Aerospace and Electronic Systems Magazine October 2017 - 49

Changey et al.
sion system was embedded onboard to have a previous validation
in real conditions, before doing the validation on the GLMAV. It
was performed on the time taken by the embedded processor for
compressing a VGA image on the basis of the quality factor Q.
The best quality is for Q = 100, leading to a compression of near
2.6:1; a high quality is for Q = 50, leading to a compression of
about 15:1. A quality factor of 70 was chosen to keep high quality
images and to avoid too high latency. A sequence of images were
recorded onboard the GLMAV on the microSD card and transmitted to the ground station in real time. Figure 20 depicts a raw
image (top) and the two compressed images (bottom) extracted
from the raw one. There is no difference in quality between the
compressed images and the raw image.
Ultimately, the complete observation system is operational and
transmission rates of 7 frames per second to 10 frames per second
of high quality were achieved on distances greater than 500 m.

Figure 17.

Optical prism device.

initialization, the adjustment of various parameters (shutter and
gain), the acquisition of fixed frequency images, the compression
according to JPEG standard and the transmission of the user datagram protocol protocol (Figure 19). The image acquisition and its
compression, the processing, and the WiFi sending constitute three
distinct tasks, which are performed in parallel to minimize latency
and maximize the frequency of images sent to the ground station.
The client runs on the ground station computer connected to
the drone through WiFi, queries the server, sends gain and shutter
instructions, receives the images, performs necessary rotations and
transpositions, and displays the images on the screen or records
them (Figure 19).
The setting of the image compression is a compromise on the
basis of several parameters: desired number of frames per second, WiFi rate available, received image quality, and time taken
by the processor for compression, which introduces a latency.
Tests were performed by using a quadcopter. The complete vi-

CONCLUSION
After 4 years of research and development in the fields of mechanics, ballistics, aerodynamics, electronics, automatics, optics, and
signal transmission, a full prototype of a GLMAV system was designed, manufactured, and tested. The system includes a pyrotechnical dedicated launcher, the GLMAV itself, a ground station, and a
transmission system linked to the ground station. Its development
was relatively long because it was linked to an iterative process
between all fields of research previously mentioned.
The present article is only focused on the electronics and the
vision system with image transmission of the project. The architecture of the embedded electronics allows the real-time control of
the actuators on the basis of the command laws computed by the
onboard processor and the high-level instructions coming from the
ground station and sensor measurements. It can also handle video
acquisition and its transmission to the ground station. For that, all

Figure 18.

Result of a static test (left); vision system, IMU, and transmission elements mounted on the motherboard and integrated in the nose of the final version
2.0 of the GLMAV (right).

OCTOBER 2017

IEEE A&E SYSTEMS MAGAZINE

Table of Contents for the Digital Edition of Aerospace and Electronic Systems Magazine October 2017