Headwall Photonics Blog

Smaller, Lighter, Better: Hyperspectral on UAVs

Posted by Christopher Van Veen on Fri, Aug 08, 2014

At Headwall we've been busy listening to the market. When it comes to airborne remote sensing, the market is telling us that they favor UAVs (unmanned aerial vehicles) of all kinds: fixed-wing, multi-rotor, and so on. There's no end to the number of companies producing UAVs globally. Because many UAVs produced today are very small and affordable they are 'within reach' of those with even modest means. Universities represent one key market where the use of UAVs is rapidly increasing. Full of scientists and research departments, universities around the globe see these small and light UAVs as a perfect platform from which to launch their exploratory studies. They are affordable, easy to assembly and transport, and (especially with multi-rotor models) can take off and land within a very small footprint.

UAV with NanoBut alongside all this enthusiasm for UAVs, there are many who frown upon these airborne vehicles and see them as a nuisance. Indeed, they can be a nuisance when used for trivial pursuits. In densely-populated areas they certainly can be more than an annoyance...they can be dangerous. But largely, the work we are seeing our customers undertake with hyperspectral imagers attached to UAVs is very valuable work indeed. And it takes place far from the hustle and bustle of any urban landscape. For example, precision agriculture is made more valuable because there are key indices to plant health and physiology that are readily seen from above than from below. Certain disease conditions are ‘visible’ using hyperspectral imaging, especially with high spectral and spatial resolution found on all Headwall sensors.  Other research pursuits include environmental analysis, geology, pollution analysis, and so many more. These are very good and valuable scientific efforts made moreso by the UAVs that enable these precision instruments to 'fly.' The marriage between hyperspectral and UAV seems to be a perfect one, especially when you consider how much ground can be covered with one of these flying wizards. And especially when you realize that hyperspectral imaging fundamentally requires that movement needs to occur. In other words, hyperspectral was meant for airborne deployment. Where a Jeep can’t go, a UAV can. And furthermore, more ground can be covered with a UAV, meaning more efficient data collection over rugged and inaccessible landscapes.

Nano-HyperspecAs UAVs get smaller and lighter, users run headlong into the issue of payload: UAVs are limited with respect to what they can lift. Whatever else a UAV is asked to carry, it needs to lift batteries. Then comes the instrumentation. Headwall’s Nano-Hyperspec was just introduced for the VNIR (400-1000nm) spectral range. Most (but not all) of the things a research scientist might wish to ‘see’ are visible in this spectral range. But we did a couple things with Nano-Hyperspec that helps the payload issue. First, the size and weight are well below previous sensor offerings. Its size (including lens) is a scant 3” x 3” x 4.72” (76.2mm x 76.2mm x 119.2mm), and its weight is less that 1.5 lb. (0.68kg). Best of all, this includes on-board data storage of 480GB. That’s about 130 minutes at 100fps.

Aside from making Nano-Hyperspec smaller and lighter than other hyperspectral sensors, a key differentiator comes from embedding the data storage within the enclosure while providing multiple attach points for the GPS/INU. Another key attribute is the inclusion of the full airborne version of Headwall’s Hyperspec III software, which includes a polygon flight tool for sensor operation and a real-time Ethernet Waterfall display. While the work to shrink the size and weight of Nano-Hyperspec is valuable by itself, it does allow the user more room and available payload to carry other instrumentation. Hyperspectral combined with LiDAR and thermal imaging is an extremely valuable package that is made possible thanks to the overall size/weight reduction of Nano-Hyperspec and the embedding of the data storage/management capabilities (which were contained within a separate enclosure previously).

Hyperspec III software gives users full control over data acquisition, sensor operation, and datacube creation in ENVI-compatible format. Hyperspec III also works in full conjunction with the GPS that can be paired with the sensor as an available Airborne Package. In this optional package, customers are able to take advantage of real-time computation of inertial enhanced position/velocity, ~161dBm tracking sensitivity, accurate 360-degree #D orientation output of attitude and heading, correlation of image data to GPS data, and much more. During post-processing, the Airborne Package also effortlessly handles radiometric calibration and conversion as well as orthorectification.



Tags: Airborne, Remote Sensing, UAV, agriculture, precision agriculture