©The Deer Initiative |
Thermal Imaging is a term that describes taking pictures or video using light, or more correctly electromagnetic radiation, of a longer wavelength than we can see with our eyes. This is known as InfraRed and we normally experience this as heat.
A Thermal Imager is able to make images in shades of grey where the warmer parts of the scene are lighter and cooler parts darker. Although these devices were created for suveillence and warfare they are ideal for locating and consequently counting warm things like deer in cool places.
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The ideal situation is to use these imagers in as open space as possible and when it is cool. As no visible lights are required, viewing and counting deer at night offers the best temperature contrast and least disturbance of the deer thus better avoiding double counting if herds don’t move.
Thermal imaging was used as an adjunct to the daytime count not as a means of replacing it. Both are valuable in their own way – the more information the better.
There are a number of ways to interpret the images recorded using these thermal images and they depend on many factors including the terrain, the number of viewing points etc. and also options for the use of smart software to identify, count and avoid double counting.
However the approach taken with our first ‘Thermal Count’ took advantage of very detailed local knowledge, as does our the daytime count, with a guide present at all times, and, using a vehicle carrying the imager, moved quickly from place to place in a way designed not to push deer into the uncounted areas. The method is very quick to achieve a count and because the method uses no spotlight, the deer are left undisturbed and invariably will still be in roughly the same place some time later – low deer disturbance and more accurate counting.
©The Deer Initiative |
Interestingly, although the count area included extensive areas of woodland (and deer could be seen very well in them, the deer showing up so well) more than 99% of the deer seen were in the open. This is commonly the case with fallow deer at night as it is often the only time that they can graze in peace.
To ensure a consistent tally the counters note any deer that might have been double counted are discounted so numbers quoted from such counts are therefore the known, absolute minimum. No estimates of the proportion of hidden deer nor extrapolation for unviewed areas, keeping the numbers to be the minimum actually viewed deer.
See also the web-site of The Deer Initiative.
