Interview with Alison Ballance, Radio National New Zealand - click on the link below...
Labels: AUT Fox, Data collection, NIR camera, Pix4UAV, Skycam, Swampfox, vegetation stress camera
We are now making significant progress with our bush survey and ground truthing. However, each step forward has the potential to raise new problems, some obvious, but others requiring a bit of detective work.
A few weeks ago, we went back to our piece of bush near to the North Shore Model Aero Club strip and flew several transects with our vegetation stress camera. We launched in a 15-20kph wind (as a full-scale pilot I have real difficulty thinking in terms of kph and not knots!) and began the survey, but the aircraft reported wind of up to 30kph. This caused our transects to be 'bent' - the autopilot attempts to arrive at the waypoint, but in a cross wind, the track becomes significantly curved. No problem for the aircraft, but the images must overlap significantly for us to use Pix4UAV to synthesise the orthomosaic.
We decided to bring the aircraft back overhead the GCS and commenced a manual approach, using the GCS computer to bring the A/C down in 50ft increments and the hand controller to steer the Hawk. (Our trainer suggested that manual steering and a lower parachute deployment is a better option than a full auto approach in stronger conditions). In Heading Manual mode, the autopilot maintains airspeed and stabilises the A/C. It appears that shortly after entering Heading Manual mode, the pilot engaged Partial Control mode. This allows the pilot to control both roll and pitch, and airspeed. No problem here - the pilot is an accomplished model aircraft flyer. At an appropriate height the pilot cut the throttle and deployed the recovery parachute. The chute deployed properly and the A/C began its descent. However, close to the ground there was significant turbulence and the A/C began to pitch and roll violently. It landed safely, but the parachute began to drag, cartwheeling the A/C over the rough ground, breaking the main spar and one elevator, and damaging the vertical stabiliser. All this can (and has been ) fixed.
When we analysed the images from the vegetation stress camera, we found that we had more images than were recorded in the photo log file. This is a potential problem, as the images must be geo-referenced for entry into and processing by Pix4UAV.
A quick chat with Dr. Tim Brooks at Skycam revealed something more that we didn't know - when the aircraft is put into Partial Control mode, the camera can continue photographing, but the images are not recorded in the photo log. Problem solved - just match the photographs to the point in the photo log where the last image was recorded and discard the rest.
Our student, Hins, processed the images and we find that we collected a good set, but that there is a strip down the middle of the bush with no images; the result of the curved transects. One solution is to enter intermediate waypoints into the flight path to force the A/C to fly straighter transects.
Major lessons learned: when the aircraft is landing under parachute, the ground team need to get to the touchdown point quickly to secure the aircraft, and when the wind is up around 15 - 20kph and forecast to rise, it's probably better to stay in the UAV Ops HQ and write papers, or if desperate for a flying fix, practice with the flight simulator!
A few weeks ago, we went back to our piece of bush near to the North Shore Model Aero Club strip and flew several transects with our vegetation stress camera. We launched in a 15-20kph wind (as a full-scale pilot I have real difficulty thinking in terms of kph and not knots!) and began the survey, but the aircraft reported wind of up to 30kph. This caused our transects to be 'bent' - the autopilot attempts to arrive at the waypoint, but in a cross wind, the track becomes significantly curved. No problem for the aircraft, but the images must overlap significantly for us to use Pix4UAV to synthesise the orthomosaic.
We decided to bring the aircraft back overhead the GCS and commenced a manual approach, using the GCS computer to bring the A/C down in 50ft increments and the hand controller to steer the Hawk. (Our trainer suggested that manual steering and a lower parachute deployment is a better option than a full auto approach in stronger conditions). In Heading Manual mode, the autopilot maintains airspeed and stabilises the A/C. It appears that shortly after entering Heading Manual mode, the pilot engaged Partial Control mode. This allows the pilot to control both roll and pitch, and airspeed. No problem here - the pilot is an accomplished model aircraft flyer. At an appropriate height the pilot cut the throttle and deployed the recovery parachute. The chute deployed properly and the A/C began its descent. However, close to the ground there was significant turbulence and the A/C began to pitch and roll violently. It landed safely, but the parachute began to drag, cartwheeling the A/C over the rough ground, breaking the main spar and one elevator, and damaging the vertical stabiliser. All this can (and has been ) fixed.
When we analysed the images from the vegetation stress camera, we found that we had more images than were recorded in the photo log file. This is a potential problem, as the images must be geo-referenced for entry into and processing by Pix4UAV.
A quick chat with Dr. Tim Brooks at Skycam revealed something more that we didn't know - when the aircraft is put into Partial Control mode, the camera can continue photographing, but the images are not recorded in the photo log. Problem solved - just match the photographs to the point in the photo log where the last image was recorded and discard the rest.
Our student, Hins, processed the images and we find that we collected a good set, but that there is a strip down the middle of the bush with no images; the result of the curved transects. One solution is to enter intermediate waypoints into the flight path to force the A/C to fly straighter transects.
Major lessons learned: when the aircraft is landing under parachute, the ground team need to get to the touchdown point quickly to secure the aircraft, and when the wind is up around 15 - 20kph and forecast to rise, it's probably better to stay in the UAV Ops HQ and write papers, or if desperate for a flying fix, practice with the flight simulator!
Labels: AUT Hawk, Pix4UAV, vegetation stress camera
Up to now, we have had a very good run of data collection and training. Last sortie, there was a bit of a scare when the Hawk landed in a clearing close to some large trees. This week our good run ended.
We launched the Hawk, carrying our newly modified vegetation stress camera, into a 15kph wind. During the flight, the wind got up a bit and the telemetry indicated a wind speed of about 30kph at 400ft AGL. However, this was quite smooth air with little turbulence.
We conducted a number of transects of our study area, hoping to collect data on the vegetation that we could compare with our spectroradiometer ground truthing. We sent the students off into the bush to collect reflectance readings, while the UAV Team flew the sortie.
When we calculated that we had almost filled the camera data card with images, we recalled the Hawk. She dutifully returned to overfly the GCS. This was the point where things began to go wrong.
The Operator entered another two waypoints and turned the camera on again to collect a short transect over the GCS. We had a blue tarpaulin laid out on the ground and we hoped to get an indication of resolution from 400ft AGL. When this transect was finished, the Operator entered L4, the command for an automated parachute landing. However, none of us realised that the Hawk would now attempt an automated approach to the last waypoint, rather than the take-off point. (We now understand that we should have entered L4 while in Return mode).
The aircraft performed a series of circles with decreasing height about 200 metres to the East of our GCS position. Expecting the parachute to deploy upwind of the GCS we were startled to see it pop out 200m to the East. In the strong wind, the Hawk drifted gently but inexorably towards the trees. The more optimistic of us thought it would land just to the West of the trees, but the parachute caught right at the end of the tallest branch about 60ft AGL.
Since we were flying from a model aircraft field, Dr. John R. knew that this was not an uncommon occurrence and telephoned a tree removal company. They arrived within about 90 minutes and recovered the Hawk. Unfortunately, the tree climber either didn't tie a good knot to the Hawk, or completely forgot, because as the branches were cut away, the aircraft crashed to the ground from about 40ft, landing on the starboard wing and breaking the tip off.
So... we are grounded until repairs can be carried out. Our trusty suppliers, Skycam UAV, analysed the flight log today and determined what we had done wrongly. They believe that the wing can be repaired and today I packed the whole aircraft into its transport Pelican case and sent it to Skycam UAV by courier.
The one saving grace is that we collected approximately 270 images with the vegetation stress camera.
Several important lessons learned - proper operation of the landing procedures, emergency recovery to normal flight, alternative landing methods, and perhaps the most important of all: full communication between the Operator, Mission Commander and observers.
We launched the Hawk, carrying our newly modified vegetation stress camera, into a 15kph wind. During the flight, the wind got up a bit and the telemetry indicated a wind speed of about 30kph at 400ft AGL. However, this was quite smooth air with little turbulence.
We conducted a number of transects of our study area, hoping to collect data on the vegetation that we could compare with our spectroradiometer ground truthing. We sent the students off into the bush to collect reflectance readings, while the UAV Team flew the sortie.
When we calculated that we had almost filled the camera data card with images, we recalled the Hawk. She dutifully returned to overfly the GCS. This was the point where things began to go wrong.
The Operator entered another two waypoints and turned the camera on again to collect a short transect over the GCS. We had a blue tarpaulin laid out on the ground and we hoped to get an indication of resolution from 400ft AGL. When this transect was finished, the Operator entered L4, the command for an automated parachute landing. However, none of us realised that the Hawk would now attempt an automated approach to the last waypoint, rather than the take-off point. (We now understand that we should have entered L4 while in Return mode).
The aircraft performed a series of circles with decreasing height about 200 metres to the East of our GCS position. Expecting the parachute to deploy upwind of the GCS we were startled to see it pop out 200m to the East. In the strong wind, the Hawk drifted gently but inexorably towards the trees. The more optimistic of us thought it would land just to the West of the trees, but the parachute caught right at the end of the tallest branch about 60ft AGL.
There's always someone with a camera to record your misfortunes!
The AUT Hawk, apparently nesting in a pine tree
So... we are grounded until repairs can be carried out. Our trusty suppliers, Skycam UAV, analysed the flight log today and determined what we had done wrongly. They believe that the wing can be repaired and today I packed the whole aircraft into its transport Pelican case and sent it to Skycam UAV by courier.
The one saving grace is that we collected approximately 270 images with the vegetation stress camera.
Several important lessons learned - proper operation of the landing procedures, emergency recovery to normal flight, alternative landing methods, and perhaps the most important of all: full communication between the Operator, Mission Commander and observers.
Labels: AUT Hawk, CofG, spectroradiometer, UAV, vegetation stress camera