Field Notes Three

Observing Tornado Aftermath

Introduction

Natural disasters are happening all across the country and UAS applications have been used in order to analyze the aftermath.  We are currently in the peak season for tornados to occur.  In this lab we drove out to a Purdue barn that was recently torn apart by a tornado.  We used the unfortunate circumstances as an opportunity to map out the barn remnants to find out the path taken by the tornado.

Study Area

As mentioned earlier, we drove to a barn located north of Purdue Agriculture fields.  We used two different platforms to collect data.  One being the Mavic 2 Pro and the other being the H520.  Flight characteristics are an altitude of 61m while flying with the camera angled nadir.  The flight took place on 05/29/19 during the time of 11:10 am to 12:30 pm.   The weather being partly cloudy accompanied with calm winds had a temperature of 70 degrees Fahrenheit.  

Methods

This mission did not include any Propeller aeropoint GCPs.  We began with flying the Mavic in video mode.  This was intended to get a view of the area that we going to be surveying.  After we recorded a video of the line of barn debris, we put the camera angle to nadir and manually took photos along the line of debris.  The H520 was then used with a programmed mission in order to take photos of the debris.  These flights both took approximately 20 mins.  After mapping the line of debris, the H520 had a mission planned to map the area around the barn's foundation.  This flight had to be cut short due to the construction crew coming back from their lunch break.

Discussion

Below is an image of the overlap of the processed images from the Mavic 2 Pro platform.

As you can see from the image, there is a large lack in overlap of the field.  This could be attributed to the fact that the Mavic flight was the only one to be performed in manual flight.  Manual flight is difficult to get proper overlay and consistent flight paths to get a solid orthomosaic.

Above is the completed mosaic by the Mavic.  As you can see, the completed product does not look very professional and the detail of the debris is not worth showing due to its lack in quality.

Below is an image of the orthomosaic taken by the H520 with the E-90 sensor.

Unlike the Mavic flight, this mission was planned in the H520 transmitter prior to flight.  The mosaic turned out great and had quality details of the debris spread over the field.  The H520 did an excellent job of getting overlapping images due to the large flight plan.  This type of data collection is preferred over manual flight because it is able to cover larger areas more accurately.

Conclusion

Analyzing results from natural disasters with UAS applications has emerged over the years proving incredibly useful data.  Using a UAS for this is safer and easier.  With our mission, we were able to determine the general flight path from the tornado and where the debris landed throughout the field.  An important takeaway from this mission is that planned missions are almost always preferred over manual missions as seen with the comparison between the Mavic and H520 flights.