AT409 Week 3 Report

 

Figure 1:DJI M600 Being Prepared for Flight

 

Introduction:

This week our flights continued at the Martell forest area. Our flight crew was assigned to fly the first of 4 missions over a specific plot of trees for one of the PHD students in the Purdue forestry department. This week I was assigned the role of pilot in command (PIC) and given responsibility of the first flight which allowed me to have a more hands on experience with crew resource management (CRM), checklists and flying the mission than I’ve had previously: all of which I will go into more detail with below.  Additionally, this was our flight crews’ first experience handling and recording information from ground control points (GCPs). And our mission this week involved general handling and placement of the GCPs, their operational use, as well as a small experiment that was more for our benefit of learning what not to do rather than gathering useful data. 

 

Overview:

Figure 2:AeroPoint Ground Control Point Unit

Mission Prep and GCPs

Once we arrived at the mission area and had our usual brief on the mission and crew assignments, we began to set up our GCPs. For this mission we used 10 AeroPoint GCP platforms as seen in figure 2 above. We then set about placing ad turning on our GCPs. We placed most of our GCPs around the perimeter of the mission area and a few in the forest itself under the canopy. Its important to note at this point the importance of GPS “soak” time. Without being too technical, “soak” time refers to the amount of time the GCP needs to acquire the appropriate amount of satellites and calibrate its position after it is turned on and before the flight takes place. What this means for us as a flight crew is that we had to mark the time that we activated our first GCP, and make sure that our flight didn’t commence until our GCPs had “soaked” for a minimum of 45mins as per the recommendation by AeroPoint. 

I’ve talked at length about GCPs in previous writings before, but for a refresher; a GCP is basically a GPS transceiver that uses satellites to acquire precise data on its location on the Earth’s surface. It then interfaces with our drones to provide accurate, real-time positional data which allows the drone and the sensors on it to create the precise image data with correct positioning for our GIS work. With this in mind we come to a unique problem we had for this mission; GCPs need an un interrupted line of sight (LOS) to the satellites they are connecting to in order to generate accurate positional data (as pointed out in figure 3 below). And, seeing as our mission was taking place over a plantation of densely planted trees, we were going to have problems finding suitable locations to place our GCPs. This is where we had a bit of an experiment for our learning benefit as we deliberately place some of our GCPs under the forest canopy where it was very unlikely to get accurate data from the satellites. This had the affect of when we went to post process the image data, we could only find one of the four GCPS we had planed under the forest canopy which rendered some the images we collected unusable.

Figure 3:AeroPoint GCP Instructions

As GCPs are an essential part of creating using GIS datasets and many things go into their placement and usage. For example, our GCPs needed to have good coverage over the area we are surveying. This means they need to be fairly evenly spaced out over the width, length, and breath of the area. If the GCPs are too clustered in one area our eventual data when we generate a combined image or 3D map will look like its being stretched or warped to the area with the high concentration of GCPs. 

Flight Ops.

With our GCPs set up and soaked we were ready to begin flight preparations. As PIC for the first flight I was responsible for leading my flight crew through the preflight checklist, I talked at length about checklists in last weeks report so I’ll be brief with this; once we established out flight line we began to assemble the aircraft, I was responsible for checking my fight crew as they did this though there were many nuances that my TA Zach had to coach me through. Which is a good time to iterate that the checklist is not meant to be a finely detailed document, but rather a quick reference for a user already familiar with the system and checklists are NOT an alternative for proper training on a system. There are many things that contribute to smooth and efficient preparation of the aircraft and sensors for flight that are not on the checklist, such as how to arrange the boxes when you have retrieved their contents or where to store the lenses covers for the sensors to where you don’t lose them or walk off at the end of the mission with them still in your pocket and this mission as PIC was a good experience for that.

Once the aircraft was assembled I began to plan the flight with the Pix4D system, normally the PIC would either do this prior to arriving on site or concurrently with the aircraft assembly and preflight checklist but being as this was my first experience operating the DJI M600 platform this was essentially a training flight for me and my TA wanted me to focus on each step individually. The Pix4D system is very intuitive and it took very little time for me to upload the flight plan to the aircraft. And once the checklist was completed, we began our first flight. Our group originally planned to fly 5 flights that day from 500-100ft AGL, but time constraints meant that our last 2 flights had to be postponed. The metadata for the 3 flights we completed are recorded below.

Metadata:

*Sensor angle, overlap, sidelap, and dataset are shared across all flights. And GCP start time was the same for all flights

General:

Location	Martell Forest
Date	9/8/2020
Vehicle	DJI M600
Sensor	Sony A6000
GCP	AeroPoint
Number of GCPs	10

 

Flight 1:

Takeoff Time	11:16 AM
Landing Time	11:23 AM
Altitude (ft)	500
Sensor Angle	NADIR
Overlap	80%
Sidelap	80%
Dataset	1
Airtime	7 min
GCP start time	9:47 am
Crew
PIC	John Cox
FO	Jeff Hines
SO	Logan Jones
VO	Zach Miller

 

Flight 2:

Takeoff Time	12:08 AM
Landing Time	12:15 AM
Altitude (ft)	400
Crew
PIC	Aaron Barnau
FO	Tresten Russell
SO	Tristen Bungen
VO	Zach Miller

 

Flight 3:

Takeoff Time	12:37 Am
Landing Time	12:45 AM
Altitude (ft)	300
Crew
PIC	Logan Jones
FO	Connor Cromwell
SO	Joe Hammel
VO	Zach Miller

 

Data Processing:

After our flight was completed my flight crew was instructed to go back to our computer lab and unpack our equipment and learn how we will be post processing our data this semester. Once Zach arrived with the equipment, we started recharging the batteries as they could charge while we did other things, then Zach showed us how to download the data from the GCPs using our phone. After that we recovered the sim cards from the aircraft sensors and began to upload the data to our University research drive, we were also instructed in the correct was to catalog data in the research drive as well as how to format the data and the cards for the next flight. Our data consisted of both RGB and thermal image data, which had to be separated, as well as separated by flight in order for the data to be compared later on. While this all may sound trivial, this is essential for efficient and organized operation, all of our data goes into an initial data collection folder in the research drive, while all work is done in a separate processing folder, and deliverables and completed projects are stored in an analysis folder. This is done so that anyone in our group can easily find the data we’re looking for as we may have multiple different flight crews over many days or weeks gathering data for a project before it is processed into a final product and its important that any of our members be able to quickly find and access the data they require.

Summary:

GCPs are a vital part of UAS/GIS operations and the operational use of them is not a procedure to be taken lightly. There are unique challenges that arise when using GCPs or UAS operations and care must be taken in GCP placement and handling.

Preflight checklists are not training manuals, or material used for learning how to operate a system, a UAS operator should know the ins and outs of their system before any operation.