or low illumination, including observations during the night.
In Bieszczad
et al.
(2013) and PRlog (2013), small thermal
cameras were designed to be installed onboard
UAVs
with the
aim of carrying out data acquisition in remote sensing opera-
tions under adverse conditions. The spectral bands range
from 8 µm to 12 µm and 7.5 µm to 14 µm, respectively. The
weights of the model proposed in PRlog (2013) depend on the
optical system, being less than 380 g with a lens of 60 mm. Its
size is 57 × 71 × 38.5 mm plus the length of the optical sys-
tem. It contains analog and digital video output interfaces.
Thermal and infrared imagers were identified by Rufino
and Moccia (2005) to be useful for fire detection onboard a
fixed wing vehicle (wingspan 2.75 m and length 1.7 m). The
spectral response band in the thermal camera was 7.5 µm to
13 µm, with a weight less than 120 g. The vehicle was also
equipped with a spectral sensor covering the range of 430 nm
- 900 nm, and a weight of 500 g.
Sheng
et al.
(2010) described the design of a platform with
wingspan of 1,828 mm, weight about 3.7 kg, and equipped
with thermal cameras as a payload. Three thermal cameras
with the spectral band of 7 µm to 14 µm are used, with
weights of 150 g with lens or 108 g and 97 g without lenses.
Analog and digital outputs are allowed.
Lens distortion correction methods were proposed for
improving thermal imaging quality, making thermal systems
more accurate for remote sensing (Yahyanejad
et al.
, 2011).
Bendig
et al.
(2012) equipped an octo-copter (<5 kg and
payload between 0.2 to 1.5 kg) with a thermal sensor (weight
of 300 g) with a mechanical trigger.
Infrared cameras together with visual cameras were used
in Martínez-de-Dios
et al.
(2007 and 2011) for surveillance in
forest fire detection, at times together with ground stations
for image controlling purposes. Figure 4 displays an infrared
camera, onboard the helicopter
HERO
, as part of the sensor sys-
tem on such a platform. Regarding the quality of near-infrared
(
NIR
) images, Ariff
et al.
(2013) reported about the findings of
quality of the captured video from a
NIR
imaging system pro-
totype for night-time surveillance, with potential use in
UAVs
.
UAV
operations have been considered in indoor environ-
ments by using active systems based on infrared sensors. This
is the approach proposed in Lange
et al.
(2012) where the
Kinect
RGB
-
D
sensor is used to obtain dense color and depth
information in an indoor corridor, where the information is
further processed on-board.
Plate 1 displays a thermal image of a field area where each
color represents a different temperature value; red colors
represent higher temperature values and black ones lower
values. The remaining colors represent intermediate values of
temperature.
Scholtz
et al.
(2011) equipped a fixed-wing
UAV
, with a
wingspan of 2 m and take-off weight (
TOW
) of 7 kg includ-
ing 1.5 kg of payload, with an infrared camera (with spectral
range 800 nm - 1200 nm, and weigh = 200 g) and a multispec-
tral camera with 12 channels.
Forward looking infrared (
FLIR
, 2015) systems are adjusted
and developed to be installed onboard
UAVs
with sizes about
22 × 22 × 12 mm and weights up to 28 g with a lens of 35 mm,
including analog and digital video formats.
Kohoutek and Eisenbeiss (2012) used a Time-of-Flight
(ToF) device with 870 nm of illumination wavelength and
weight of 1370 g onboard an unmanned helicopter to obtain
3
D
images representing surface structures.
Emery
et al.
(2014) developed a calibrated radiometer, with
a total weight of 1.36 kg, for infrared measurements of sea
surface temperature from
UAVs
. The sensor is designed with a
2
D
microbolometer array that acquires infrared images in the
8 µm - 12 µm range as the
UAV
flies forward.
Lidar
Light Detection and Ranging (lidar) devices are used to mea-
sure distances by exploring the scene with the light (gener-
ally pulses emitted by a laser) projected on the targets. These
systems have been adapted for
UAVs
, achieving lightweight
systems useful for surveillance or mapping natural and artifi-
cial structures with important improvements. Colomina and
Molina (2014) provided a representative list of laser scanners.
Nagai
et al.
(2004) integrated a laser with a camera onboard a
UAV
for digital surface and feature extraction.
Zhou
et al.
(2012
a
) presented the advance of a premature
flash lidar, including a complete laser emitting system (diode,
conic lens, alignment, divergence angle) and pulse generator
to be installed onboard a
UAV
. Simulated experiments were
conducted and the results reported.
Wallace
et al.
(2012) used a multi-rotor
UAV
(octo-copter)
with maximum payload of 2.8 kg. It is equipped with an Ibeo
LUX laser scanner with maximum range of 200 m and scan-
ning at 12.5 Hz with angular resolutions of 0.25°. The remain-
ing sensors within the payload are an inertial measurement
unit (
IMU
) for positioning and orientation, a dual frequency re-
ceiver
GPS
, a lightweight antenna, and a high-resolution video
camera. This system was also used in Wallace
et al.
(2014
b
).
Plate 1. Thermal image: each color represents a value of tem-
perature (Image courtesy of QuantaLab-
ias
-
csic
, Cordoba, Spain).
286
April 2015
PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING
