Getting Started with UAV Imaging Systems: A Radiometric Guide
This SPIE Press Book excerpt focuses on UAV imaging platforms.
Unmanned aerial vehicles (UAVs) will revolutionize the ways in which we conduct business, perform research, enforce the law, manage natural resources, educate students, and execute many other tasks. While advances in computing technology enhance cloud storage and maximize data exploitation, the UAV imaging sensor remains the key component driving system performance and market growth.
This book, Getting Started with UAV Imaging Systems: A Radiometric Guide, is an effort to examine UAV imaging systems in light of their platform and applications contexts.
The following excerpt from Chapter 5 focuses on platforms as prelude to examining how mission requirements are met using commercial cameras in different regions of the electromagnetic spectrum.
The larger platforms' imaging sensors are well-defined; rather than developing new sensors for each mission, sensor suites for theater and tactical U. S. DoD platforms are specified long in advance. Table 5.2 lists mission and payload types on some larger platforms. Several carry both video and still cameras and include laser instrumentation for covert target illumination.1
While different UAV systems have been designed for different missions and/or altitudes/durations, there is some competition for instruments within the DoD. For example, sensors from the manned U2 reconnaissance platform have been integrated into Global Hawk with the goal of long-term cost savings.3
Small UAV platforms and their imaging sensors serve both military and commercial markets. Increasingly, the term "sUAS" appears to distinguish this type of platform/sensor and associated ground-control hardware from its heavier cousins.4 The Raven, for example, is noteworthy in this category. "SWaP-C," where "C" stands for cost, expresses the importance of minimizing the size, weight, power and cost constraints while meeting mission requirements. Manufacturers advertise their sensors as "low SWaP" or even "smallest SWaP."5 Table 5.3 lists some of the factors that contribute to the design of low SWaP-C systems.
The extreme example of "small" is a swarm configuration, whereby numerous small platforms carrying miniature cameras are connected via a communications network.9 More specifically, the term refers to the ability of a collection of small UAVs to achieve a specific objective. The technologies necessary for a successful swarm mission include those in Table 5.3; artificial intelligence (AI) also contributes.10 Miniaturized hardware and enhanced networking capability are key to this strategy's success, which furthers the disruptive effects of UAV imaging. Very small drones that fit in the palm of one's hand are already commercially available.11
The choice of a UAV platform for a smaller sensor is not typically performed according to one, uniform set of criteria. Often, the platform integrator will choose a sensor that best suits a customer's application (one reason it behooves sensor manufacturers to work closely with platform developers.) Contributing factors in platform selection include cost and deployment strategy. For example, situations that involve limited space for maneuvering (such as dense forests) benefit from a rotary aircraft for vertical takeoff and landing.12 Table 5.4 lists some of the factors that influence platform selection.
Many other factors are relevant for specific applications, including the ability of the platform to fit a specific carrying case or transport backpack. Integrating UAV sensors to their platforms is an art in its infancy and will develop as the industry matures.
1. Traditionally, military cameras operating in the visible portion of spectrum are called "EO." Therefore, one often sees the term "EO/IR" sensors to refer to visible and infrared cameras, respectively.
2. Catapulted from a rail launcher, see p. 43 in Gertler1.
3. Malenic, Marina, "Northrop Grumman to test U2 Sensors on Global Hawk," Internet Archive (IHS Jane's Defence Weekly), https://web.archive.org/web/20150502152529/http://www.janes.com/article/51076/northrop-grumman-to-test-u-2-sensors-on-global-hawk, Retrieved 4/5/2017.
4. The distinction between sUAS and sUAV may confuse some readers. The first acronym includes the supporting hardware and/or software used for control.
5. Sensors Unlimited-UTC Aerospace Systems, "SWIR Camera for UAVs," Photonics Online, http://www.photonicsonline.com/doc/swir-camera-for-uavs-0001 Retrieved 5/23/15.
6. Sofradir-EC, "Uncooled infrared detectors achieve new performance levels and cost targets," Sofradir-EC White Papers, http://www.sofradir-ec.com/wp-uncooled-detectors-achieve.asp Retrieved 5/23/15.
7. "Lensless Smart Sensor Technology is SWaP-C Friendly," The Rambus Blog, http://www.rambusblog.com/2015/01/26/lensless-smart-sensor-technology-is-swap-c-friendly/ Retrieved 5/23/15.
8. J. Child, "Small UAV payloads wrestle with SWaP Challenges," COTS Journal, October, 2008, http://archive.cotsjournalonline.com/articles/view/100869 Retrieved 5/23/15.
9. See p. 15 in Gertler1.
10. This author's opinion.
11. H. Timmons, "A swarm of incredibly cheap camera drones is buzzing your way," Quartz, 1/14/15, http://qz.com/326264/a-swarm-of-incredibly-cheap-camera-drones-is-buzzing-your-way/ Retrieved 10/6/15.
12. C. VanVeen, Headwall Photonics, communication to author 5/29/15.
-Barbara G. Grant, SPIE Senior Member and UC-Irvine Division of Continuing Education Distinguished Instructor, received a MS in Optical Sciences from the University of Arizona in 1989, where she did her graduate research work in the Remote Sensing Group, concentrating on the radiometric calibration of imagers including those on the Landsat Thematic Mapper, SPOT HRV, and the NOAA AVHRR.
She worked at Lockheed-Martin and for NASA-Goddard contractors addressing radiometric calibration in the visible, near-infrared, and thermal infrared, and overseeing the integration and test of the GOES-8 and -9 imager and sounder, for which she received two NASA awards.
Her previous books for SPIE Press include The Art of Radiometry, which she completed for the late Dr. Jim Palmer, and Field Guide to Radiometry.
In 2016, she formed Grant Drone Solutions, LLC, to take the concepts behind the current book into practical application within the emerging UAV marketplace.