular environmental conditions, and at least one electrically operated valve that receives wireless information signals from the sensor and controls 10 an irrigation device based on the signals; and power control units repeatedly alternate the sensor and the valve between the states with and without motor in order to conserve energy. US2008129495 describes an automatic irrigation control system that comprises multiple nodes of sensors and multiple nodes of actuators, with each sensor node including a wireless transceiver, a processor and a sensor device. Each actuator node includes a wireless transceiver, a processor and an actuation circuit to actuate at least one irrigation valve.

In operation, a first sensor node communicates with a first node of the actuator through wireless communication, sending data from the sensors or the control commands to activate or deactivate the irrigation.

Moreover, the first sensor node can transmit messages to the first actuator node through other sensor or actuator nodes in the system in which the other sensor or actuator nodes act as repeaters for the retransmission of messages. US20060054214 and US2008129495 perform automatic control of irrigation for domestic or agricultural irrigation, and the variables used as control factors are those of the environment. Consequently these developments have characteristics and purposes that are different from those of the present invention, not defining the use of an infrared thermal camera for the purpose of examining and detecting, by means of thermographic analysis, the possible zones in which saturations may develop due to local impermeabilities, monitoring the temperature levels, 11 product of the heat exchange between the heap and the environment.

Furthermore, US20060054214 and US2008129495 have applications and technologies that are clearly different from those of the present invention.

Thus, in general none of the documents discussed above describe or show the use of an infrared thermal camera mounted on an unmanned aerial platform for thermal analysis of zones of a leaching heap.

The present invention refers to a system and method for detecting saturation zones by means of an unmanned aerial platform equipped with an infrared thermal camera for the management and control of sprinkling on leaching heaps. BRIEF DESCRIPTION OF THE INVENTION

The invention consists of a method for detecting pockets or excess moisture in leaching heaps. The method is based on a mechatronic system capable of generating aerial views by overflights of the leaching heaps, especially leaching heaps of large dimensions, where the solution of a fixed monitoring system is not viable and impossible to implement, or, in the best of circumstances, allows deficient results to be obtained with very low resolution; the objective is to examine and detect, by thermographic analysis, the possible zones in which saturations due to local impermeabilities could develop. Such a situation could trigger a possible liquefaction of the heap. Such a phenomenon must be considered, analysed, and obviously above all, avoided. With the objective of reducing the possibility of collapse and ensuring the geo-mechanical 12 stability in the heap, the irrigation system must be optimally controlled. For example, in a potentially saturated zone, the localized irrigation in that zone could be reduced or eliminated, until the saturation has disappeared.

Said mechatronic system consists of an unmanned aerial platform, highly stable and manoeuvrable, equipped with an infrared thermal camera. Said aerial platform is a battery-powered multi-rotor aerial vehicle in which MEMS sensors and a microcontroller are mounted. It can be operated by remote control through a radiofrequency system, or it can fly autonomously. Thus, the platform can be for example a glider, a motorized glider, a paraglider, dirigible, gyrocopter, airplane or something similar. The infrared thermal camera is used to monitor the temperature levels, produced in the heat exchange between the heap and the environment. This thermal information is very relevant, because it can provide an estimate of the saturation level in the different zones of the heap.

The images captured from the unmanned aerial platform are sent to a computer that processes the data, generating a map of the irrigation conditions of the heap. Consequently, irrigation zones are established: dry zone, properly irrigated zone and saturated zone. In turn, this information is sent to the irrigation system, which can be of the automated type (for example by means of a PLC), or by an operator who uses manual control.

Thus, the present invention is applicable in all heaps by means of which there are dynamic processes related to 13 leaching and/or bioleaching, whether the heaps are fixed and/or dynamic (on/off type).

An objective of the present invention is to improve the management of leaching heaps by means of aerial supervision of the heaps, through geo-referenced thermographic images which make it possible to distinguish dry zones, highly saturated zones as well as those that are properly irrigated.

An objective of the present invention is also to increase the rate of leaching, recovery and economic results in oxide plants.

Another objective of the invention is to reduce lost-time incidents and accidents at the heaps, completely eliminating fatalities during operations. Moreover, the invention assists in decision-making in the irrigation control system.

The present invention is related to control of permeability, and thus the stability of the heap, and intends to detect the zones where there are high levels of impermeability, and consequently pooling of solution. It also endeavours, by means of control action, to generate ideal irrigation conditions so that in those saturated zones excess moisture is not produced, thus always maintaining a uniformity of the level of moisture of the heap, avoiding slippage of embankments by channelling of solution and avoiding possible geo-mechanical collapses.

In this way, the present invention is related to the use of an unmanned aerial platform that carries out monitoring with infrared thermal camera by repeatedly overflying the 14 heap (see Figure 4), with the objective of taking control action and assisting in the decision-making in the irrigation of the heap, so that the irrigation is done efficiently and does not generate an undesired level of 5 moisture, and of course helping to eliminate the saturation that had been detected.

BRIEF DESCRIPTION OF THE FIGURES FIGURES 2A and 2B Illustrate the configuration of a comparative analysis for the fixed infrared thermal 10 camera system of the prior art. FIGURES 3A and 3B Illustrate the configuration of the comparative analysis for the fixed infrared thermal camera system of the prior art. FIGURE 4 Illustrates the arrangement of the mechatronic 15 system of the present invention. FIGURE 5 Illustrates a side view in perspective of the model of the mechatronic system of the present invention at the leaching heap. FIGURE 6 Illustrates an isometric view in perspective of 20 the model of the mechatronic system of the present invention at the leaching heap. FIGURE 7 Illustrates a top view in perspective of the model of the mechatronic system of the present invention at the leaching heap. 25 FIGURE 8 Illustrates a view of the mechatronic system of the present invention. FIGURE 9 Illustrates a bottom view of the mechatronic system. 15 FIGURE 10 Illustrates a flowchart of the method of the present invention. FIGURE 11 Illustrates an example of a thermal image for an embodiment of the present invention. The saturated zones are in dark blue, while the white zones correspond to zones of the heap that are not irrigated. FIGURE 12 Illustrates the histogram for each class associated with an embodiment of the present invention. FIGURE 13 Estimate of the Gaussian models given the distribution of data from the histograms. FIGURES 14A1-14D2 Illustrate some examples of segmentation for one embodiment of the present invention. 14A1, 14B1, 14C1, 14D1: the thermal images. 14A2, 14B2, 14C2, 14D2: the segmented images. DETAILED DESCRIPTION OF THE INVENTION.

As was mentioned in the previous section, the invention consists of a method for detecting pockets or excess moisture as well as dry zones in leaching heaps. The method is based on a mechatronic system, comprised of an unmanned aerial vehicle which has a thermal camera mounted on it, aimed towards the ground, capable of generating aerial views by overflights of the leaching heaps, especially leaching heaps of large dimensions, where the solution of a fixed monitoring system is not viable and impossible to implement, or, in the best of circumstances, allows deficient results to be obtained with very low resolution; the objective is to examine and detect, by thermographic 16 analysis, the possible zones in which saturations due to local impermeabilities could develop. Such a situation could trigger a possible liquefaction of the heap. Such a phenomenon must be considered, analysed, and obviously above all, avoided. With the objective of reducing the possibility of collapse and ensuring the geo-mechanical stability in the heap, the irrigation system must be optimally controlled. For example, in a potentially saturated zone, the localized irrigation in that zone could be reduced or eliminated, until the saturation has disappeared.

Said mechatronic system consists of an unmanned aerial platform, highly stable and manoeuvrable, equipped with a thermal camera. Said aerial platform is a battery-powered multi-rotor aerial vehicle in which MEMS sensors and a microcontroller are mounted. It can be operated by remote control through a radiofrequency system, or it can fly autonomously. The thermal camera is used to monitor the temperature levels, produced from the heat exchange between the heap and the environment. This thermal information is very relevant, because it can provide an estimate of the saturation level in the different zones of the heap.

The images acquired from the multirotor unmanned aerial vehicle are sent to a computer which processes said images, generating a map with the irrigation zones of the heap. Said zones provide information about the irrigation conditions of the heap. Consequently, irrigation zones are established: dry zone, properly irrigated zone and saturated zone. In turn, this information is sent to the 17 irrigation system, which can be of the automated type (for example by means of a PLC), or it can be manually controlled by an operator.

To monitor the levels of moisture in the heap, the present invention uses the thermographic information provided by an infrared thermal camera. Indeed, this type of information is correlated with the zones where saturations and/or dry zones are generated. The information related to the spatial location of such zones is sent, in turn, to the irrigation control system, which can be automated or manual.

The degree of impact of the present invention is high, as regards the associated benefits, among which the following can be mentioned: • Automated Monitoring System of the Heap. • Identification of Sectors with High Impermeability. • Intelligent Control of the Irrigation. • Geo-mechanical Stability of the Heap. • Uniformity of Flow. • Higher Concentration of Cu++. • Greater economic benefit. • Eliminates the use of manual operation of the heaps. • Reduction of lost-time incidents and accidents. • Reduction of infrastructure costs. • Eliminate fatalities due to collapse in the heap.

Thus, the method of the present invention can be implemented, preferably based on the following stages or steps : 18 a) Positioning unmanned aerial vehicle: The multirotor unmanned aerial vehicle, with thermal camera installed, is positioned at a specific altitude over one of the ends of the leaching heap by means of a remote-control system, or by means of an automated positioning system. b) Leaching heap overflight: The unmanned aerial platform makes overflights at a specific altitude over the leaching heap with the infrared thermal camera installed. c) Acquisition of thermal images: Thermal images are acquired of the heap, which are sent wirelessly to a computer . d) Thermographic reconstruction: With all of the captured thermal images, a thermographic reconstruction of the whole heap is performed in a computer, generating a thermographic map of the heap.

e) Classification of the thermographic map: A classification is performed of the thermographic map of the heap. Three classes are determined which are associated with three irrigation conditions. Said classes are: irrigation saturated zone, properly irrigated zone and dry zone . f) Determination of the Irrigation Zones: Three zones are determined according to the classification performed: Black (0): for saturated zones. Grey (127): for properly irrigated zones. White (255): for dry zones.

g) Irrigation Control: The respective control actions are taken, which may be performed manually or automatically. EXAMPLES

Comparative Example 19

According to the proposed mode of continuous monitoring of leaching heaps, the following comparative analysis seeks to demonstrate empirically that the method of monitoring carried out by infrared thermal camera incorporated in a hexacopter (the present invention) delivers much better thermographic information, from the point of view of resolution, then the method of monitoring with fixed infrared thermal camera (prior art, particularly CL 728-12) .

To demonstrate the advantages of the present invention compared to CL 728-12, a comparative study was performed by an example according to a condition introduced in said document, i.e. in CL 728-12. Said condition is represented according to the following parameters:

Height of Observation Tower: 40 meters and 60 meters Altitude of Hexacopter Flight: 5 meters Tower-Pile Distance: 15 meters Dimensions of the Leaching Heap:

Height of Heap: 7.5 meters Heap Length: 600 meters Heap Width: 250 meters Slope Width: 11.25 meters

The infrared thermal camera used for the analysis is a FLIR Tau 320 camera, 9mm-fl.25, with the following characteristics :

Resolution: 640 x 480 Vertical FOV: 38.4°

Horizontal FOV: 48°

Spectral band: 7.5-13.5 pm 20

Temperature range: -40 to +80°C

The fixed infrared thermal camera installed at a height of 40 m, is actuated and can therefore be turned with respect to the vertical axis (tilt angle) and horizontal axis (pan angle). The maximum and minimum angles necessary for completely observing the heap with respect to the vertical axis correspond to 58.13° and 65.97°, respectively.

However, to completely observe the heap with respect to the horizontal axis, said angles correspond to -84.8° and 84.8° .

Therefore, a measurement was made of the real area comprising one pixel within the space of the image. The pixels selected were those of the ends, middle ends and centre. The purpose was to compare, from the point of view of resolution, the results delivered by a fixed camera versus a mobile camera. Evidently, depending on the vertical and horizontal angular configurations (tilt and pan), different resolutions will be obtained with fixed camera. The configurations chosen, therefore, are those that allow the lowest number of scans in order to cover the whole surface of the heap.

Table 1: Data for configuration 1 of the prior art of fixed infrared thermal camera, see Figures 2A and 2B Horizontal angle (Tilt angle) = 58.13°, Vertical angle (Pan angle) = -62.68or

Pixel Area, m2 i j 0 0 0.003823259 21 319 0 0.003823259 639 0 0.003823259 639 239 0.014433413 639 479 0.168763785 319 479 0.168763785 0 479 0.168763785 0 239 0.014433413 319 239 0.014433413 Horizontal angle (Tilt angle) = 58.13°, Vertical angle (Pan angle) = -18.42or Pixel Area, m2 i j 0 0 0.003823259 319 0 0.003823259 639 0 0.003823259 639 239 0.014433413 639 479 0.168763785 319 479 0.168763785 0 479 0.168763785 0 239 0.014433413 319 239 0.014433413 Horizontal angle (Tilt angle) = 58.13°, Vertical angle (Pan angle) = -18.42or Pixel Area, m2 i j 0 0 0.003823259 319 0 0.003823259 639 0 0.003823259 22 639 239 0.014433413 639 479 0.168763785 319 479 0.168763785 0 479 0.168763785 0 239 0.014433413 319 239 0.014433413 Horizontal angle (Tilt angle) = 58.13°, Vertical angle (Pan angle) = -62.68or Pixel Area, i j 0 0 0.003823259 319 0 0.003823259 639 0 0.003823259 639 239 0.014433413 639 479 0.168763785 319 479 0.168763785 0 479 0.168763785 0 239 0.014433413 319 239 0.014433413 (Tilt angle) = -62.68°.

Table 2: Data for configuration 2 of fixed infrared thermal camera of the prior art, Figures 3A and 3B 5 Horizontal angle (tilt angle) = 65.97°, Horizontal angle Pixel Area, m2 i j 0 0 0.005603887 319 0 0.005603887 639 0 0.005603887 23 639 239 0.031415218 639 479 2.938017999 319 479 2.938017999 0 479 2.938017999 0 239 0.031415218 319 239 0.031415218 Horizontal angle (tilt angle) = 65.97°, Horizontal angle (tilt angle) = -18.42° . Pixel Area, i j 0 0 0.005603887 319 0 0.005603887 639 0 0.005603887 639 239 0.031415218 639 479 2.938017999 319 479 2.938017999 0 479 2.938017999 0 239 0.031415218 319 239 0.031415218 Horizontal angle (tilt angle) = 65.97°, Horizontal angle (tilt angle) = 18.42°. Pixel Area, m2 i j 0 0 0.005603887 319 0 0.005603887 639 0 0.005603887 639 239 0.031415218 639 479 2.938017999 24 319 479 2.938017999 0 479 2.938017999 0 239 0.031415218 319 239 0.031415218

Horizontal angle (tilt angle) = 65.97°, Horizontal angle (tilt angle) = 62.68°.

Pixel Area, i j 0 0 0.005603887 319 0 0.005603887 639 0 0.005603887 639 239 0.031415218 639 479 2.938017999 319 479 2.938017999 0 479 2.938017999 0 239 0.031415218 319 239 0.031415218

Now, if the hexacopter with infrared thermal camera overflies the heap at different heights above the surface 5 and orthogonal thereto, the following values are obtained: Height: 5 meters

Horizontal angle (tilt angle) = 0°, Horizontal angle (tilt angle) = 0 °.

Pixel Area, m2 i j 0 0 5.047 04E-05 319 0 5.047 04E-05 639 0 5.047 04E-05 25 639 239 5.047 04E-05 639 479 5.047 04E-05 319 479 5.047 04E-05 0 479 5.047 04E-05 0 239 5.047 04E-05 319 239 5.047 04E-05

Height: 10 meters

Horizontal angle (tilt angle) = 0°, Horizontal angle (tilt angle) = 0°.

Pixel Area, i j 0 0 0.000201882 319 0 0.000201882 639 0 0.000201882 639 239 0.000201882 639 479 0.000201882 319 479 0.000201882 0 479 0.000201882 0 239 0.000201882 319 239 0.000201882

Height: 15 meters 5 Horizontal angle (tilt angle) = 0°, Horizontal angle (tilt angle) = 0°.

Pixel Area, m2 i j 0 0 0.000454233 319 0 0.000454233 639 0 0.000454233 26 639 239 0.000454233 639 479 0.000454233 319 479 0.000454233 0 479 0.000454233 0 239 0.000454233 319 239 0.000454233

Height: 20 meters

Horizontal angle (tilt angle) = 0°, Horizontal angle (tilt angle) = 0°.

Pixel Area, i j 0 0 0.000807526 319 0 0.000807526 639 0 0.000807526 639 239 0.000807526 639 479 0.000807526 319 479 0.000807526 0 479 0.000807526 0 239 0.000807526 319 239 0.000807526

Comparing the areas per pixel, it is determined that the 5 farther away the camera shot is from the tower, the area represented by one pixel increases to 2.938 m2 in the most unfavourable configuration. This low-resolution has a negative impact on the monitoring of the zones of interest (saturated zones and dry zones), and consequently on the 10 decision-making for the management and control of the irrigation. 27

On the contrary, with the thermal camera mounted on the hexacopter the area represented by one pixel is always the same (for example 5.04704E-05 2 at 5 meters); nevertheless, this increases as the overflight altitude of the hexacopter increases. It should also be noted that the resolution is always the same, and what is more important, it is always high relative to the fixed camera method. Consequently, it makes it possible to detect with precision and certainty the zones of interest, whether saturated or dry. By this information the control loop of the irrigation system can be efficiently closed, consequently optimizing the irrigation of the heap.

For the complete analysis of the heap with a fixed camera installed on a tower, only 8 scans are needed. However, with a mobile camera installed on a hexacopter 8,474 scans are needed at an altitude of 5 meters, 2,119 scans at an altitude of 10 m, 942 scans at an altitude of 15 m and 530 scans at an altitude of 20 m. Nevertheless, this is not a problem because the dynamic of the heap is slow, so high frequency monitoring is not necessary. Moreover, if the dimensions of the heap were different, i.e. larger, especially in the length and width, the need to monitor with hexacopter is even more obvious, given the low resolution delivered by the system of monitoring with fixed thermal camera mounted on a tower.

Example: Irrigation control in leaching heaps with hexacopter and thermal camera

The principal objective of the present mechatronic system, which integrates the use of a hexacopter with a thermal 28 camera, seeks control of the irrigation of leaching heaps with the object of avoiding saturation zones that can compromise, in addition to the leaching process itself, the geo-mechanical stability of the heap. In order to ensure early detection of the saturation zones the heap must be monitored, especially while irrigation is being carried out. However, a purpose of this system is also to recognize the zones that are not correctly irrigated, always with the objective of improving the recovery process. This monitoring action in particular has been achieved with a thermal camera installed on a hexacopter (see Figure 4).

The idea is to detect the saturated zones as well as the non-irrigated zones. This detection can be achieved by means of thermographic analysis, which can be accomplished in turn by means of a process of acquisition and processing of thermal images. Consequently, as such zones are detected, better actions can be taken to control the irrigation. In such a case, in those zones where there is an excess of solution, the respective valves must be kept closed.

The dimensions of the leaching heap under analysis are: Length: 48.4 meters x Width: 24.4 meters x Height: 2.5 meters .

The distance between two irrigation belts is 3 meters.

The thermal images were acquired with a FLIR TAU 320 infrared thermal camera, 9 mm-fl.25, with a sensitivity of 7.5 to 13.5 pm, and a resolution of 324 x 256 pixels.

The hexacopter used has the following characteristics: 29 • The size of the propellers is 26 cm, while the distance between two motors is 60 cm. • It includes an ArduPilot Mega 2.0 flight controller, which enables flights to be made by remote control as well as autonomously. • It is provided with an ATMEGA2560 microcontroller, a Honeywell model HMC5883L-TR digital compass, a Mediatek MT3329 on-board GPS, an Invensense MPU-6000 accelerometer/gyroscope with 6 degrees of freedom, and a Measurement Specialties model MS5611-01BA03 barometer. • It uses six Turnigy model L2215J-900 brushless motors controlled by a Turnigy model Basic 25A speed controller. • The total weight of the hexacopter is about 1 kg, and its load capacity is about 800 g. • The batteries used are lithium Polymer with a capacity of 5,000 mAh and a weight of 409 g.

To resolve the objective problem, three classes of zones in the heap were defined: saturated zone, properly irrigated zone and dry zone.

Considering all of the images taken at an altitude of 5 m (see Figure 4), they are divided into two sets of images. The first set of images is used for training the classifier, while the second set of data is used for its evaluation. The value of each pixel is used as a datum. Three histograms are calculated with these data (see Figure 12). Thus, three Gaussian models are estimated, given the distribution of data in the histograms (see Figure 13). Naive Bayes is a sufficiently reliable classifier based on 30 the maximum a posteriori (MAP) principle / for this reason, said classifier is used to determine the class of each pixel (Rish, I. (2001) 'An empirical study of the Naive Bayes classifier' , IJCAI Workshop on Empirical Methods in Artificial Intelligence, pp. 41-46).

Given a problem with K classes of a priori probabilitiesPiCj), „vtP(Cs) (Zhang, H. (2004) 'The Optimality of Naive Bayes', Proceedings of the Seventeenth International Florida Artificial Intelligence Research Society Conference (FLAIRS 2004), pp. 562-567), the class c can be assigned to an unknown example of characteristics X = such that: c = i

V \L= c

By means of which it is chosen as the class with the greatest a posteriori probability given the observation of the data (Mardia, K. V. and Kanji, G. K. (1994) Statistics and Images: 2.

Advances in Applied Statistics, Carfax Publishing Co. Ltd., Abingdon, Oxfordshire). This a posteriori probability can be formulated, using the Bayes theorem, as follows: __ __ ^ P(C = c)P(xlf...,Xj* I € = c) i)

Because the denominator is the same for all classes, it can be discarded when the comparison is made. At this point the conditional probabilities should be calculated of the classes of the characteristics given a class. This could be relatively difficult, considering the dependencies between characteristics. The Naive Bayes method assumes that the 31 classes are independent, for example, xa,..,{xs. This simplifies the expression in the numerator: P(C = c)P{xl I C = c)*P(x2 | C = c) * ...# P(xN IE C = c) and then selecting the class c that maximizes this value over all other classesc = 1, K. Clearly, this method can be applied to more than two classes. In this case, we have three independent classes. The principal assumption is that each class c has the same probability, so ?(€ = l) = P(C = 2) = P(€ = 3) = ^. Again, the denominator is always the same for all classes, so it can be discarded when comparing. Finally, for each pixel the class given is c = argmaxcP{ xa, I C = e).

The thermal images were classified according to the analysis explained previously in the 3 different classes. Each class was associated with the colour on the greyscale, see Figure 14 (A2-D2), where: • Black (0): for saturated zones. • Grey (127) : for properly irrigated zones. • White (255): for dry zones.

It can clearly be seen that the classification of the thermal images has given excellent results, providing solid information about the zones of interest. Through the processing of images, it is possible to detect specifically where the saturated and/or dry zones are located, as well as the zones that are properly irrigated. Moreover, because the irrigation systems (by dripping or by sprinkling) are determined by the irrigation lines, it is simple to recognize which irrigation line in particular needs to be 32 controlled. Consequently, by means of the analysis and processing of images, this type of information can be provided to the controller, in order to improve the irrigation system automatically. Thus, if a saturated zone is thermographically detected, this information is provided to the controller in order to make the corrective action; for example, the respective valves to those irrigation lines should be closed until the saturation is dissipated. Considering the opposite case in which there are dry zones in the heap for example, the irrigation control system should send an increased flow and/or open the valves again. Because an excess of moisture can seriously affect the stability of the heap, increasing the risk of collapse due to liquefaction, said monitoring system helps to maintain the stability of the heap. This results in increased safety in the management of the leaching process, eliminating the need to have a human operator make visual inspections in the vicinity of the heap, where a collapse due to liquefaction could seriously jeopardize the life of the operator .

Claims (4)

1. Method of detecting saturation or non-irrigated zones in leaching heaps, for the purpose of assisting in the management and control of irrigation in leaching heaps which comprises: a) positioning a highly stable and manoeuvrable unmanned aerial platform, with thermal camera installed, at a specific altitude over one of the ends of the leaching heap by means of a remote control system, or by means of an automated positioning system; b) leaching heap overflight wherein the unmanned aerial platform makes overflights at a specific altitude with the infrared thermal camera installed; c) acquisition of thermal images, wherein thermal images of the heap are acquired and sent wirelessly to a computer; d) thermographic reconstruction of the captured images is performed in a computer, and the thermographic reconstruction of the whole heap is performed, generating a thermographic map thereof; e) classification of the thermographic map, based on 3 classes, which are associated with 3 irrigation conditions: saturated zone, properly irrigated zone and dry zone; f) Determination of the irrigation zones, 3 zones are determined in accordance with the classification performed, where black (0) indicates saturated zones, grey (127) indicates properly irrigated zones and white (255) indicates dry zones; and optionally g) irrigation control, wherein the corresponding control action is taken, which may be performed manually or automatically.

2. Mechatronic system for the detection of saturation zones or non-irrigated zones in leaching heaps for the purpose of assisting in the irrigation management and control of leaching heaps that comprises a highly stable and manoeuvrable unmanned aerial platform, equipped with an infrared thermal camera, wherein said aerial platform is a multi-rotor aerial vehicle, powered by batteries with MEMS sensors and a microcontroller mounted therein, and said platform can be operated by remote control by means of radiofrequency system, or can fly autonomously, and wherein said infrared thermal camera is used to monitor the temperature levels, product of the heat exchange between the heap and the environment; and wireless means for sending the thermal images captured by the infrared thermal camera to a computer which performs the thermographic reconstruction of the captured thermal images and a classification and determination of 3 classes of zones: irrigated saturated zone, properly irrigated zone and dry zone .

3. Mechatronic system of claim 1, wherein the unmanned aerial vehicle is selected from the group consisting of a glider, a motorized glider, a paraglider, a dirigible, a gyrocopter or an airplane.

4. Mechatronic system of claim 1, wherein the multirotor unmanned aerial vehicle is an X-copter.