The title is intentionally provoking. Too many public comments are similar to “A falling drone will give you a bump on the head”. In fact, there is a reasonable chance it will kill you. Which of these is actually true? We simply do not know and some formal experiments are required before claims are made either way. So my point is not really that they may kill you, rather it is that we need good data.
I’d like to thank the members of a particular Facebook group for engaging in a spirited discussion that helped me refine this post. It was far too provocative in the early draft and I am certain that it still is for some.
The theoretical analysis follows, and it ignores a lot of variables. These calculations are a starting point and represent the “worst case scenario”. With a lot of additional work, we could add other constraints and end up with a probability estimate of damage from a direct impact.
Weight of a DJI Phantom – 1242g (2.73 lbs)
Altitude at time of failure – 61m (200 feet)
Force required to crush a human skull – 2,300N (Journal of Neurosurgery: Pediatrics)
Let’s plug those numbers into a calculator:
7173N of force. Almost three times the force required to crush a human skull.
Even from half that height, 100 feet, a falling Phantom would generate 3527N, still enough to crush your skull. At 65 feet you might survive the impact as the force is down to 2351N.
There are a lot of variables that I did not account for – drag, impact angle, elasticity in the body and the drone…. Real experiments need to be performed.
In an earlier post I wrote: “I think the search & rescue community should do a lot more work on designing and performing experiments with UAVs. Vendors and sales outlets keep touting their UAVs as being “good for search & rescue” without providing any data to support this claim, and often without really understanding SAR, SAR missions, and the challenges we face. (More on this in my upcoming presentation for NAASIC in Reno in September.)”
This is even more important when we consider what are appropriate missions for UAVs and how to deploy them.
I conducted two very quick experiments to illustrate two of the challenges we face. I intend to develop more formal experiments and welcome others who are interested in assisting with this effort.
I wanted to answer two questions:
- How effective is a UAV when searching an area with trees?
- How effective is a UAV when searching for clues in a soybean field?
Both of these are simple examples of SAR problems you can adapt to your own operational area.
tl;dr – You need to be down very low when searching near trees and finding an unresponsive subject in a soybean field with an optical sensor is very tough.
Searching Near Trees:
If this was your search area, and if you were searching for an uncooperative or unresponsive subject (someone who isn’t going to come investigate the noise of the UAV), how would you plan your mission? How would you execute it? How long would it take? How effective would you be? (This was taken at 200 feet by a Phantom Vision 2+. The subject is currently in the frame.)
Ok, if the subject were standing under a tree in this small area, what would you be able to see? (There are a lot of variables here – height of branches, folliage on or off, distance from subject, subject’s distance from the trunk, …. This is just an example.)
Distance from the UAV to the subject was less than 50 feet in all images.
At the subject’s altitude:
At about a 30 degree angle:
50 degrees. The subject’s legs are barely visible due to the contrast between his blue jeans and the green background. (And, if you were looking at this on a mobile device, what would you really be able to see?)
70 degrees or so. The subject is not visible.
Conclusion – you need to get under the level of the tree branches to search around trees for an unresponsive subject. This will increase your time required to search while diminishing your ability to control the UAV at long ranges.
I live, and search, in Illinois. Lots of corn, lots of soybeans. Searching for anyone in a corn field when the corn is above your head is tough. We’ll come back to that one later. Soybeans get to a few feet tall. Walking through soybean fields is … annoying … but you can certainly see a lot more. If the subject is standing up you can just walk to the edge of the field and say “Hey, there they are!” But, what if they are unresponsive and down?
Again, 50 feet up with a DJI Phantom Vision 2+. The subject dropped their high visibility orange shirt, a clue! We can see it easily on the edge of the field.
But, what if they dropped it in the field? Since you know it is in the frame, and since it is right next to the pilot, you can probably see it. If you were looking at images from 100 acres of soybeans how confident are you that you’d see this clue, particularly on a small screen?
If you are using a normal consumer UAV to search for an unresponsive subject in an area with significant vegetation your probability of detection may be rather low.
I think the UAV industry in general and the search & rescue community in specific should do a lot more work on designing and performing experiments with UAVs. Vendors and sales outlets keep touting their UAVs as being “good for search & rescue” without providing any data to support this claim, and often without really understanding SAR, SAR missions, and the challenges we face. (More on this in my upcoming presentation for NAASIC in Reno in September.) On the privacy side, people claim “he couldn’t see anything at 200 feet with that drone.” or the opposite position without sharing any data to support these claims.
Since I am an engineer, I like to gather data to support conclusions. And, for similar reasons, I usually form a hypothesis prior to conducting an experiment. Full disclosure – the data did not support my hypothesis. I’ll explain at the end of this post.
For the tl;dr folk – you cannot see much detail in a stock Phantom 2 Vision+ image when taken more than 50 feet above the subject.
This experiment was conducted with a stock DJI Phantom 2 Vision+. The lens specifications, according to DJI, are:
- Sensor Size – 1/2.3″
- Effective Pixels – 14 Megapixels
- Resolution – 4384×3288
- Recording FOV -110° / 85°
I had the camera set to use the “large” photo size and thus the full resolution.
The items in the frame are:
- A black Pelican case
- A human male wearing blue jeans and a reddish t-shirt
- A high visibility orange long sleeve thermal shirt
- A light blue t-shirt
- A white board with black writing on it
The sky was overcast and the winds were between 5 and 15mph out of the south east. I took the Phantom up to 25, 50, 100, 150, 200, 250, and 300 feet, +/- 3 feet as reported by DJI’s Vision app. At each altitude I took a single photograph. After landing, I used Photoshop to zoom in to approximately the same area in each image.
In the raw images viewed natively without any zoom:
- It is hard to find any identifying details of a human in the image above 50 feet.
- At 200 feet it would be hard to identify the human if you did not know what you are looking at.
Using the zoom tool in Photoshop:
- Detail is hard to discern at 100 feet and very difficult past 100 feet
- Given the subject’s pose you can determine that there is a human in the frame up to 300 feet.
- If you thought a drone would be invading your privacy when flown at 200 feet do you still feel this way after looking at these images?
- If you want to use a drone to search for missing people, do these images help you determine your mission parameters and effectiveness?
And my hypothesis? I thought more detail would be available further up. Glad I’m conducting experiments.
Image analysis is not my forte. If you have additional observations, please comment or share them with me directly and I’ll get them included.
I’ve been giving a presentation on the fundamentals of UAV forensics for several months, primarily for law enforcement and for other cyber security people. The presentation was recorded last month and is available on line.
50 minutes long but probably worth watching if you are interested in such things.
On July 17th, 2015, we were asked by the Tazewell County Emergency Management Agency to fly a UAV mission to collect aerial imagery to be used for damage assessment and storm severity determination. Within an hour of the request, we were on scene. All of the imagery was collected within two hours and Pekin’s GIS department processed and hosted the imagery within two additional hours. Call out to online imagery was five hours. Additional area to be covered would not have significantly impacted the total time required.
The ability to perform rapid deployment, collection and analysis workflows is crucial in emergency management settings. Our attention to processes, procedures, training, and relationships enabled us to perform this work efficiently and safely.
The swipe map version of the imagery can be found here.
[Written in 2005] I’m writing this en route from Istanbul to Munich after departing Dushanbe this morning. We’ll overnight in Munich and return to San Francisco at 6:30PM on Sunday evening. All told, we’ll have spent approximately 48 hours in aircraft in the last two weeks. We’ll also have spent at least 48 hours in various seats of a Toyota Land Cruiser while driving from Dushanbe in the west to Khorog in the east. There were an additional six or so hours sleeping on or in the Land Cruiser one night on the way back from Khorog.
This is just a random collection of thoughts and observations from our travels in Tajikistan. Very little in here is about search and rescue, which was the reason we were in Tajikistan in the first place.
Whilst in Tajikistan, we met a wide variety of lovely people from all walks of life; experienced international and (very) local cuisine, drunk more vodka in two weeks than we would in many months, met governors, seen Yo-Yo Ma and the Silk Road Ensemble, in what is probably the social event of the decade for Tajikistan; walked in the Pamir mountains, seen the stark contrast between rural Tajikistan and rural Afghanistan, experienced, first hand, the effects of the collapse of the Soviet Union 12 years later; accomplished our mission, and enjoyed ourselves immensely.
Hiring a cook/housekeeper is generally considered a luxury in my normal circles, but it’s almost a necessity in Tajikistan. When the power goes out most nights in Khorog by 6pm, and you don’t get home ’til 7pm, it’s very helpful to have someone prepare dinner for you at 5pm. Social occasions are few and far between with many people working six- and seven-day weeks due to the lack of social venues. Dinners are prolonged and enjoyed to the maximum. The Aga Khan party after the Yo-Yo Ma concert, held at the Choy Chana (lit: Tea House), had everyone dancing for three hours straight, something they’ll not find the opportunity to do again for a long time. The local music, food and dancing, I might add, was wonderful.
Some aid agencies, for a variety of reasons, have produced projects rather than long term, sustainable programs. This results in piecemeal implementations, failures to sustain the developed resources, and a sense of abandonment at times. My impression is that this is due to funding issues for the most part, but that may be a naive view based on very little time in the field.
The aid agencies are also the lifeblood of the country. Several years ago, the government only had 40% of the money required to operate itself. Aid agencies made up much of this shortfall, and significant infrastructure, educational and health benefits now exist in the communities due to them.
Tajikistan was initially considered an ex-Soviet republic and treated as a country that simply needed support until it could get back on its feet, free of centralized Soviet control. These days it is generally accepted that Tajikistan is more like a developing nation, and decades of aid will be required to put it firmly on it’s own two feet. This is causing a certain amount of turmoil within some of the aid agencies.
The Soviet times are remembered fondly. The roads were well maintained, food and healthcare were freely available, the population was extremely well educated (95-98% literacy rate quoted), and money was available for luxuries and entertainment. I have a travel brochure showing Tajikistan in the late 50’s, complete with modern ski-resorts and other travel destinations.
It took several years for people to realize that the Soviet Union wasn’t returning; “Maybe this is just a bad year; it’ll get better next year”. “Well, it’s a bad period, but we’ll come through it”. Eventually, they fell into civil war, further contributing to the decline of the country as a whole (Tank and APC hulks are plentiful along M-41, the highway into Khorog.)
I’m too westernized at the moment to be completely comfortable working in a developing nation. I am accustom to clean water from the tap, a wide variety of food, prepared in sanitary conditions; flush toilets rather than holes in the floor, water availability 24 hours a day, an endless array of entertainment, Internet access, my own car, etc… I found I could do comfortably without many of these things, particularly telephone and Internet access. My computer remained unused for 10 days and I’ve not spoken on a telephone in two weeks. My digestive system is artificially supported with Cipro at the moment due to three straight days of diarrhea. I’d eventually adapt to the pit toilets, I’m sure.
It’s worth noting that all of the travel advisories about “safe” eating, drinking, and sanitary practices while traveling are not designed for traveling outside what I’d call the Western travel infrastructure. You simply cannot avoid eating local food when you spend two days traveling by road from Dushanbe to Khorog. You might assume that at least the tea is “safe”, but it certainly isn’t boiled for ten minutes and water is frequently left in the bottom of the cup when it is initially presented to you, left over from washing it under the tap water or in the stream out back. It seems best to simply dive in, get sick, and get it over and done with.
Tajikistan Airlines operates one flight a week into Dushanbe, with a stopover in Istanbul on Saturday evening. They fly out via the same route on the same day. It’s a cash only operation; we showed up in Munich and had to raise $3,000 US very quickly to get on board. On the other hand, it is a very forgiving operation. I was carrying an IOU for $185 USD, payable to Tajikistan Airlines because we ended up short of the required amount. The gentleman at the counter later recognized me, accepted the $185, and we were even. Where else can you fly on an IOU!?
There are daily flights between Dushanbe and Khorog, although this, of course, depends heavily on weather and passenger demands. Flights into Khorog weren’t operating when we were heading out there, due to bad weather. The field is dirt, nestled between high mountains at a significant altitude. There are no instrument approaches and (I think) no landing lights. On the way back, there weren’t enough passengers from Dushanbe to Khorog to justify the flight, so there was no flight for us to return on.
Guesthouses are plentiful and people will open up their spare rooms to complete strangers. Teahouses can be found in most villages and I’ve eaten more bread and drunk more tea in the last two weeks than any year. Village leaders took us into their homes and served us nuts, tea, bread, fruit, and vodka. One of our hosts’ brothers was celebrating his birthday while we were visiting, and we spent the evening in a very traditional Pamirian house enjoying wonderful hospitality, including vodka with pilaf and yoghurt chasers.
This is a Muslim country but Vodka is commonly found among ex-pat and local communities alike. This appears to be a product of the fall out from the failure of the Soviet Union – A highly educated society with extremely high unemployment may well turn to alcohol.
The traditional Pamir house is built to be earthquake resistant. Five main wooden pillars support it, with a strong wooden frame supporting the roof. During an earthquake the walls may peel outward from the frame but the frame will remain standing. They’ll simply put the walls back up.
I noticed a common type of tree, resembling the Poplar, that is the primary building material for all of the GBAO (Gorno-Badakhshan Autonomous Oblast) territory, and perhaps most of the rural portion of the country. It grows straight and true and you’ll find it holding up ceilings, woven into fences, used in walls, supporting tables, cut and planed to become doorframes, etc…
Alternatively, rather than allowing the tree to grow and harvesting the entire tree, they’ll treat each individual tree as a renewable resource. It’ll grow to a height of between 6 and 10 feet before they’ll start pruning it back, encouraging it to send out multiple branches, each quite straight and true. These branches will be harvested periodically, resulting in a bulb-like growth at the initial pruning site. Imagine treating a tree as you would a rose bush and you begin to get the idea.
Magpies are everywhere.
Port Said, a local nightclub in Dushanbe, is the ex-pat place to be on Friday night. I missed it, but Jason and Kenyon enjoyed the experience.
There were some amazingly well constructed window frames throughout the area, obviously hand crafted from wood. They rarely had glass in them and only occasionally had plastic sheeting. Rather a striking contrast.
A small office building in Khorog: Two stories, new construction, two bathrooms, one kitchen, several other rooms, secure compound, goes for $350 per month.
A doctor in Khorog earns about $5 a month. Everyone supplements their income in a variety of ways, and many large families will live together under one roof to save money. Private language lessons in Dushanbe would be $2 or $3 per hour. For local labor the UN pays the best, then the NGOs, then the government.
The literacy rate is still in the high 90’s. They kept schools open after the fall of the Soviet Union and throughout the civil war. Most teachers weren’t getting paid then and, even now, they still earn very little.
During the winter, there’s only one road open from Dushanbe. The other goes through a high mountain pass and is closed until the weather improves enough for it to be cleared so, unfortunately, we did not get to experience it.
You drive from Dushanbe to Koloyb (sp) and pick up M-41 to Khorog. The total distance is approximately 730km and, on average, it takes people around 48 hours to make the trip. My comment, which elicited a fair amount of laughter, was that the road is simply a series of landslides connected by short strips of pavement. This is an accurate description.
The primary hang-up was at the first major river crossing, where the Neop River meets the Pyanj River, south east of Kulyab. The concrete span had been washed out two weeks prior and a slow effort was being made to repair it, but resources just weren’t available. The outage was also a significant boon to the local economy. Guesthouses and teahouses will have experienced a booming business as travelers waited to cross the river.
Crossing could be effected in your own vehicle, using a bit of luck, good equipment, and a lot of skill. The other option was the use of two vehicles, which were for hire. One was an ex-military transport with a very high wheelbase. There was one window in the back and the compartment filled with diesel fumes, but it would get you across the river safely. Your own vehicle would come across on the second truck, a flatbed.
This, of course, was assuming the vehicles were running. On the way out, there was the distinctive flash of an arc welder on the other side; the vehicle transporter was under repair. Thankfully, half our party was met by another vehicle on the other side and we were able to get across in the personnel transport. The rest of our party was stuck for two additional days. They attempted to cross the river on their own and found themselves wedged and flooded up to the dashboard. They were towed out and charged $100 and 20 liters of fuel.
World Food Program drivers were also stuck at the crossing. They were being charged $100 to transport their vehicles across. They’d no hope of raising this money on their own and so the agency was challenged to raise and get the money to them; a most unexpected expense all around.
The rest of the road is only one lane at best. Frequent wash outs, smaller river crossings, waterfalls, stuck vehicles, rockslides, and other hazards await the drivers; we blew two tires on the way back. We watched a group of people salvaging everything from a transport vehicle that had flipped over the side and fallen 60 feet onto it’s back. Another transport had left a trail of transmission fluid up a very severe slope and blown its transmission before it had made it to the top. Their load was staged at a landing further up the road, having been moved there piece by piece for hours. The drivers were camped out with it, waiting for someone to come and help them continue the journey.
Public transport along the road is by a series of taxies and buses. They’re all packed and people may have to wait for hours by the side of the road for a ride, as there is no scheduled service. The roofs of the vehicles are packed with identical, thin walled, durable plastic suitcases.
In every village along M-41, in Dushanbe and even in the more rural areas, women and children sit at small tables stocked with cigarettes, soda, candy, soap and other items. All the tables seem to have very similar stock. Larger stores occupy what were once cargo containers.
All supplies to Khorog come in via this route at the moment or via Russia through Osh, in Kyrgystan, via a route leading northeast and then back to the northwest out of Khorog.
We were inspecting a water project somewhere in the GBAO; they were building a flood control system. There were quite a few laborers around, and some people who seemed to just be watching. While I was standing a bit down hill from the bridge over the project, an old gentleman walked up to me and said something in Tajik. I explained in English that I didn’t speak Tajik, and in very clear, unaccented English, he very politely invited me to his house for tea. I was rather surprised and mumbled something about needing to stay with the group. He said the invitation was open and headed down the slope. I really wish I’d taken him up on his offer.
As mentioned, while returning from Khorog, we blew two tires. While changing the second one, a military transport came from the other direction, fully loaded with troops, including some hanging off the side. One of them, a young lad of about 20 years old, more Asian than Tajik in appearance, smiled at us and yelled “Good luck!” as the truck went by. We shouted back “thanks!” and watched the truck rumble off down the road.
Most of the soldiers are just kids, manning checkpoints or patrolling the roads. They’re generally very friendly, curious, and… well… nice kids.
The southern border of the GBAO is along the Panj River. On the other side of the river is Afghanistan. There are a number of checkpoints along this road, mostly very small buildings that I’d struggle to stand up straight in. In general, they’re manned by one solder in his mid to late 20’s along with several other younger soldiers, who are in their late teens at best. I guess this is a lot like U.S. forces in Iraq at the moment. Their uniforms are generally complete and as neat as can be given the situation. They’re armed with very worn AK-47s. The younger guys will frequently not have a clip in the rifle, and none is apparent on their web belt. They may or may not have a single round in the chamber.
The border is guarded by both Tajik and Russian troops. The Tajik troops, according to our guide, are KGB and the Russian troops may be too. Does the KGB still exist in Russia?
Coming back from Khorog, we hit the river crossing again and were blocked by lack of transport vehicles and high water. We made our way back to the village near by and stopped at the entrance to what appeared to be a military compound. Turns out we’re spending the night in the military barracks for the Russian and Tajik guards. They very generously open up the quarters reserved for visiting generals. They sweep out the room, wet the floor down a bit to knock down the dust, lay some bedding out, and make sure to bring us tea for dinner. It’s quite odd to be waited on by a soldier. Mind you, the quarters are about 8×12, have two beds, very poor walls, one broken small stove, and are already inhabited by a variety of animal and insect life. Kenyon slept on the roof of the Land Cruiser, Jason on the hood, and I slept in the back seat. Several other people from our group slept in the other vehicle, two people slept on the remains of a bunk bed outside, and several people slept inside. We were given an armed escort to the bathroom.
Most of the checkpoints were mere formalities. Sometimes they saw the NGO emblem on the truck and simply lifted the gate to let us pass. Other times they collected our passports and registered us – with one exception:
Second day out of Dushanbe and we’re at the last checkpoint before entering Khorog. We pull up to the checkpoint and all the soldiers are wearing black ski masks. There’s a guy in a foxhole about 50 feet back on our 7 o’clock position with a AK-47 on a bipod pointed right in our back window. Off at our 9 o’clock, up the slope a bit, another masked soldier was in a prone position with a sniper rifle pointing in our direction of travel. We decided this might not be a good time to take pictures. Never did find out what was going on but one person suggested that some high level officer was coming through and they were just making it look good. They certainly succeeded.
Humanitarian aid does flow into Afghanistan via Tajikistan. AKDN just completed a bridge over the river from Khorog and they had another one under construction several hours west along M-41 towards Dushanbe. In the meantime, they were running a huge number of food stores across the river in a pair of Zodiac boats under the watchful eye of the border guards. On the way back we saw the result, hundreds of bags neatly stacked up on the Afghan shore, waiting transportation deeper into Afghanistan.
All along the Panj, on the Afghan side, runs a foot trail. It winds, climbs, dips and crawls along the cliff faces and flats. It’s carved out of slopes that are nearly vertical, persists past landslides and avalanches, and is the major road for dozens of villages. People and donkeys could frequently be seen traveling the route.
Afghanistan never had the benefits of a centralized Soviet economy and thus learned many years ago to make better use of their land. Same people, same geography, but the Afghans make extensive use of terracing to create more land area for crops and the Tajiks rarely use this technique, though they seem to be picking it up now.
Driving through the region for many hours I developed a much clearer understanding of why the Soviets failed to conquer Afghanistan. It, and the GBAO, are extremely mountainous and badly suited to moving armor. Any attempts to fly aircraft low would bring you below the mountain ridges, greatly increasing the exposure to shoulder-fired missiles from above by very, very tough and durable people.
Of course, terrain and weather that makes it difficult for modern military operations, also makes it a very interesting area for conducting search and rescue: We were talking with one guy who worked for MSF (Medicines Sans Frontiers, Doctor’s Without Borders). He told us there’s one village experiencing an epidemic.
“MSF simply hasn’t been able to get into it for over six months due to its remoteness,” He said, “the road is still buried in snow.”
MSF is pulling out at the end of the year. I need to go and learn about them, but it appears that they only operate in areas still experiencing civil unrest. They feel that Tajikistan is stable enough for them to pull out and move onto the next. I’m not sure the U.S. embassy would agree.
People have been registering domain names for years and many years ago someone realized that being able to anonymously register a domain name might be a good idea. There is now a proxy system in place that enables the owner to provide their real contact information but to hide it from casual observers. And there is a recent fight to keep this system in place to help prevent web site owners from being doxed and swatted.
The FAA probably should have considered doing something similar before requiring N numbers for all UAVs. Huh? Unless you are a pilot, or have gone through a Section 333 petition you probably didn’t know that most aircraft require an N number. That number is prominently displayed somewhere on the aircraft and it associates the aircraft with a specific person or organization for all the world to see.
So what is the privacy issue? “All the world to see.” Try this:
- Go to the FAA N number query site – http://registry.faa.gov/aircraftinquiry/NNum_Inquiry.aspx
- Click on “Make / Model”
- Enter “DJI” in the “Manufacturer Name” field
- Find an entry where the name field is just “DJI”
- Click on one of the states listed in the second column
There is potentially a lot of personal information there, particularly if you didn’t know what was going to happen when you filed for your N number. When I applied for a 333 exemption, I did so as a company and the company’s address is not my home address. Sure, someone can still work their way back to my physical location but why make it easy?
Two take home points:
- If you can, file for your N number using an address that is not your home physical address
- The FAA clearly didn’t think ahead when requiring N numbers for UAVs. Let’s guess that there will be 500,000 UAVs flying in the US within five years. That is a lot of paperwork to file for all those N numbers, and a lot of personal data available to innocent or malicious people
Maybe the FAA should take a tip from the DNS world and provide a proxy service for UAV operators? I agree that the data should be collected (and this may not be a majority opinion) but I also feel that it should be somewhat protected.