Animal Count Example Park 1 12/31/2001
The aerial infrared imaging flight for Example Park 1 was conducted
between 2248 on 26 December and 0045, 27 December 2001. Imaging conditions
were good. Surface winds were from 220 degrees at seven miles per hour,
with winds at the imaging altitude of 1500 feet above ground level (AGL)
from 250 degrees at ~15 mph. The ground was covered with 2-4 inches
of snow that was about two days old. Average air temperature was –7
deg. C. The cloud ceiling was broken at 9000 feet AGL, with two scattered
layers below. A very light snow was falling during portions of the flight
and there was light to moderate turbulence from beginning to end.
Animal Count Example Park 2 12/31/2001
The infrared imaging flight of Example Park 2 was conducted between
2255 on 31 December and 0128, 1 January 2002. Imaging conditions were
excellent and small animals were easily visible on the ground and in
the trees. Surface winds were initially from 210 degrees at five miles
per hour, later changing to 200 at 10 mph. Winds at the imaging altitude
of 1500 feet AGL were WSW at about 10 mph. The ground was covered with
a few inches of snow that fairly fresh. Average air temperature was
–9 deg. C. The sky condition was clear with no turbulence.
Equipment, Flight Methodology, Analysis Methodology
This example count was accomplished with a single-engine airplane and
using a high-resolution thermal imager oriented ‘looking’
straight down through a camera hole in the belly of the airplane. The
counts were flown at an average altitude of 1500 feet above ground level
with the camera view directly below the airplane. After the flight,
we analyzed the videotape using a TV monitor and a computer.
To count the deer, we watch the entire tape, pausing and playing it
backward and forward at regular speed and in slow motion, as necessary.
Generally, for each hour of tape, three or more hours of analysis and
reporting are required to complete the count. As we view the tape and
note the deer, we mark each one as a dot on a computer version of the
maps accompanying this report. When we have viewed the entire tape,
we count the dots on the map to find the number of deer in the count
area. If we note large domestic animals on the computer map, we mark
them with a different color dot. In these counts, red dots denote deer,
gray or yellow dots (if any) denote possible deer or other unknown animal
similar in size to a deer but apparently not a deer and blue dots (if
any) represent domestic animals such as cattle, sheep or horses. These
animals are always much warmer and in the case of horses and cattle,
substantially larger than any deer.
Deer usually appear as a fairly bright white dot or narrow line (similar
to a grain of rice) in the infrared imagery. In this imagery, white
and lighter shades of gray represents warmer objects while black and
darker shades of gray are cooler. Other white (warmest in the scene)
objects that are common are roads and pavement that retain latent heat
from sunshine during the day, man hole covers, street lights, house
lights, fires, furnace stacks on houses, car engines that are running
or have run recently, groundwater seepages, puddles, ponds, streams,
rivers and large rocks and boulders in the woods. Other animals in the
picture are often white or bright. Domestic animals are commonly very
bright - hotter than deer, which have highly insulating coats.
In order to count deer with a high degree of confidence and accuracy,
several factors have to be taken into account. Among them are deer infrared
signatures, background infrared signatures, deer behavior and location.
Questions we are commonly asked and the answers given include the following:
How do you know you are not counting the same deer twice?
Given:
- deer are not disturbed by a light plane flying more than a quarter
of a mile above them,
- deer often congregate in groups of two or more - up to 20 or more
in extreme cases,
- deer generally move very slowly as they graze, congregate or rest,
- deer live and act according to generally well known behaviors,
- we fly along a well documented flight path with an ‘infrared
view’ of a known area below the aircraft that is recorded on
videotape.
With the help of a mapping program, we can place dots representing deer
on a map in their respective positions and orientation to one another
quite accurately, particularly when referring to the nearby streets,
intersections, rivers and streams that may be in view or recently in
view on the videotape. As we analyze the tape, becoming quite familiar
with the ‘neighborhood’ of the count area (houses, roads,
hills, streams, rivers, golf courses, trails, etc.) and place the dots
on the map, we recognize specific deer and groups of deer as we pass
them a second and sometimes third time. For example, we may see and
place a group of three deer/dots in an equilateral triangle near a trail
a few seconds after passing a particular road. In the case where we
first saw them they may have been on the right side of the screen. When
we fly the next adjacent run, thanks to overlapping imagery, they may
appear on the extreme left side of the screen. Very often, they will
be in the same spot or not far from it, in the same or similar ‘formation’
five, ten, fifteen or even thirty minutes later. If we fly along and
see a lone deer in the forest, it will still be there in the same general
area when we make adjacent passes. On occasion, we will fly over a group
of deer in an area, and on subsequent passes, we will see an additional
deer that we did not see earlier because it may have been out of the
picture, too close to another deer (appearing larger than normal - but
not counted as two) or it may have been obscured by a tree or foliage
on the first pass. In those cases, we add the dot to the map. In uncommon
cases where deer are moving quickly, we will look for them elsewhere
in the direction they were originally seen moving. If we later see deer
in the vicinity and cannot recognize them as the same group, we have
to make a judgment whether to count them or not.
How do you know what you are seeing and counting are deer, not
some other animal?
Given:
- there is usually a sizable quantity of deer in the area in which
we are flying the deer count,
- there are other wild and domestic animals in the same area, usually
in smaller numbers,
- deer don’t climb trees,
- deer are somewhat ‘brazen’ in their occupation of human
communities, domesticated animals are often corralled, fenced in,
densely grouped or tethered,
- deer are notably larger than foxes, raccoons, skunks and many dogs
and smaller than cows and horses,
- deer have a variety of apparent temperature ranges/thermal signatures
but are nearly always cooler than common domestic animals (dogs, horses,
cattle, sheep),
- skunks, raccoons, and foxes appear to have warmer apparent body
temperatures than deer and often look like a bright pinpoint of light
in the woods, whereas a deer is larger, usually cooler and with less
distinguishable edge contrast with their surroundings (i.e., they
look slightly ‘fuzzy’ around the edges).
- deer congregate more and move less, and generally less rapidly,
than smaller nocturnally active wild animals such as skunks, raccoons,
coyotes and foxes.
Experience, practice and experiments counting and identifying a variety
of captive animal types have given us high confidence in identifying
deer in their normal forest, rural and suburban habitats. The deer that
we have difficulty identifying and counting are those that are partially
hidden from view in evergreen vegetation or exhibit such a low apparent
temperature (thermal signature) that we cannot see them or distinguish
them sufficiently enough to identify them as deer, or even as animals.
We do not count ‘white dots or blobs’ that we do not have
a strong feeling are deer. This includes deer bedding areas in light
snow cover that contain melted through areas to the ground that approximate
deer thermal signatures. Close examination of most infrared deer count
videotapes will reveal to the viewer quite a few animals in trees or
on the ground that do not appear on the deer count map. These animals
are most likely to be something other than deer. Our deer counts are
generally considered a minimum definite number - as opposed to a maximum,
possible number. Some deer will go undetected in nearly every environment.
How accurate is the count?
We don’t know, but believe an average of 90% is in the ballpark,
perhaps better, sometimes worse. Conventional methods (deer-car collisions,
spotlighting, pellet counts, deer tracks) are considered to be accurate
within 30 to 40 percent - not a high number. In this method, we are
looking at 100% of the area in question and under good conditions all
active deer not hidden from view should be seen and counted with infrared.
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