It’s 20:30 and I have a dawn bat survey tomorrow (or is that tonight, I never quite know) with the alarm set at 01:50 – midsummer in the Highlands brings an early dawn. So apologies if this is little rushed, but if I don’t do it now, another week or three will pass.
Since going freelance some seven years ago now, one of the things I wanted to do was use technology to increase the effectiveness and robustness of the survey work I do. I was never a fan of coloured pencils on large scale maps, if I’m honest. Technology is most certainly not the answer to all woes and although I try, I would be lying if I said that all my tech investments were problem led rather than technology led. To date investments in field computing, bat detectors, IR night vision cameras, camtraps, commercial weather stations and a host of mostly useful software, have all been a relatively straightforward decision with a pretty quick ROI. However, this winter I was toiling with the investment in a thermal imaging device – a much more costly and more difficult to justify business case, in my opinion.
I should back up a bit and just point out that my ecological business has three main components; the standard protected species and habitat surveys for a range of clients large and small; provision of GIS services to other consultants and organisations; and aerial imaging and mapping with the use of UAVs (drones).
I have been doing the latter for a good few years now and undertake a variety of work focussing on ecological and environmental applications. I am not a drone services company as such, I am an ecologist who uses a drone as a tool to provide a broad range of services. This is relevant to my final choice of equipment.
So when the plan of investing in a thermal imaging device came to the fore, the two main criteria were, good resolution for terrestrial based bat survey work and capable of being used on a drone to enable additional services to be offered. To cut a long story short this narrows the search down dramatically to only a few and I started seriously looking at the Flir A65 series (taking into account the additional problems with respect to using laptops etc in the field), but this would mean that I would need a new drone to utilise the device to its maximum potential. There were drones with thermal imaging cameras available but utilising these on the ground for bat surveys would be cumbersome (as the drones were relatively large) and difficult and the thermal imaging cameras that were present could not be used disconnected from the drone. As I was coming to the conclusion that it would have to be the thermal imaging first and then the drone to carry it a year or two later, DJI (the dominant drone manufacturer) released information about a new drone – the Mavic 2 Enterprise Advanced (M2EA).
The M2EA is a small drone, easily fits in a shoebox when folded up. There was an earlier model with thermal imaging camera but the resolution was poor and would not have been of much use on the ground or in the air. The specs for the M2EA are available on the DJI website so I won’t repeat here, but the key features of the thermal imaging sensor is an Uncooled VOx Microbolometer with a resolution of 640×512 @30Hz and an accuracy of ±2℃. It records radiometric JPEGs but not radiometric video. The sensor is DJI made as they no longer use FLIR products but DJI have produced some amazing technology to date so I was not too worried. The decision basically came down to should I pay £5-6K for a quality thermal imaging device which I will also need to buy peripherals for and a new drone at around £12K to get it in the air… or pay £6K for the M2EA.
After a fair amount of discussions with sales reps, the M2EA did seem to tick all the boxes I needed (more or less) but was definitely not designed for my main use case – bat surveys on the ground. Slightly pushed by end of tax year implications I made the jump at the end of March and after a tortuous wait received the M2EA at the end of April, just in time for the bats.
So how does it perform for terrestrial bat surveys?
Positive points…
The drone has an HD optical camera alongside the thermal imager and records both simultaneously – this can be very useful in some cases.
I have hired a number of different FLIR systems over the years for specific jobs and in my opinion the thermal image is as good as any FLIR I’ve used at the same resolution.
As it is a drone it is simple to have multiple batteries and switch them out quickly, but the device can run for 2.5 hours off one battery so this is generally not an issue.
Storage wise, large capacity micro SD cards can be used and there is also an internal memory which can be used in an emergency.
Perhaps one of the best bits about the device is the controller. As it is a drone the controller provides a view of the sensors (you can switch between thermal, optical or split screen). This allows you to monitor what the camera is seeing and recording from the other side of the Site (assuming you are happy to leave your equipment unattended). In addition the controller enables you to move the camera by pointing to a location on the image. This enables repositioning of the field of view or scanning the area remotely. You can also switch from recording video to taking stills if required. The range of movement is excellent with almost 180 degree left and right and a significant movement up above the horizontal. It is slightly difficult if you need to point the camera up sharply, but not vertical as the movement of the camera is in relation to the horizontal of the ground not the drone as when inflight the drone is not going to be heavily angled. You can point the drone straight up and the camera will then go into a position lock mode pointing straight ahead relative to the drone which is useful for some inspection and survey work.
I have found it will pick bats up easily at up to 25-30m depending on conditions and now use it almost every survey as either a survey point (in certain circumstances) or as a backup for surveyors at key locations (roosts, potential roosts etc.)
Negative points
No radiometric video but to be honest this would be very data heavy and generally not needed for consultancy work.
It’s a bit more fiddly to setup compared to a standard hand held but it is possible to purchase brackets to allow the drone to be mounted on a tripod and in turn this could also be mounted on a taller pole if required (this is how I generally use it).
It has no significant protection against weather so you will not want to be using it when raining – although generally this avoided for the surveys anyway. It is also less robust than standard handheld units so you need to be careful not to drop it while stumbling around in the dark.
The standard setting has large flashing LEDs but these can be set to turn off when recording so is not too much of a problem.
The recording times out at just under 30mins but can be instantly restarted if storage space allows. Strangely the actual file length for one 29min recording gets split into three (two 13mins approx and then the rest as a third file - not sure why this is). It also beeps on the controller to tell you it has stopped so you are aware and can restart.
Interference with my Echo Meter Touch devices only occurs within about 0.3m so this causes no major issue if using detectors nearby, you just need a little separation.
There is an internal fan that comes on for periods of about 1 min every so often. It’s a little annoying but not really and is quieter than the standby noise of a Phantom 4 for example. It certainly isn’t loud enough to impact on surveying even if you are standing next to it.
There are a number of standard colour palettes that you can choose from but you have no control over the range of the colour palette. This is probably the most significant negative as far as I can tell. The imager will decide what it thinks is the best range to use and will change as the cameras field of view is changed. This may be improved in software updates which are generally relatively frequent on drones as they improve the experience.
The field of view is relatively narrow for bat surveys but in most cases I have not found this to be an issue. There is no spec on the actual FOV but through using FOV calculators it appears to be about 42°. If I get time I’ll try and work this out accurately in the field.
It is perhaps also worth pointing out that there is a good RGB camera on this device as well which for daylight operations is a great bonus. The device is sold with a ‘optical and digital zoom) but strangely the photos stored when a picture is taken do not have the zoomed in image. This has been a major issue with drone service providers who want to capture the zoomed in imagery, but as an ecologist this is not a major issue. This may be resolved as a software update but is likely to remain unchanged as may be a limit to push the high end customers to buy the bigger more expensive kit. The RGB sensor is also sold as a 48mp camera which is not really the case, it uses some DJI wizardry to essentially combine four 12mp images. It is still a good camera with a good zoom nonetheless.
As far as looking at the readiometric jpgs is concerned, you have to use DJIs (free) software which arguably is significantly poorer than the FLIR software, but I suspect that this will change over time as they improve the customer experience on this new equipment.
M2EA Ecological Applications
I have put together a few short clips from recent surveys that may be of use to establish whether or not the M2EA is for you. My main message would be if you are wanting to invest in thermal imaging and also fly or have committed to fly drones as well then it really is a no brainer. However, if the use of drones are not on your list of services then I would probably stick with one of the higher end handheld devices as these are likely to offer slightly better performance purely on the thermal imaging side of things. It is worth pointing out that the M2EA is actually a very good little drone that could be used for a whole host of other applications both thermal and optical. To date I have used the system professionally for assessing seals at haulouts, monitoring deer, rabbit surveys and countless bat surveys. I am also in discussions with clients looking to undertake other bespoke wildlife applications.
Feel free to get in touch to discuss.
