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An automated camera system for remote monitoring in polar environments
Cold Regions Science and Technology 55 (2009) 47–51
Contents lists available at ScienceDirect
Cold Regions Science and Technology j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / c o l d r e g i o n s
An automated camera system for remote monitoring in polar environments Kym B. Newbery ⁎, Colin Southwell Department of the Environment, Water, Heritage and the Arts, Australian Antarctic Division, Channel Highway, Kingston, Tasmania 7050, Australia
A R T I C L E
I N F O
Article history: Received 21 February 2008 Accepted 1 June 2008 Keywords: Digital camera Automated photographic remote monitoring
A B S T R A C T There is widespread recognition of the benefits in automating procedures for the collection of scientific data, and an increasing ability to do so as technology advances. The benefits are particularly relevant to long term monitoring programs in remote areas such as the polar regions where the costs of regularly accessing sites for repeated data collection are high. We describe the design and use of a camera system for automated recording of digital images at remote sites in polar environments. The design placed emphasis on low maintenance, low environmental impact, autonomous operation, and the ability to withstand high winds and low temperatures with very low electrical power requirements. Our motivation for designing the system was to facilitate monitoring of some aspects of Adelie penguin breeding biology, such as breeding chronology and chick survival, at multiple remote islands off the Antarctica coast. However, the system also has potential for application to other monitoring programs in polar environments. Crown Copyright © 2008 Published by Elsevier B.V. All rights reserved.
1. Introduction There is widespread recognition of the benefits in automating procedures for the collection of scientific data (Claridge et al., 2004, Hinkler et al., 2002), and an increasing ability to do so as technology advances. The benefits are particularly relevant to long term monitoring programs in remote areas such as Polar Regions where the costs of regularly accessing sites for repeated data collection are high. Images are increasingly being used as a means of capturing a wide range of monitoring data. Examples include images taken from satellites to monitor polar ice and snow (Massom, 1995), live aerial video images to monitor wildfires (Hice and Young, 1995), and images taken from still cameras to monitor wildlife populations (e.g. Brooks, 1996, York et al., 2001, Locke et al., 2005). We describe the design and use of a camera system for automated recording of digital images at remote sites in polar environments. The design places emphasis on low maintenance, low environmental impact, autonomous operation, ability to withstand high winds and low temperatures with very low electrical power requirements. Our motivation for designing the camera system was to facilitate monitoring of some aspects of Adelie penguin breeding biology, such as chronology and chick survival, at multiple remote islands off the Antarctica coast. In many regions of Antarctica, the islands that are occupied by breeding penguins are accessible early in the breeding period (early summer) when firm sea-ice allows easy travel, but are inaccessible or very difficult to access later in the breeding period (late summer) when the sea-ice has disappeared. Monitoring of Adelie penguin breeding performance has been carried out at Bechérvaise ⁎ Corresponding author. E-mail address: [email protected] (K.B. Newbery).
Island in east Antarctica since 1990 as part of the CCAMLR Ecosystem Monitoring System (Clarke et al., 2002). The use of manual observation methods, the need to be present regularly and frequently throughout the breeding period to apply these methods, and the logistical constraints to travel at some times of the year, have limited the spatial extent of monitoring that is possible by a small team to this single island. The aim of developing the camera system was to allow more spatially extensive and cost-effective monitoring of Adelie penguin breeding biology without the need for additional field workers or complex and expensive logistics. 2. Camera system description The camera system comprises seven main components: a digital single lens reflex (DSLR) camera, a camera controller, a weather-proof case, an external protective shutter, a solar panel and battery, a tripod with azimuth/elevation control, and rock mats for securing the tripod to the ground (Fig. 1). 2.1. DSLR camera The concept of the described camera system has only become realisable with the widespread availability of consumer digital cameras capable of taking images with quality approaching traditional 35 mm film. There are many specifications attached to digital cameras, however the two specifications of primary importance for our application are image quality and the ability to operate in low temperatures. At the time of writing, DSLR cameras have maximum image sensor pixel counts ranging from 6 to 21 Mega-pixels, although their cost rises almost exponentially above 10 Mega-pixels. Images are stored in the industry standard Joint Photographic Experts Group (JPEG) image
0165-232X/$ – see front matter. Crown Copyright © 2008 Published by Elsevier B.V. All rights reserved. doi:10.1016/j.coldregions.2008.06.001
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K.B. Newbery, C. Southwell / Cold Regions Science and Technology 55 (2009) 47–51
the camera needed to take pictures at sufficiently high quality to allow the images to be later viewed and the same information extracted as if a field observer were making direct observations. Specifically, we planned to use a single camera system to observe approximately 40 Adelie penguin nests in an area of around 40 m2, with the purpose of reliably determining whether an adult and/or chick is present or not at each of the nests on any day within a specified period of the breeding season. In addition, the camera needed to operate effectively during the summer months in temperatures down to −20 °C, and to be unaffected by temperatures as low as −35 °C when hibernating in the winter months. While we successfully used and tested Canon™ EOS-300D/Rebel and EOS-350D/Rebel XT DSLR cameras in developing the system, there would be numerous other suitable camera brands and models available, however each particular model needs to be tested for its ability to operate outside the manufacturers guaranteed operating temperature range. 2.2. Camera controller
Fig. 1. Camera system diagram.
file format and this format supports the Exchangeable Image File Format (EXIF) standard to embed metadata such as date and time, shutter speed, aperture and focal length into the image file. Most digital cameras also embed their serial number into the image which enables the images to be traced back to a specific camera (this may especially useful if several cameras and many images are being managed). For our purpose of monitoring penguin breeding success,
The camera controller performs all the automation functions required to make the camera system operate, particularly the frequency and timing of camera operation. Through the controller, the camera can be programmed to take an image at any specified minute in a year. Year information is not considered so that the program can repeat continually over successive years. To simplify the programming task, the camera system uses a programming method that allows use of wildcards for the month, day, hour and minute. The controller consists of a very low power microcontroller, based on the Texas Instruments MSP430 CPU and custom software. It contains a temperature compensated clock which remains accurate to better than 1 min in 1 year of operation at temperatures down to −40 °C. The minimum time resolution is limited to 1 min because of the inherent time variation in the picture taking process. This variation is the time it takes to turn on the camera, open the shutter, expose the image and write it to a memory card. The controller consumes very little power in sleep mode (80 μA at 12 V). When operating the camera, the power
Fig. 2. Camera controller block diagram.
K.B. Newbery, C. Southwell / Cold Regions Science and Technology 55 (2009) 47–51
consumption is dominated by the DSLR and shutter servo motor. These components are only operated as long as necessary to take a picture. The camera controller also has two buttons “picture” and “power” located on the rear of the weather-proof case. These external buttons allow test pictures to be taken once the camera is setup, and to manually turn on the camera to check its operation. Fig. 2 shows a block diagram of the controller. The controller is housed in a plastic enclosure inside the weather-proof case. It has been designed to be easily removed and replaced if required. The controller is complicated by the need for 3 separate power supplies; 3.3 V is required for the MSP430 CPU and logic, 6 V at 1 Amp maximum is required for the servo motor, and 7.5 V at up to 2 Amp maximum is required for the DSLR camera. The CPU has the ability to turn the 6 V and 7.5 V supplies on and off when required. The CPU has a serial command port which is used to program the controller using a laptop PC. The controller has red and green lights for diagnostic purposes to help when setting up the camera in the field. The lights indicate that the controller has detected no problems with the clock, camera program or battery voltages, allowing the user to be confident that the camera will take photographs after it has been installed. 2.3. Weather-proof case The camera and camera controller are enclosed in a standard Pelican™ brand case (type 1300), to protect them from hostile weather conditions (Fig. 3). This style of case makes a good allweather outdoor enclosure because the plastic is UV resistant and retains its strong properties when cold. Use of black-coloured plastic also assists with snow and ice removal because it seems to warm up faster in sunlight compared to other colours. The case has a lid which effectively seals with hand operated snap-locks allowing easy access the camera with gloved hands and without the need for tools. Condensation can form inside the case during warm weather so a sachet of desiccant is kept inside the case to absorb moisture. The desiccant has only needed to be de-hydrated every 12 months. 2.4. External protective shutter The case has an optical window on one side through which images are taken. When the camera is not in operation, the window is covered with an externally-mounted protective shutter to keep the window from being abraded by dust and snow. The shutter has a set of bristles that form a snow proof seal around the window and which also brush the window clean when the shutter is opening and closing (Fig. 4). Just
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Fig. 4. View of the protective shutter partially open, illustrating bristle cleaning.
before the camera takes an image, the shutter rotates to expose the window and then after the image has been taken the shutter closes. The shutter mechanism is based on a servo motor which provides high torque at low power in a sealed and easily operated package. The controller automatically limits the power to the servo motor and only applies power for short periods, minimising power use and preventing damage to the servo motor if the shutter has been jammed by a heavy icing event. In our experience, the servo motor has always had enough torque to dislodge ice and debris without damage to the motor. 2.5. Solar panel and battery Solar and wind power are the two most viable sources of renewable energy in polar regions, and of those two, solar power requires the least amount of infrastructure and is the most reliable. By focusing design effort into lowering the power consumption of the camera system, the size and mass of the solar panel and batteries can be greatly reduced. Low power also rules out any kind of electrical heating, so all components must be able to function at the required temperatures. An analysis of the camera system power consumption showed that our maximum possible requirement (10 images a day for 160 days a year) required only a modest battery and solar panel combination; a 12 V, 2.5 Ah battery in combination with a 5 W solar panel was selected. The analysis included temperature de-rating at −30 °C where the battery capacity drops to 30% of its nominal value. Battery self-discharge and controller quiescent consumption was also included. Attention was paid to low temperature performance, long term trickle charging, rugged construction and a non-liquid electrolyte to avoid freezing failure and problems with transport of hazardous materials. The EnerSys™ Cyclon family pure lead-tin batteries fitted all these criteria. A simple, voltage adjustable, series regulator was chosen to regulate the charge into the batteries from the solar panel. The regulator was also selected for negligible battery discharge in the long periods where there is no solar power available. Both the battery pack and solar regulator are contained in a plastic box, which in turn is located in a small carry bag which both protects the plastic box from UV light degradation and is a practical carrying device. The solar panel, which is flexible but still stiff, is tied to the tripod legs using shock absorbing ‘bungy’ cord. 2.6. Tripod
Fig. 3. Camera system overlooking a penguin colony near Mawson Station, east Antarctica.
The tripod is a 3 legged, surveyors' tripod with the legs shortened to a length of 700 mm. The tripod is made from light-weight aluminium with spiked tips and fastening points at the ends of the feet to which the rock mats are attached. A custom made heavy duty azimuth and elevation wedge bracket allows the camera enclosure to be adjusted to point in almost any direction. Once tightened it is able to withstand the mechanical stresses of high winds.
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K.B. Newbery, C. Southwell / Cold Regions Science and Technology 55 (2009) 47–51
2.7. Rock mats The camera system needed to be secured and free of vibration in the face of winds in excess of 200 km/h. Also, in keeping with the spirit of the Protocol on Environmental Protection to the Antarctic Treaty, and because of our desire to monitor penguins as unobtrusively as possible, the mechanism to secure the camera system was designed to have as little environmental impact as possible. The securing mechanism comprises a heavy-grade plastic mat secured to the tripod feet. Heavy rocks are placed on the rock mats and around the feet. Hence no rock holes are required for guy wires, no foreign materials are left behind after the camera is removed, and the only environmental impact is the movement of the rocks located near the camera site.
wind, which tends to keep the camera system free of snow and stops it being buried in blizzard tails forming down wind of rocks and in sheltered spots. The solar panels should be orientated towards true north for maximum effect. At high latitudes the panels need to be near-vertical to achieve maximum effect, but this usually results in high wind loading and vibration. Wind loading can be reduced by fixing the panel as low to the ground as possible and piling rocks on the windward side of the panel. Once set up, the camera system is designed to remain in place through several Antarctic summers and winters with only the need for a once-yearly maintenance and download. 5. Field testing
3. Storing and downloading images The ability to remotely download images by wireless or wired methods is attractive; however there are several reasons why this capability has not yet been incorporated into the system. Longdistance radio or satellite links in hostile environments add a considerable level of complexity, power consumption and cost. Often the effort required to install and maintain a communications link can exceed the effort to visit the remote site periodically. Being able to access high quality pictures remotely is also problematic. For example, a typical high quality image from an eight Mega-pixel camera, JPEG compressed to 3 MB, would take at least 55 min, and would be very expensive to transfer over an Iridium™ modem link at 9600 bits per second. Even if the purpose of the communications link was to transfer only small thumbnail versions of the images collected, the ability to download the images from the DSLR and then generate the thumbnail sized images depends on a suite of technologies that is complex and challenging to implement in remote and low power systems. We chose instead to store the images on a memory card and ‘manually’ download the images by visiting the site at infrequent intervals when access was easiest (eg during winter when sea-ice is extensive and reliable) and swapping the full card with an empty one. The storage capacity of the memory card depends on several factors, including the complexity and file size of the images, the amount of image compression applied and the number of images taken between memory card exchanges. By assuming the worst case for all these parameters, a memory card of 2 GB was chosen. 4. Transport and setup For our application the primary regions of operation are Antarctic coastal islands where Adelie penguins breed. Vehicle access over seaice to the islands of interest varies with the quality of sea-ice, the time of year and the distance to be travelled. There are some sites where poor sea-ice limits vehicle access year round, necessitating access by either helicopter or foot/ski. Consequently, the camera system was designed to be as light-weight and portable as possible so as to be suitable for all transport options. Without the rocks, the camera system weighs about 20 kg and can fit in a large backpack. It can be easily carried on a quad (four-wheel drive motor bike), in a Hagglunds (tracked vehicle) or in a helicopter, and can also be easily carried by hand from a vehicle to the operating site. The camera system is able to be setup and tested in no more than 30 min and does not require any custom tools. The mechanical construction uses standard metric fasteners. A small set of hex keys and spanners is left with the system so that there are no tools to bring on future visits. Site selection is important. A good site consists of a relatively flat and stable rock covered surface. Rocky moraines are also suitable if there is a large bed of rocks that will not sink into the surrounding snow. It has been found that good sites are those that are exposed to
Antarctic conditions can be hostile and extremely taxing on any form of equipment. In our application, adverse conditions included extreme cold, wind speeds in excess of 200 km/h, blowing snow, ice, dust, grit and salt spray. Antarctic winds in particular can cause material failure from the unrelenting vibration of loose cables and fixtures. It was therefore essential to test the camera system thoroughly in the field before routine use. The system was tested at Bechérvaise Island near Mawson station in east Antarctica (Fig. 3) over four austral summers (2004–05 to 2007–08) and the three intervening winters (2005 to 2007), and at Casey station in east Antarctica over two austral summers (2005–06 to 2006–07). Tests were also undertaken in a temperature controlled refrigerator. Testing in the first summer exposed a problem of static electricity causing many dark pictures to be taken during high winds. A modification to the camera controller firmware solved this problem. Some problems were also found in obtaining the correct exposure at low light levels and in temperatures below −20 °C. The reason for the fault was isolated to the camera exposure sensor not operating correctly at low temperatures. This is an issue which affects all electronics equipment to varying extents, and requires the controlled temperature testing of each camera model. The initial design for the protective shutter was successful in minimising abrasion damage on the lens window from blowing dust and wind, but did not completely stop snow and ice building up on the lens window. Subsequent refinements of the design have addressed this problem by incorporating bristles that brush the lens clear of snow when opening and closing as well as forming a seal when the shutter is closed (Fig. 4). In all of the summer trials, when cameras were programmed to take ten photographs each day for three months, the available solar power far exceeded the required power. In the winter trials, available power was sufficient for the cameras to take a single photograph each day from February through to December, and thereafter begin taking ten photographs each day in the following summer. Despite operating in winds of up to 200 km/h over periods of many months, none of the images were blurred from vibration of the camera, and the camera's field of view was constant, indicating there was no movement or change in orientation of the tripod or camera case. 6. Limitations While we consider the system is now developed for routine operation in the field, further improvements and developments are possible. The presence of two clock sources (one in the camera controller and one in the camera itself) means that the time-stamps in the image metadata drift slightly due to the drift from both clock sources (although the actual time the picture is taken is still controlled by the more stable controller clock). Depending on the amount of wind vibration, the DSLR lens elements can move slightly out of focus over time. A solution to this problem is to leave the lens in auto-focus mode at the risk of possible missed images during blizzards or when there are very low contrast subjects.
K.B. Newbery, C. Southwell / Cold Regions Science and Technology 55 (2009) 47–51
Making observations from camera images will always have some limitations in comparison with direct, manual observations. However, being able to make frequent observations in a cost-effective manner over multiple sites that are often inaccessible is a major advantage for monitoring programs in Polar Regions. The camera system is also likely to be suitable for monitoring programs other than the one it was specifically developed for; for example, since its development it has also been used to monitor the break-out of fast ice in areas of east Antarctica. 7. Future developments Developing a satellite modem to automatically download images from the DSLR, resize them and then send images back from remote locations is a potential future development, but will require significant engineering design and field trials to make a low power, autonomous and reliable solution. Acknowledgements We thank Eric King for mechanical design and construction as well as numerous ANARE (Australian National Antarctic Research Expedi-
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tion) expeditioners for field maintenance trips to download and check the cameras. References Brooks, R.T., 1996. Assessment of two camera-based systems for monitoring arboreal wildlife. Wildlife Society Bulletin 24, 298–300. Clarke, J., Kerry, K., Irvine, L., Phillips, B., 2002. Chick provisioning and breeding success of Adélie penguins at Béchervaise Island over eight successive seasons. Polar Biology 25, 21–30. Claridge, A.W., Mifsud, G., Dawson, J., Saxon, M.J., 2004. Use of infrared digital cameras to investigate the behaviour of cryptic species. Wildlife Research 31, 645–650. York, E.C., Moruzzi, T.L., Fuller, T.K., Organ, J.F., Sauvajot, R.M., DeGraaf, R.M., 2001. Description and evaluation of a remote camera and triggering system to monitor carnivores. Wildlife Society Bulletin 29. Hice, C., Young, D., 1995. Real-time image analysis and visualization from remote video. Advanced Imaging 10, 30–32. Hinkler, J., Pedersen, S.B., Rasch, M., Hansen, B.U., 2002. Automatic snow cover monitoring at high temporal and spatial resolution, using images taken by a standard digital camera. International Journal of Remote Sensing 23, 4669–4682. Massom, R., 1995. Satellite remote sensing of polar ice and snow: present status and future directions. Polar Record 177, 99–114. Locke, S.L., Cline, M.D., Wetzel, D.L., Pittman, M.T., Brewer, C.E., et al., 2005. A web-based digital camera for monitoring remote wildlife. Wildlife Society Bulletin 33, 761–765.
Contents lists available at ScienceDirect
Cold Regions Science and Technology j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / c o l d r e g i o n s
An automated camera system for remote monitoring in polar environments Kym B. Newbery ⁎, Colin Southwell Department of the Environment, Water, Heritage and the Arts, Australian Antarctic Division, Channel Highway, Kingston, Tasmania 7050, Australia
A R T I C L E
I N F O
Article history: Received 21 February 2008 Accepted 1 June 2008 Keywords: Digital camera Automated photographic remote monitoring
A B S T R A C T There is widespread recognition of the benefits in automating procedures for the collection of scientific data, and an increasing ability to do so as technology advances. The benefits are particularly relevant to long term monitoring programs in remote areas such as the polar regions where the costs of regularly accessing sites for repeated data collection are high. We describe the design and use of a camera system for automated recording of digital images at remote sites in polar environments. The design placed emphasis on low maintenance, low environmental impact, autonomous operation, and the ability to withstand high winds and low temperatures with very low electrical power requirements. Our motivation for designing the system was to facilitate monitoring of some aspects of Adelie penguin breeding biology, such as breeding chronology and chick survival, at multiple remote islands off the Antarctica coast. However, the system also has potential for application to other monitoring programs in polar environments. Crown Copyright © 2008 Published by Elsevier B.V. All rights reserved.
1. Introduction There is widespread recognition of the benefits in automating procedures for the collection of scientific data (Claridge et al., 2004, Hinkler et al., 2002), and an increasing ability to do so as technology advances. The benefits are particularly relevant to long term monitoring programs in remote areas such as Polar Regions where the costs of regularly accessing sites for repeated data collection are high. Images are increasingly being used as a means of capturing a wide range of monitoring data. Examples include images taken from satellites to monitor polar ice and snow (Massom, 1995), live aerial video images to monitor wildfires (Hice and Young, 1995), and images taken from still cameras to monitor wildlife populations (e.g. Brooks, 1996, York et al., 2001, Locke et al., 2005). We describe the design and use of a camera system for automated recording of digital images at remote sites in polar environments. The design places emphasis on low maintenance, low environmental impact, autonomous operation, ability to withstand high winds and low temperatures with very low electrical power requirements. Our motivation for designing the camera system was to facilitate monitoring of some aspects of Adelie penguin breeding biology, such as chronology and chick survival, at multiple remote islands off the Antarctica coast. In many regions of Antarctica, the islands that are occupied by breeding penguins are accessible early in the breeding period (early summer) when firm sea-ice allows easy travel, but are inaccessible or very difficult to access later in the breeding period (late summer) when the sea-ice has disappeared. Monitoring of Adelie penguin breeding performance has been carried out at Bechérvaise ⁎ Corresponding author. E-mail address: [email protected] (K.B. Newbery).
Island in east Antarctica since 1990 as part of the CCAMLR Ecosystem Monitoring System (Clarke et al., 2002). The use of manual observation methods, the need to be present regularly and frequently throughout the breeding period to apply these methods, and the logistical constraints to travel at some times of the year, have limited the spatial extent of monitoring that is possible by a small team to this single island. The aim of developing the camera system was to allow more spatially extensive and cost-effective monitoring of Adelie penguin breeding biology without the need for additional field workers or complex and expensive logistics. 2. Camera system description The camera system comprises seven main components: a digital single lens reflex (DSLR) camera, a camera controller, a weather-proof case, an external protective shutter, a solar panel and battery, a tripod with azimuth/elevation control, and rock mats for securing the tripod to the ground (Fig. 1). 2.1. DSLR camera The concept of the described camera system has only become realisable with the widespread availability of consumer digital cameras capable of taking images with quality approaching traditional 35 mm film. There are many specifications attached to digital cameras, however the two specifications of primary importance for our application are image quality and the ability to operate in low temperatures. At the time of writing, DSLR cameras have maximum image sensor pixel counts ranging from 6 to 21 Mega-pixels, although their cost rises almost exponentially above 10 Mega-pixels. Images are stored in the industry standard Joint Photographic Experts Group (JPEG) image
0165-232X/$ – see front matter. Crown Copyright © 2008 Published by Elsevier B.V. All rights reserved. doi:10.1016/j.coldregions.2008.06.001
48
K.B. Newbery, C. Southwell / Cold Regions Science and Technology 55 (2009) 47–51
the camera needed to take pictures at sufficiently high quality to allow the images to be later viewed and the same information extracted as if a field observer were making direct observations. Specifically, we planned to use a single camera system to observe approximately 40 Adelie penguin nests in an area of around 40 m2, with the purpose of reliably determining whether an adult and/or chick is present or not at each of the nests on any day within a specified period of the breeding season. In addition, the camera needed to operate effectively during the summer months in temperatures down to −20 °C, and to be unaffected by temperatures as low as −35 °C when hibernating in the winter months. While we successfully used and tested Canon™ EOS-300D/Rebel and EOS-350D/Rebel XT DSLR cameras in developing the system, there would be numerous other suitable camera brands and models available, however each particular model needs to be tested for its ability to operate outside the manufacturers guaranteed operating temperature range. 2.2. Camera controller
Fig. 1. Camera system diagram.
file format and this format supports the Exchangeable Image File Format (EXIF) standard to embed metadata such as date and time, shutter speed, aperture and focal length into the image file. Most digital cameras also embed their serial number into the image which enables the images to be traced back to a specific camera (this may especially useful if several cameras and many images are being managed). For our purpose of monitoring penguin breeding success,
The camera controller performs all the automation functions required to make the camera system operate, particularly the frequency and timing of camera operation. Through the controller, the camera can be programmed to take an image at any specified minute in a year. Year information is not considered so that the program can repeat continually over successive years. To simplify the programming task, the camera system uses a programming method that allows use of wildcards for the month, day, hour and minute. The controller consists of a very low power microcontroller, based on the Texas Instruments MSP430 CPU and custom software. It contains a temperature compensated clock which remains accurate to better than 1 min in 1 year of operation at temperatures down to −40 °C. The minimum time resolution is limited to 1 min because of the inherent time variation in the picture taking process. This variation is the time it takes to turn on the camera, open the shutter, expose the image and write it to a memory card. The controller consumes very little power in sleep mode (80 μA at 12 V). When operating the camera, the power
Fig. 2. Camera controller block diagram.
K.B. Newbery, C. Southwell / Cold Regions Science and Technology 55 (2009) 47–51
consumption is dominated by the DSLR and shutter servo motor. These components are only operated as long as necessary to take a picture. The camera controller also has two buttons “picture” and “power” located on the rear of the weather-proof case. These external buttons allow test pictures to be taken once the camera is setup, and to manually turn on the camera to check its operation. Fig. 2 shows a block diagram of the controller. The controller is housed in a plastic enclosure inside the weather-proof case. It has been designed to be easily removed and replaced if required. The controller is complicated by the need for 3 separate power supplies; 3.3 V is required for the MSP430 CPU and logic, 6 V at 1 Amp maximum is required for the servo motor, and 7.5 V at up to 2 Amp maximum is required for the DSLR camera. The CPU has the ability to turn the 6 V and 7.5 V supplies on and off when required. The CPU has a serial command port which is used to program the controller using a laptop PC. The controller has red and green lights for diagnostic purposes to help when setting up the camera in the field. The lights indicate that the controller has detected no problems with the clock, camera program or battery voltages, allowing the user to be confident that the camera will take photographs after it has been installed. 2.3. Weather-proof case The camera and camera controller are enclosed in a standard Pelican™ brand case (type 1300), to protect them from hostile weather conditions (Fig. 3). This style of case makes a good allweather outdoor enclosure because the plastic is UV resistant and retains its strong properties when cold. Use of black-coloured plastic also assists with snow and ice removal because it seems to warm up faster in sunlight compared to other colours. The case has a lid which effectively seals with hand operated snap-locks allowing easy access the camera with gloved hands and without the need for tools. Condensation can form inside the case during warm weather so a sachet of desiccant is kept inside the case to absorb moisture. The desiccant has only needed to be de-hydrated every 12 months. 2.4. External protective shutter The case has an optical window on one side through which images are taken. When the camera is not in operation, the window is covered with an externally-mounted protective shutter to keep the window from being abraded by dust and snow. The shutter has a set of bristles that form a snow proof seal around the window and which also brush the window clean when the shutter is opening and closing (Fig. 4). Just
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Fig. 4. View of the protective shutter partially open, illustrating bristle cleaning.
before the camera takes an image, the shutter rotates to expose the window and then after the image has been taken the shutter closes. The shutter mechanism is based on a servo motor which provides high torque at low power in a sealed and easily operated package. The controller automatically limits the power to the servo motor and only applies power for short periods, minimising power use and preventing damage to the servo motor if the shutter has been jammed by a heavy icing event. In our experience, the servo motor has always had enough torque to dislodge ice and debris without damage to the motor. 2.5. Solar panel and battery Solar and wind power are the two most viable sources of renewable energy in polar regions, and of those two, solar power requires the least amount of infrastructure and is the most reliable. By focusing design effort into lowering the power consumption of the camera system, the size and mass of the solar panel and batteries can be greatly reduced. Low power also rules out any kind of electrical heating, so all components must be able to function at the required temperatures. An analysis of the camera system power consumption showed that our maximum possible requirement (10 images a day for 160 days a year) required only a modest battery and solar panel combination; a 12 V, 2.5 Ah battery in combination with a 5 W solar panel was selected. The analysis included temperature de-rating at −30 °C where the battery capacity drops to 30% of its nominal value. Battery self-discharge and controller quiescent consumption was also included. Attention was paid to low temperature performance, long term trickle charging, rugged construction and a non-liquid electrolyte to avoid freezing failure and problems with transport of hazardous materials. The EnerSys™ Cyclon family pure lead-tin batteries fitted all these criteria. A simple, voltage adjustable, series regulator was chosen to regulate the charge into the batteries from the solar panel. The regulator was also selected for negligible battery discharge in the long periods where there is no solar power available. Both the battery pack and solar regulator are contained in a plastic box, which in turn is located in a small carry bag which both protects the plastic box from UV light degradation and is a practical carrying device. The solar panel, which is flexible but still stiff, is tied to the tripod legs using shock absorbing ‘bungy’ cord. 2.6. Tripod
Fig. 3. Camera system overlooking a penguin colony near Mawson Station, east Antarctica.
The tripod is a 3 legged, surveyors' tripod with the legs shortened to a length of 700 mm. The tripod is made from light-weight aluminium with spiked tips and fastening points at the ends of the feet to which the rock mats are attached. A custom made heavy duty azimuth and elevation wedge bracket allows the camera enclosure to be adjusted to point in almost any direction. Once tightened it is able to withstand the mechanical stresses of high winds.
50
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2.7. Rock mats The camera system needed to be secured and free of vibration in the face of winds in excess of 200 km/h. Also, in keeping with the spirit of the Protocol on Environmental Protection to the Antarctic Treaty, and because of our desire to monitor penguins as unobtrusively as possible, the mechanism to secure the camera system was designed to have as little environmental impact as possible. The securing mechanism comprises a heavy-grade plastic mat secured to the tripod feet. Heavy rocks are placed on the rock mats and around the feet. Hence no rock holes are required for guy wires, no foreign materials are left behind after the camera is removed, and the only environmental impact is the movement of the rocks located near the camera site.
wind, which tends to keep the camera system free of snow and stops it being buried in blizzard tails forming down wind of rocks and in sheltered spots. The solar panels should be orientated towards true north for maximum effect. At high latitudes the panels need to be near-vertical to achieve maximum effect, but this usually results in high wind loading and vibration. Wind loading can be reduced by fixing the panel as low to the ground as possible and piling rocks on the windward side of the panel. Once set up, the camera system is designed to remain in place through several Antarctic summers and winters with only the need for a once-yearly maintenance and download. 5. Field testing
3. Storing and downloading images The ability to remotely download images by wireless or wired methods is attractive; however there are several reasons why this capability has not yet been incorporated into the system. Longdistance radio or satellite links in hostile environments add a considerable level of complexity, power consumption and cost. Often the effort required to install and maintain a communications link can exceed the effort to visit the remote site periodically. Being able to access high quality pictures remotely is also problematic. For example, a typical high quality image from an eight Mega-pixel camera, JPEG compressed to 3 MB, would take at least 55 min, and would be very expensive to transfer over an Iridium™ modem link at 9600 bits per second. Even if the purpose of the communications link was to transfer only small thumbnail versions of the images collected, the ability to download the images from the DSLR and then generate the thumbnail sized images depends on a suite of technologies that is complex and challenging to implement in remote and low power systems. We chose instead to store the images on a memory card and ‘manually’ download the images by visiting the site at infrequent intervals when access was easiest (eg during winter when sea-ice is extensive and reliable) and swapping the full card with an empty one. The storage capacity of the memory card depends on several factors, including the complexity and file size of the images, the amount of image compression applied and the number of images taken between memory card exchanges. By assuming the worst case for all these parameters, a memory card of 2 GB was chosen. 4. Transport and setup For our application the primary regions of operation are Antarctic coastal islands where Adelie penguins breed. Vehicle access over seaice to the islands of interest varies with the quality of sea-ice, the time of year and the distance to be travelled. There are some sites where poor sea-ice limits vehicle access year round, necessitating access by either helicopter or foot/ski. Consequently, the camera system was designed to be as light-weight and portable as possible so as to be suitable for all transport options. Without the rocks, the camera system weighs about 20 kg and can fit in a large backpack. It can be easily carried on a quad (four-wheel drive motor bike), in a Hagglunds (tracked vehicle) or in a helicopter, and can also be easily carried by hand from a vehicle to the operating site. The camera system is able to be setup and tested in no more than 30 min and does not require any custom tools. The mechanical construction uses standard metric fasteners. A small set of hex keys and spanners is left with the system so that there are no tools to bring on future visits. Site selection is important. A good site consists of a relatively flat and stable rock covered surface. Rocky moraines are also suitable if there is a large bed of rocks that will not sink into the surrounding snow. It has been found that good sites are those that are exposed to
Antarctic conditions can be hostile and extremely taxing on any form of equipment. In our application, adverse conditions included extreme cold, wind speeds in excess of 200 km/h, blowing snow, ice, dust, grit and salt spray. Antarctic winds in particular can cause material failure from the unrelenting vibration of loose cables and fixtures. It was therefore essential to test the camera system thoroughly in the field before routine use. The system was tested at Bechérvaise Island near Mawson station in east Antarctica (Fig. 3) over four austral summers (2004–05 to 2007–08) and the three intervening winters (2005 to 2007), and at Casey station in east Antarctica over two austral summers (2005–06 to 2006–07). Tests were also undertaken in a temperature controlled refrigerator. Testing in the first summer exposed a problem of static electricity causing many dark pictures to be taken during high winds. A modification to the camera controller firmware solved this problem. Some problems were also found in obtaining the correct exposure at low light levels and in temperatures below −20 °C. The reason for the fault was isolated to the camera exposure sensor not operating correctly at low temperatures. This is an issue which affects all electronics equipment to varying extents, and requires the controlled temperature testing of each camera model. The initial design for the protective shutter was successful in minimising abrasion damage on the lens window from blowing dust and wind, but did not completely stop snow and ice building up on the lens window. Subsequent refinements of the design have addressed this problem by incorporating bristles that brush the lens clear of snow when opening and closing as well as forming a seal when the shutter is closed (Fig. 4). In all of the summer trials, when cameras were programmed to take ten photographs each day for three months, the available solar power far exceeded the required power. In the winter trials, available power was sufficient for the cameras to take a single photograph each day from February through to December, and thereafter begin taking ten photographs each day in the following summer. Despite operating in winds of up to 200 km/h over periods of many months, none of the images were blurred from vibration of the camera, and the camera's field of view was constant, indicating there was no movement or change in orientation of the tripod or camera case. 6. Limitations While we consider the system is now developed for routine operation in the field, further improvements and developments are possible. The presence of two clock sources (one in the camera controller and one in the camera itself) means that the time-stamps in the image metadata drift slightly due to the drift from both clock sources (although the actual time the picture is taken is still controlled by the more stable controller clock). Depending on the amount of wind vibration, the DSLR lens elements can move slightly out of focus over time. A solution to this problem is to leave the lens in auto-focus mode at the risk of possible missed images during blizzards or when there are very low contrast subjects.
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Making observations from camera images will always have some limitations in comparison with direct, manual observations. However, being able to make frequent observations in a cost-effective manner over multiple sites that are often inaccessible is a major advantage for monitoring programs in Polar Regions. The camera system is also likely to be suitable for monitoring programs other than the one it was specifically developed for; for example, since its development it has also been used to monitor the break-out of fast ice in areas of east Antarctica. 7. Future developments Developing a satellite modem to automatically download images from the DSLR, resize them and then send images back from remote locations is a potential future development, but will require significant engineering design and field trials to make a low power, autonomous and reliable solution. Acknowledgements We thank Eric King for mechanical design and construction as well as numerous ANARE (Australian National Antarctic Research Expedi-
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tion) expeditioners for field maintenance trips to download and check the cameras. References Brooks, R.T., 1996. Assessment of two camera-based systems for monitoring arboreal wildlife. Wildlife Society Bulletin 24, 298–300. Clarke, J., Kerry, K., Irvine, L., Phillips, B., 2002. Chick provisioning and breeding success of Adélie penguins at Béchervaise Island over eight successive seasons. Polar Biology 25, 21–30. Claridge, A.W., Mifsud, G., Dawson, J., Saxon, M.J., 2004. Use of infrared digital cameras to investigate the behaviour of cryptic species. Wildlife Research 31, 645–650. York, E.C., Moruzzi, T.L., Fuller, T.K., Organ, J.F., Sauvajot, R.M., DeGraaf, R.M., 2001. Description and evaluation of a remote camera and triggering system to monitor carnivores. Wildlife Society Bulletin 29. Hice, C., Young, D., 1995. Real-time image analysis and visualization from remote video. Advanced Imaging 10, 30–32. Hinkler, J., Pedersen, S.B., Rasch, M., Hansen, B.U., 2002. Automatic snow cover monitoring at high temporal and spatial resolution, using images taken by a standard digital camera. International Journal of Remote Sensing 23, 4669–4682. Massom, R., 1995. Satellite remote sensing of polar ice and snow: present status and future directions. Polar Record 177, 99–114. Locke, S.L., Cline, M.D., Wetzel, D.L., Pittman, M.T., Brewer, C.E., et al., 2005. A web-based digital camera for monitoring remote wildlife. Wildlife Society Bulletin 33, 761–765.