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Monocular Vision System for Fixed Altitude Flight of Unmanned Aerial Vehicles.

Huang KL, Chiu CC, Chiu SY, Teng YJ, Hao SS - Sensors (Basel) (2015)

Bottom Line: The UAV flight system can be set to fly at a fixed and relatively low altitude to obtain the same resolution of ground images.A forward-looking camera is mounted on the upside of the aircraft's nose.Experimental results show that the proposed system enables UAVs to obtain terrain images at constant resolution, and to detect the relative altitude along the flight path.

View Article: PubMed Central - PubMed

Affiliation: Department of Electrical and Electronic Engineering, Chung Cheng Institute of Technology, National Defense University, Taoyuan 33551, Taiwan. 1040510304@ndu.edu.tw.

ABSTRACT
The fastest and most economical method of acquiring terrain images is aerial photography. The use of unmanned aerial vehicles (UAVs) has been investigated for this task. However, UAVs present a range of challenges such as flight altitude maintenance. This paper reports a method that combines skyline detection with a stereo vision algorithm to enable the flight altitude of UAVs to be maintained. A monocular camera is mounted on the downside of the aircraft's nose to collect continuous ground images, and the relative altitude is obtained via a stereo vision algorithm from the velocity of the UAV. Image detection is used to obtain terrain images, and to measure the relative altitude from the ground to the UAV. The UAV flight system can be set to fly at a fixed and relatively low altitude to obtain the same resolution of ground images. A forward-looking camera is mounted on the upside of the aircraft's nose. In combination with the skyline detection algorithm, this helps the aircraft to maintain a stable flight pattern. Experimental results show that the proposed system enables UAVs to obtain terrain images at constant resolution, and to detect the relative altitude along the flight path.

No MeSH data available.


Relative altitude calculation with a single camera.
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sensors-15-16848-f005: Relative altitude calculation with a single camera.

Mentions: After the flight direction has been determined, changes in direction caused by wind can be detected. Hence, the direction of the baseline can be detected from the flying direction. When the length of the baseline is estimated, the altitude between the UAV and the ground can be calculated. Figure 5 illustrates how monocular vision-based altitude measurement is carried out for UAVs. The forward-looking camera captures images that are then processed by the skyline detection algorithm to maintain aircraft stability. The downward-looking camera captures two consecutive images that are processed by the stereo vision algorithm to obtain the relative distance between the airplane and ground. Wang et al. [16] and Song et al. [11] calculated the altitude information using two cameras. In this study, only one camera is used to detect the relative altitude. Assume that a reference point P is located on the ground. Figure 5 illustrates the detection of the altitude between the aircraft and P. Assume the length of the baseline b is as shown in Figure 5, and that the parameter f is the focal length of each camera. Cil and Cir are the centers of consecutive images. The reference point P is projected to the consecutive images to give Pl and Pr, respectively. Along the direction of the baseline, assume the projection value of is Δdl and the projection value of is Δdr. The parameter Wpixel is the width in pixels of the image sensor, and the parameter H is the distance between the center point of the baseline and P.


Monocular Vision System for Fixed Altitude Flight of Unmanned Aerial Vehicles.

Huang KL, Chiu CC, Chiu SY, Teng YJ, Hao SS - Sensors (Basel) (2015)

Relative altitude calculation with a single camera.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4541911&req=5

sensors-15-16848-f005: Relative altitude calculation with a single camera.
Mentions: After the flight direction has been determined, changes in direction caused by wind can be detected. Hence, the direction of the baseline can be detected from the flying direction. When the length of the baseline is estimated, the altitude between the UAV and the ground can be calculated. Figure 5 illustrates how monocular vision-based altitude measurement is carried out for UAVs. The forward-looking camera captures images that are then processed by the skyline detection algorithm to maintain aircraft stability. The downward-looking camera captures two consecutive images that are processed by the stereo vision algorithm to obtain the relative distance between the airplane and ground. Wang et al. [16] and Song et al. [11] calculated the altitude information using two cameras. In this study, only one camera is used to detect the relative altitude. Assume that a reference point P is located on the ground. Figure 5 illustrates the detection of the altitude between the aircraft and P. Assume the length of the baseline b is as shown in Figure 5, and that the parameter f is the focal length of each camera. Cil and Cir are the centers of consecutive images. The reference point P is projected to the consecutive images to give Pl and Pr, respectively. Along the direction of the baseline, assume the projection value of is Δdl and the projection value of is Δdr. The parameter Wpixel is the width in pixels of the image sensor, and the parameter H is the distance between the center point of the baseline and P.

Bottom Line: The UAV flight system can be set to fly at a fixed and relatively low altitude to obtain the same resolution of ground images.A forward-looking camera is mounted on the upside of the aircraft's nose.Experimental results show that the proposed system enables UAVs to obtain terrain images at constant resolution, and to detect the relative altitude along the flight path.

View Article: PubMed Central - PubMed

Affiliation: Department of Electrical and Electronic Engineering, Chung Cheng Institute of Technology, National Defense University, Taoyuan 33551, Taiwan. 1040510304@ndu.edu.tw.

ABSTRACT
The fastest and most economical method of acquiring terrain images is aerial photography. The use of unmanned aerial vehicles (UAVs) has been investigated for this task. However, UAVs present a range of challenges such as flight altitude maintenance. This paper reports a method that combines skyline detection with a stereo vision algorithm to enable the flight altitude of UAVs to be maintained. A monocular camera is mounted on the downside of the aircraft's nose to collect continuous ground images, and the relative altitude is obtained via a stereo vision algorithm from the velocity of the UAV. Image detection is used to obtain terrain images, and to measure the relative altitude from the ground to the UAV. The UAV flight system can be set to fly at a fixed and relatively low altitude to obtain the same resolution of ground images. A forward-looking camera is mounted on the upside of the aircraft's nose. In combination with the skyline detection algorithm, this helps the aircraft to maintain a stable flight pattern. Experimental results show that the proposed system enables UAVs to obtain terrain images at constant resolution, and to detect the relative altitude along the flight path.

No MeSH data available.