15arspc Submission 194

8/8/2019 15arspc Submission 194

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USING AIRBORNE THERMAL INFRARED SENSORS TO SURVEY FERAL

CAMELS

A. Mabarrack1, M. Feldmuller1, P. Dare2, J. Pitt1 and P. Gee11Rural Solutions SA

Level 8, 101 Grenfell Street, Adelaide, South Australia, 5000Phone number 08 8842 6261

[email protected]

2Spatial Scientific Technologies Pty Ltd.

PO Box 520, Blackwood, South Australia, 5051Phone number 08 8376 0772

[email protected]

Abstract

Current broad scale aerial survey techniques for estimating the densities ofanimal species such as camels, horses, and donkeys are labour intensive,costly and time consuming. It is generally recognised that the strip-transectaerial method is subject to several sources of error including observer skill andvisibility bias. It can also be compromised by animal behaviours such asherding and dispersal which are determined by climatic and other factors.

This paper presents an analysis of the use of a FLIR A320 Thermal InfraRed(TIR) camera attached to aircraft to survey feral herbivore distribution and

density. Although this application of TIR has been trialled previously (Locke etal, 2006 & Greirson & Gammon, 2002), recent advances in thermal imaging,data processing, and GPS and computer software technologies now offer anopportunity to improve methodologies and outputs.

The ability to detect and differentiate the thermal signature of camels frombackground terrain and vegetation was investigated under both winter andsummer conditions. Operational parameters were identified in which camelscould be thermally distinguished from their surroundings under daylightconditions. Thermal imagery was found to be affected by altitude, direction,camera angle, time of day (sun elevation), and season. Adequate thermal datacapture was found to occur with TIR cameras mounted obliquely to aircraft and

thermal data of camels captured between sunrise and midmornings and in lateafternoon to sunset.

The physiological, morphological and behavioural adaptations of camels whichmake them well suited to desert survival and extremes in temperatures arediscussed in terms of their likely impact on the results obtained and theoperational applicability of an aerial TIR survey method for the survey of feralcamel density and distribution.

While camels have been the focus of this research, findings are potentiallytransferable to the thermal survey of other target species such as kangaroos,horses, donkeys, goats, deer, pigs and foxes.


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Introduction

Considerable intelligence regarding the number, distribution and impacts ofvertebrate pest species such as feral camels is fundamental to inform andprioritise control activities and to ensure positive investment outcomes.

Aerial surveys can be used to gain such intelligence in remote areas quicklyand efficiently as compared with on-ground approaches. Consequently, visualaerial surveys have been used for decades at a range of scales for populationsurvey and for targeting control operations. The widespread distribution, highmobility and cryptic nature of feral camels, however, have highlighted the needfor improved aerial survey methods to meet landscape scale pest managementmonitoring and operational requirements.

The strip-transect aerial survey method requires three skilled observers flown ina light aircraft at an average altitude of 250ft above ground level at 100kts(185km/hr) over predetermined transects across the survey area. In winter

months survey work is generally carried out between 8:00am and 11:30am andthen between 12:30pm and 5:00pm. Aerial surveys are generally not conductedin the summer months due to adverse flying conditions (Lethbridge and Pitt,2009).

There are a number of compromising issues with current broad scale visualaerial survey techniques: they are labour intensive, costly and time consuming.They can only cover a small (4-6%) proportion of the landscape due to costsand time constraints and population estimates may be prone to underestimationas observers do not see all animals. Adverse flying conditions (such as airdisturbance resulting from the thermals present during hot summer weather, the

time when feral camels often congregate) can also inhibit these low-level visualaerial surveys out of concern for the safety and well being of the pilot andobservers. The lack of experienced observers and the time required forobservers to recover from the demanding task can impede the conduct of visualaerial survey. Additionally the time required to process and analyse visualsurvey data can delay on-ground actions, and in the elapsed time camels mayhave moved in or out of the survey area, congregated or dispersed.

Thermal Infrared detection relies on an appreciable difference between TIRradiations emitted by the target object and surrounding features. The TIRradiation measured for an object is a combination of the emission obtained

from the objects surface, reflected emissions from ambient sources(surroundings) and the emissions from the atmosphere (Jenson, 2007).

The TIR radiation of animals can be affected by a range of factors:morphological features and adaptations (growth or shedding of winter coats),physiological mechanisms and adaptations (e.g. camels allowing bodytemperature to rise as a water conservation mechanisms when heat and waterstressed), behaviours (e.g. temporary torpor or hibernation to reduce metabolicheat production, shading, huddling, or orientation of the body laterally or parallelto the sun to increase or decrease solar heat absorption), elevation, directionand intensity of sunlight, ambient air temperature, and moisture content. Thesefactors are important considerations for any future adaptations of this method to


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other species as not all species have the same morphology and behaviouralcharacteristics.

The potential application of Thermal InfraRed (TIR) sensors for airborne TIRsurvey has previously been trialled with mixed results (Locke et al, 2006 &Greirson & Gammon, 2002). However, recent advances in thermal imaging,thermal data processing, GPS and computer software technologies now offeran opportunity to improve methodologies and outputs. Airborne TIR surveymethod has the potential to provide an adjunct or alternative method to visualaerial survey methods that is more rapid, automated, cost effective, and saferthan current visual aerial survey methods.

An important component for the operational application of airborne TIR surveyis the development of software to automate data processing. Automated, ratherthan manual techniques for data interpretation are necessary and desirable asthey are more time and cost efficient, easier to scale, and often more reliable.

Desirable automated processing steps include geo-referencing of thermalimagery and automated identification of selected species to establish countsagainst geo-reference points.

Feral camels were the target species for the research undertaken and reportedin this paper. There are an estimated 1-1.2 million feral camels (DKCRC)currently ranging across 3.3 million square kilometres of remote, arid Australia.They utilise a wide variety of land systems, from dense mulga woodland toopen savannah grassland and the vast longitudinal sand dune systems of thecentral deserts. Feral camels threaten natural and cultural assets andmanmade infrastructure. They are a significant threat to natural surface waters

and refugia and their dependent biota (through water depletion andcontamination), particularly in drought. Feral camels pose a threat to severalidentified tree and shrub species, and if numbers are not brought under control,local and regional scale extinctions of flora and fauna species can beanticipated.

Camels are clearly well adapted to desert environments. They have manymorphological, physiological and behavioural adaptations which allow them tosurvive extremes in temperature. They have a distinctive shape and areAustralias tallest land animal. Their large body means they can absorb andtolerate a large amount of heat (Manefield and Tinson, 1997).

Figure 1: Image taken of camels from the air over Todmorden Station


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Fat concentration in the hump serves to effectively shield vital organs from ahot summer sun and allows for easier heat loss from the rest of theircomparatively fat free body in summer. Their narrow profile from above limitsthe amount of body exposed to the midday sun (Figure 1) and their long skinny

legs help to distance them from heat radiating off hot desert surfaces. Toughcalloused pads on the feet, knees and chest pedestal (on which they rest whencouched) limit the amount of heat gained or lost by the body.

The camel grows a thick woolly coat for the cooler months of the year, whichhelps to insulate the body from cold ambient temperatures. The woolly coatgrows longest on the hump (10cm in winter) (Manefield and Tinson 1997) butalso extends along the length of the dorsal surface and well down the lateralsurfaces, effectively blanketing the camel when it is in the sitting position.Figure 2 (left) shows the woolly coat of a camel during the winter months. Thewoolly coat is usually shed at the start of warm weather (Figure 2 right) leaving

the camel quite bare skinned by early summer. The thick woolly coat does notreappear until late autumn.

Figure 2: Woolly coat of a camel during the winter months (left) the camel has moultedin early summer (right).

In addition to morphological adaptations the camel has physiologicaladaptations to enable it to conserve water and energy when required. Insummer when temperatures in the desert can reach into the high 50C range(Bonython, 1989) the camel is able to allow its core body temperature to risesignificantly during the day. During the night when the ambient temperature

reduces the camels core temperature cools again. The ability to allow the corebody temperature to rise during the day and fall during the night has the effectof minimising water loss through sweating. When dehydrated this coretemperature differential can be as much as 6C (with core temperature rising upto ~42

oC), but is typically only about 2C for a hydrated camel. The precise

circumstances under which this occurs are not understood (Manefield andTinson, 1997). Allowing the core temperature to rise also reduces thetemperature gradient between the camel and its environment thereby reducingfurther heating of the animal. Mechanisms to conserve or generate heat are notactivated until the animal reaches its lowest tolerable core temperature (~35-36C).


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The camel also employs a range of behaviours to maintain core bodytemperature. On cold winter nights the camel seats itself with its posteriorpointed into any breeze and, if possible, also tucked into a sheltering leafyshrub such as Acacia ligulata. In the early morning, at first light, it will bask in

direct sunrays (Figure 3 (left)) as soon as possible to warm up (Willmeret al.2005).

Measurements of the camels body temperature under different conditions havefound it to be affected by ambient temperature, water deprivation, dailyvariation and season. As a guide the winter core temperature of an adult camelis about 36-37C in the morning and about 38C in the afternoon and 36.5-38C in the summer morning and 39.5C in the summer afternoon. Additionally,the temperature of young camels is 0.5-1.0C higher than that of adults. Duringthe cold winter months the healthy camels body temperature will not fall below35-36C (Manefield and Tinson 1997; Higgins 1986). The male camel in rut has

also been found to have elevated core temperatures (Grigg et al. 2009).During the day however, camels will shelter from a hot sun (ambient approx.35C) will seek out a shady tree if it is available (Figure 3 (right)).

Figure 3: Camels basking in the direct sun at first light (left) and seeking out shadewhen hot (right)

This report describes investigations into the potential of TIR to differentiate

camels from their surroundings and to develop aerial TIR data capturemethodology and software to further the application and operational use of TIRfor aerial survey. Results obtained at each stage of the investigation informedsubsequent steps and method development. Although camels are the focushere the outcomes of this work potentially apply to other large warm bloodedspecies.

Methods

A series of preliminary trials (Figure 4) were undertaken in March & May 2009using the A320 camera from ground level and also from the air with the camera

mounted to a fixed wing aircraft. The ground trials involved capturing data of


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camel temperatures using the A320 camera and a laser range finder fordistance data. The aerial flight trials were conducted at a range of altitudesover selected properties/locations known to contain camels. This researchaimed to determine optimum flying height and camera angle for further data

collection and analysis. Data was captured during daylight hours and at night.A trial area was subsequently selected that was more representative of camelhabitat and in June 2009 (winter) a series of flights were undertaken. Daytimeflights were conducted over 8 camels located near William Creek (Figure 4),within the Irrapatanna Sandhills located within the Wattiwarrigana landsystem(Department for Primary Industries and Resources SA, 1996). The dominantshrub species isAcacia ligulata and the dunes have a 20% cover ofZygochloaparadoxa (sandhill canegrass). Sparse individual Acacia aneura (Mulga) werealso present.

Flights over these camels were conducted at various times between sunrise

and sunset between 16th and 18th June 2009 (winter). Altitudes selected rangedfrom 250-1500ft. TIR data was captured using the A320 camera mountedobliquely on a Piper Comanche light aircraft.

Flights were also conducted in late February of 2010 (late summer). In thesetrials camels were paddocked at Beltana Station (Figure 4) on Saltia landsystem pastures. The Saltia landsystem is comprised of alluvial foot slopes andplains of stony red soils with bladder saltbush, low bluebush and scatteredgroves of black oak and prickly wattle (Department for Primary Industries andResources SA, 1996).


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Figure 4: Location of Study areas

The A320 thermal imaging and Sony Cybershot digital visual cameras weremounted in tandem obliquely to a Bell Jet Ranger helicopter. Flights wereconducted at 250ft over camels at regular intervals throughout the day betweensunrise and sunset to capture both visual digital and thermal digital imagery.Imagery was captured flying north, south, east and west over the camels.

During the February 2010 (summer) trials GPS tracklogs were captured for

each flight series. These tracklogs were then downloaded and time stampedwith the thermal imagery sequence for use within software development.Ambient air temperatures were obtained from Bureau of Meteorology (BOM)websites from the nearest weather station.

The thermal imagery captured during both winter and summer daytime flightswas analysed using the FLIR Researcher 2.9 software to determine datacapture parameters for maximising the thermal difference between camels andbackground vegetation and terrain. Analysis was done with particular referenceto season, altitude, and angle of sun in relation to image capture and time ofday. Using the knowledge gained from the data analysis custom software was

developed to automate the image interpretation process.


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Results

The preliminary flights conducted in March and May 2009 failed to adequatelydetect camels during night time flights with the camera mounted vertically.These flights also indicated surveying above 1,000ft produced insufficient data

due to image resolution.

Thermal imagery of camels taken from ~5m off the ground using the A320mounted at an oblique angle at sunset demonstrated that the heat signature ofthe camels was clearly visible from this ground based view (Figure 5). Thethermal radiation emitted varied across different portions of the camels bodywith a larger thermal signature on the lower abdomen area and legs. In additionit was evident that the lateral view of the camel presents a much larger surfacearea than the dorsal surface of the camel.

Figure 5: Comparison of digital visual image (left) with A320 thermal image (right)

taken of camels at a distance of 250m prior to sunset. Both images were taken withinseconds of each other from ~5m above ground level on a slight oblique angle.

Comparative thermal and visual data are shown in Figure 5. Camels wereclearly visible thermally from ~250 metres up to ~600 metres away. The thermalradiation from the camel is clearly distinguishable as they are ~4

oC hotter than

background thermal sources just prior to sunset. Camels in the thermal imagewere more easily identified under these conditions than in the visual image.

For the aerial flights the quality of daytime TIR images improved as altitudereduced (Figure 6). Also, at the lower altitude, the shape of the camel was more

readily identifiable. As found previously, less TIR radiation is seen to be emittedfrom across the hump region of some camels with greater TIR emission alongthe flanks. In Figure 6 (right) the person shepherding the camels can also beseen (see the small heat signature above and the left of the top camel).


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Figure 6: A320 thermal images of camels in Sandhill country near William Creek.Camera mounted obliquely. Late afternoon flight conducted at 500ft (left) and at 300ft

(right). Thermal image taken of sun illuminated side of the camels.

During the summer trials the results highlight (Figure 7) that camels are clearlythe hottest elements in the image by ~3

oC for around a 3 hour period from

sunrise to midmorning (Figure 8). By mid afternoon (Figure 7) they become thecoolest elements in the image by ~1.0

oC. It is not until late afternoon/early

evening that they again become the hottest elements in the image by ~3oC. In

Figure 7 it can be seen that the comparison of thermal data at sunrise and justprior to sunset with the visual data that the camels in the thermal image aremore easily discernible than in the visual images.

Sunrise, flying south. 7 sitting camels thermally visible (left). 4 of the samecamels visually visible (right)

Mid Afternoon, flying east. 6 sitting camels thermally (left) and visually (right)

visible


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Early evening (sunset), flying south. 2 standing camels thermally (left) andvisually (right) visible

Figure 7: Sample thermal images taken with A320 camera (left) and comparable digitalvisual images taken at the same time with Sony cybershot TX1 (right). Images taken at

sunrise, midafternoon and at sunset of camels held in saltia landsystem at Beltana

Station. Cameras mounted obliquely on the lefthand side of the helicopter flown at250ft.

When comparing the averages for both summer and winter temperaturereadings the results obtained indicated that there were two main time periodsfor optimum data collection. These were between sunrise and midmorning andfrom mid afternoon to sunset, although the afternoon period of opportunity wasshorter (Figure 8). Figure 8 also indicates a greater temperature difference wasobtained between camels and background during winter.

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Figure 8: Comparison of temperatures taken from thermal images captured by A320camera of camels at 250ft at various times of the day during winter and summer.

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Temperature readings for camels, vegetation and background during each timeseries for all flight directions (except 10am south and east flights) are given inFigure 9. The results indicated that sun angle had an influence, with greatertemperatures being recorded when the sun was directly heating the camels

sides. This occurred at midmorning with camels appearing ~3o

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Figure 9: Summer directional comparison of temperatures for camels, vegetation andbackground, indicating early morning and late afternoon camera and sun angles

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Figure 10: Average temperature difference between camel & vegetation temperaturesmeasured from thermal images acquired in the winter and summer trials

When comparing average temperature differences between camel andvegetation throughout the day, (Figure 10) it was clear that for both winter andsummer there were two separate time periods when the camels TIR signaturewas hotter than the surrounding vegetation. The results also showed there wasa period in the middle of the day when the camels became cooler than thevegetation and it was shown that a greater thermal difference was obtained inwinter.

Maximum TIR differentials of 7oC were observed in winter about an hour after

sunrise at which time camels were observed to be browsing and basking in themorning sunlight and again about an hour before sunset. Maximum TIRdifferential between camels and surrounding vegetation were only ~3

oC in

summer. Again these were observed in the mornings and late afternoon. Duringthe middle of the day when camels were cooler than their surrounds this

differential reduced to ~1-1.5oC in winter, which was about the same asobserved in summer (i.e. ~1-1.5

oC).

Initial trials using the custom-developed software with the summer TIR datashowed that it is possible to successfully detect, count and extract absolutecamel counts in a GIS-ready format (Figure 11).


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Figure 11: Example of data output using the Camel Finder Software. The red shadedobjects are those features identified by the software as camel-like objects.

Discussion

In this series of trials the successful application of TIR imagery for camelsurveys was found to be dependent on a range of morphological, physiologicaland behavioural characteristics of the target animal as well as the thermalproperties of the surrounding environment. Collectively the results indicated that

airborne thermal imaging can be applied for the identification, counting anddistribution mapping of camels and potentially be applied to other warmblooded species. This series of trials added considerable understanding tounknown aspects regarding camera resolution, camera angle, altitude, time ofday and data analysis requirements.

Initial assumptions regarding the need to conduct surveys during winter, at nightand with a vertical camera position were found to be incorrect. Data collectedunder these initial trial conditions was inconclusive. Further trials proved thatwhen the FLIR camera was mounted obliquely the TIR radiation emitted fromthe larger, less insulated lateral surfaces of camels enabled a successful TIRdifference to be obtained. Camel and background thermal emissions were

readily differentiated during daytime trials conducted during winter and summerusing the oblique camera angle. This was an important finding as it removedthe risks associated with night time aerial surveys.

From the images in Figure 7 and the graph in Figures 8 & 10 it can be seen thatthe camels were hotter than surrounding vegetation in both the early morningsand late afternoons during summer and winter trials, with camels being coolerthan their surrounds during the middle of the day.

Sample stills of visual video imagery taken at the time of thermal video imagerycapture are presented side by side in Figure 7 for comparison. From these itcan be seen that there are times when camels which are visually difficult to seedue to their colouring can be quite distinct thermally.


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It was also found that differentiating camels from the background using thermalradiation could not be achieved at all times of the day. However, windows ofopportunity were found to exist for camel surveillance using the aerial TIRmethod for a few hours after sunrise, and again for a few hours before sunset.

The morning period is comparable to the flight times generally selected forvisual aerial survey, indicating the potential for combining these surveytechniques.

Camel behaviour is influenced by a range of factors, including the time of day.In the summer camels were observed to be feeding on various forbs andshrubs between sunrise and mid morning. During midmorning and lateafternoon the camels remained couched on a smooth open patch of ground.They were then observed feeding again from early evening to sunset.

The movement of camels provides opportunities and potential risks formonitoring. Movement may assist in the visual differentiation of camels from the

background, however, if they move into vegetated areas, they may be obscuredfrom visual counts resulting in increased visibility bias. Results from thisresearch have indicated that thermal signatures could be distinguished throughthe vegetation present in the trial sites. It appears therefore, that aerial TIR alsoprovides an opportunity to reduce the risk of visibility bias.

Conclusion

Recent advances in TIR technologies and the ability to interpret resulting digitaldata provide opportunities for improved aerial survey of camels and potentiallyother large warm blooded species.

This research has identified several key findings in relation to the use of aerialTIR for the survey of camels. It was discovered that it is important to knowabout the morphological, physiological and behavioural characteristics of thetarget species and to optimise operational parameters to enable detection viaits TIR signature. Camera type, angle, altitude, time and direction of datacapture were also found to be crucial to the detection and differentiation ofcamels in the landscape.

The mounting of Thermal InfraRed (TIR) sensors to aircraft to act as a fourthelectronic observer to calibrate visual observers or to eventually replace visualobservers shows real potential. If TIR can be developed operationally to meet

all survey requirements it may present a credible future alternative to manyexisting visual survey methods. As an alternative survey method, airborne TIRmay be more rapid, automated, cost effective, and safer than current visualaerial survey methods.

Initial results from the custom-developed Camel Finder Software demonstratedthat when combining the shape, size and temperature of camels this softwarewas able to highlight their presence while excluding other features in the image,including those of a similar temperature. Effectively, a minimal difference of2

oC is sufficient to detect and differentiate camels within the images obtained.

The software also demonstrated the ability to count selected features in the


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image, to georeference and convert them into a format for use within aGeographical Information System (GIS).

In the short term the opportunity for aerial TIR to be undertaken in combinationwith an operational visual aerial survey method is recognised. This has thepotential to immediately improve visual survey outcomes by addressingperception bias and other error estimates.

Acknowledgments

The authors acknowledge the funding and support provided for the project bythe Department of Water Land and Biodiversity Conservation.

The authors also wish to thank FLIR systems for the provision of the A320 FLIRthermography camera, as this ongoing support made the research possible.Acknowledgement is also given to the owners of Todmorden Station and

Beltana Station in South Australia for allowing us to utilise their properties forthe purposes of this study.

References

Bonython, C. W. 1989. Introduction and overview. In, The Great Filling of LakeEyre in 1974. Eds. Bonython, C. W. & Fraser, A. S. Royal Geographical Societyof Australasia, South Australian Branch, Adelaide.Costa, G., 1995, Behavioural Adaptations of Desert Animals. Berlin Heidelberg,Springer-Verlag.

Department for Primary Industries and Resources SA, 1996, Land Resources

Land Systems (Spatial Data), Metadata Available online at:http://www.asdd.sa.gov.au/asdd/ANZSA1002000027.htmlGrierson, I.T., and Gammon, J.A., 2002, The use of Aerial Digital Imagery for

Kangaroo Monitoring. Geeocarto International, 17(2), pp.45-52.

Grigg, G., Beard, L., Drges, B., Heucke, J., Coventry, J., Coppock, A.,Blomberg, S., 2009, Strategic (adaptive) hypothermia in bull dromedary camels

during rut; could it increase reproductive success? Biology Letters, 5(6),pp.853-856Higgins, A., 1986, The camel in health and disease. Bailliere Tindal, Sydney.

Jenson, J.R., 2007, Remote Sensing of the Environment An Earth Resource

Perspective, 2nd

edn, Pearson Prentice Hall, Upper Saddle River, NJ 07458.

Manefield, G., and Tinson, A., 1997, Camels, A compendium. University ofSydney Post Graduate Foundation in Veterinary Science, Sydney.

Lethbridge, M. and Pitt, J. (2009). Feral camel survey in the Nullarbor regionJune 2009: A discussion of survey outcomes and methods to inform landmanagement for protection of environmental assets. Alinytjara Wilurara NaturalResources Management Board, SA

Locke, S.L., Lopez, R.R., Peterson, M.J., Silvy, N.J, and Schwertner, W.T.,2006, Evaluation of portable infrared cameras for detecting rio grande wild

Turkeys. Wildlife Society bulletin, 34(3) pp. 839-844.


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Willmer, P., Stone, G., and Johnston, I., 2005 Environmental physiology ofanimals. 2nd Ed. Blackwell Publishing Ltd, Australia.

Wilson, R. T., 1984, The Camel. Essex, Longman.

Wilson, R.T., 1989, Ecophysiology of the Camelidae and Desert Ruminants.Berlin Heidelberg, Springer-Verlag.

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