Camera Positions On An Orthomosaic Map
Walking The Tight Rope, The Fine Line Between Too Much And Too Little
Less is more… sometimes. Creating orthomosaic maps requires balance. Balancing the size of the project, the amount of front lap, side lap, altitude, and time- both the time of the flight and the time for uploading and processing. So when planning a project it’s important to ask some questions.
What is the purpose of this map? Is it going to be used for measurements and planing or is it just going to be hung on the wall as an aerial picture? How much area needs to be mapped?Obviously the larger the map, the more time the project will take, and each picture taken is just going to be adding to the total file size that needs to be uploaded/ processed.
On the other hand if you have insufficient coverage you’ll have wasted your time and the customers time.
Your map can only be as accurate as your ground sampling distance (GSD). For us, we try to maintain a 1” per pixel resolution so depending on your camera the altitude you fly at may be higher or lower but basically it’s going to be a set variable. On Ground Station Pro you can see the approximate GSD when your setting up a flight.
Overlap is essential but again there’s a sweet spot between too much and too little. Too much and you start creating unnecessary amounts of data, too little and you risk losing data and having holes in your map.
It’s been said that photogrammetry is as much an art as it is science. So there’s no substitute for experience, making some mistakes and using good judgement. As consultants, we’re here to help with all your mapping needs and questions so feel free to contact us, but either way, remember that balancing the amount of area and data that you collect is a big piece of the photogrammetry puzzle.
“How far away can you fly that thing?”
We get asked that question a lot and I always find it a bit puzzling. The whole point of using drones for commercial purposes (as opposed to military purposes) isn’t to see haw far you can fly. It’s really about the vertical perspective. For that, you don’t need to go very high or very far.
Let’s say you have a mapping job of 500 acres. For a takeoff location I would look for the highest point and hopefully one that is fairly close to the center of the project. Your drone will never be very far away so you maintain a stronger signal and clear VLOS. You also will get the most working flight time out of each set of batteries since less time is spent flying to the far end of the property and back.
Same thing goes for inspections. Why make inspections from as far away as possible when simply being out of harms way allows you to keep a closer eye on the UAV and have the best video quality?
Here’s the main point: Looking for ways to keep your drone closer to home will be safer, more efficient, and allow for better video quality. To us, that’s way more important than setting distance records!
1 Step Towards Smoother Video Footage
Shooting video from a drone is awesome. While EPIC is mainly a inspection and mapping company we’re not afraid to get out there and make some marketing or training videos with a variety of equipment. To be honest, I find cinematography both fascinating and rewarding while at the same time being demoralizing and maddening.
There’s few things worse than thinking “I got the shot” only to find upon review that the footage had some horribly unnatural movement at a critical moment. Sometimes this has happened to me because my finger wasn’t quite positioned right on the stick and when I tried to adjust it… I ruined the shot.
So, what is a one simple step in the right direction? Of course, learning to be light on the controls is a good idea. You can also select the “tripod” intelligent flight mode which basically reduces the sensitivity of the controls, but one thing that can really smooth out your videos and boost your flying skills, is learning to fly in ATTI mode.
Attitude (ATTI) Mode
First we have to say: Don’t do anything you’re not comfortable with, don’t do this on a windy day, don’t start out near any obstructions, and flip the switch at your own risk. There.
OK, so what is ATTI mode? ATTI mode disables the direct influence of satellite positioning. Think of it like this: Position mode is like riding a stationary bike, when you stop pedaling, the wheel stops moving. ATTI mode is like riding your bike outside, when you stop pedaling, it coasts but you can still hit the brakes and depending on the wind and ground slope you may find it easier or harder to stop. Riding inside is definitely safer, riding outside feels more natural.
Generally, if we’re making a video and someone says “that’s a nice drone shot”, as the camera operator, to some extent I feel like I’ve missed the mark. I’d rather you not even be thinking about the position of the camera. It’s like trying to blend in to a crowd, nothing makes you stand out quicker than awkward suspicious movements. And there’s where ATTI comes in, the more natural the movement, the less distracting and more opportunity your audience has to focus on the content, not how you got that particular shot.
Trying It Out
- On a nice day, find a good open area and try some sliding shots going past some trees or something else.
- Do some reveal shots (camera pointed down while you fly forward then slowly pan up)
- Try flying in a direction and letting the drone slow itself down gradually while you pan to a side.
- Pick an aerial shot from your favorite movie or YouTube channel and try to recreate it with your drone.
- Just get creative and come up with your own shot!
Making a difference
There is of course many other things that can make a difference, not the least of which is good old practice. In some further posts we’ll address those but the fact that you read this far means you must care about your drone videoing skills and for that we say: Rock on!
Stay safe, and keep pressing that record button!
Searching For A Broken Water Line
Knowing your limitations
Today I wanted to talk about some of the limitations of Infrared Thermography. We’ve been called out several times to locate water leaks for customers, sometimes its been a success, other times we find nothing conclusive. What makes the difference?
You can’t see, what’s not there
Imagine that you have very poor eyesight (if you do have very poor eyesight I’m sorry but you may understand this even better) a pair of corrective lenses can make all the difference when reading this page. But suppose we change the color of the letters in this article to white, will you still be able to read? Your glasses are great but they can’t help you see what isn’t there.
Infrared technology is like those glasses. It’s wonderful, it can open up a whole new world of possibilities, but it can’t help you see what isn’t there. What allows you to read this text is the contrast between the dark letters and the light page. If the letters and the page are the same color, there’s nothing to see, and if the temperature of what you’re looking for and what’s surrounding it is the same, you’re wasting your time. Even if the information is there it will be camouflaged.
At times the temperature of the water line we’re looking for and the surrounding ground is simply too close to provide any usable data. That is a limitation of infrared. It’s nobody’s fault, you simple can’t read what isn’t there.
Another issue can be when a line is too deep. In our most recent case the water line was 4’ bellow the surface and much of it had just been paved over. That was two infrared strikes against us! In that case the infrared radiation simply can’t get through in the same way that sound waves can’t make it through a sound proof wall.
In a different scenario, the line break was thought to be under a concrete slab which also had a thermal blanket between the ground and the concrete. Again, nothing to see here. The information may be there but it’s completely blocked. Like a person screaming at you from behind sound proof glass, you can tell somethings up but you can’t make out any words.
So there you have two basic reasons why an infrared inspection may not turn up anything. Infrared, like everything else, has it’s limitations, however, it also can see things that would be impossible to discern without it and it’s a powerful tool for seeing a whole different dimension of light. Like so many things in life, knowing your limitations is as important as knowing your strengths.
What was special about this job? It was scooted right up against an air force base making it a definite “no go” for drone pilots. But with some hoop jumping and proper forms nearly anything is possible and this was no exception.
Everything came together nicely. The FAA granted our authorization. The day before the flight ATC was contacted and given the details of our operation. We communicated with them again right before takeoff and right after the job was done so that everything was done safely and professionally.
Lessons learned: Sometimes being in the right place at the right time is all about hard work, being committed to safety, and following proper procedures
Facility Management (FM) is rapidly evolving. The Internet of Things (IoT) is becoming the new reality and BIM (Building Information Modeling) is creating exciting possibilities for augmenting that reality. How can laser scanning help FM teams? Increasingly FMs are on the go and a major advantage of 3D technology is the ability to take your facility with you, improving communication and decision making. Bottom line: utilizing laser scanning makes INFORMATION more valuable than your LOCATION.
Photogrammetry or Laser Scanning?
Which is better? The term “better” really implies that one of the two is inferior, but in truth, that’s not necessarily the case. Comparing the two technologies is like comparing dogs and cats, they’re two different species with different strengths and weaknesses, you can’t compare them, you can’t even know for sure which one would win in a fight!
So what are the differences between these two things? Photogrammetry is a passive form of collecting data, meaning, you’re not sending a signal you’re just picking up available light from the surface. Your accuracy is dependent on being at the appropriate altitude, with the appropriate camera and settings and collecting the data at the right time of day. Further, you can utilize ground control points (either pre-existing ones or ones that you provide such as Aeropoints) to increase your global accuracy and provide ground truth information- checks and balances. The information you receive is in the form of pixels, and if you set up your altitude correctly, one pixel should equal about one inch of ground which is also known as the images Ground Sampling Distance.
Laser scanning is actively collecting information. As the mirror spins, the laser is being sent and bounced back at a mind numbing speed and those millions of points are being translated into 3D information. Just like a printed picture is made up of millions of little dots, the picture that the laser produces is made up of millions of tiny points of light. Accuracy can be as close as + or – 1 mm.
So what’s the bottom line? This is just a very brief, simplified look at these two options. They both are good. Laser scanning will tend to have a higher level of accuracy but photogrammetry will have a nicer “look” to it. Cost is also a consideration, and speed. Really though, they don’t need to be opposed to each other, in fact, Laser and Photo can be combined depending on the situation giving you the best of both worlds. At EPIC, we’re proud to have both technologies at our disposal!
Did You Know? How Surface Structure Effects Accurate Temperature Readings
You shouldn’t judge a book by its cover but when it comes to getting accurate IR temperature readings it’s all about what’s on the outside. So for instance, if you have a stainless steel pipe that is running at 100 °F and a flat painted pipe also running at 100 °F, which one will appear to have a higher temperature? If you said the painted pipe, you would be correct but you also might wonder why you were correct. There are several things that effect accuracy but we’ll just look at one: Surface Structure.
Let’s get one thing out of the way right off the bat; emissivity is the single most important factor for reading apparent temperature. So what is emissivity? Simply put, it’s the amount of energy emitted by an object. Some materials have a high emissivity, rough surfaces, painted surfaces, non-metals; these will all tend to emit a more accurate picture of their true temperature. You could say they’re an open book, what you see is what you get.
Now in contrast, glossy materials (like the stainless steel pipe) are not very good emitters because their too preoccupied with being good reflectors (no one can be good at everything) and therefore they may give you a better idea about the temperature of things around them than their own temperature.
What’s the main point? If you’re going to take a reading on a highly reflective surface you need to either compensate for that in your camera i.e. adjust the emissivity settings, or place something that is a good emitter on the surface and then take the reading. Electrical tape has an emissivity of about .95 which makes it a handy tool to keep around. Just slap it on the surface and you’re good to go. Another thing you can do is find an area with lots of corrosion which is also a good emitter and use it for your thermographic exploits. Just remember, with thermography, it’s what’s on the outside that really counts.
That’s all for today, now get out there and soak up some infrared radiation!
Different Color Palettes, It’s Not Just About Looking Pretty
There’s no way around it, looking at the world through an infrared camera is cool, really cool. Even just looking at hot water coming out of a faucet feels like you’re watching molten lava pour into the sink and down the drain. Of course, what you’re seeing is just a representation of the infrared radiation and that representation can be dressed up in different color schemes depending on the situation and your preference.
While not all cameras have exactly the same options, here’s a brief rundown of three FLIR color palettes.
This is the original palette used with IR (Infrared) imaging systems and it’s still a favorite for many thermographers. The focus tends to be a little clearer and it’s great for seeing fine spatial detail. However, as you can see in the picture, it’s not as good for easily spotting small temperature differences.
Ironbow is a good, popular, all-around usage palette. It has a nice balance between spatial detail and thermal detail. Small temperatures will show up more readily and it has a nice intuitive appeal for non thermographers.
Rainbow High Contrast Pallet
As its name suggests, the rainbow pallet introduces more colors into your picture. It’s great for showing maximum thermal contrast and highlighting potential problems for a customer.
So in the end, color palettes are a very useful tool. Use them in real time during inspections, or in post processing and when generating reports. Use a variety and choose the one that’s right for:
1. The type of inspection
2. Personal preference
3. The needs of your customer
How To Identify Thermal Anomalies
A thermal anomaly is a fancy way of saying that there is a noticeable temperature difference. You may not know why, or even if it’s a problem, but you know there’s a difference. The problem is, sometimes things that seem to be anomalies are really just thermal reflections. You can think of it this way, if you were trying to shoot a video of a person looking in a mirror where would you stand? If you stand directly behind them your own reflection is going to end up in the picture, so you would need to stand to one side. Problem solved.
Something similar happens when looking at infrared radiation. Stand directly in front of what you’re scanning and your own thermal reflection will show up. Another big thing that can throw you off is the sun. In this video you can see two things that might seem to be anomalies but as the drone moves you’ll notice one “hot spot” moves with it. That’s the sun. The area that stays consistent as we move is the anomaly.
So it’s really a very basic concept. If you think you’ve found something out of the ordinary just move a little, take the reading again and see if your getting the same results. It’s also good to keep in mind that certain surfaces are going to be more reflective than others, meaning your not getting the full thermal story when you look at them, instead your seeing more reflected radiation than the object is actually emitting. Long story short: don’t be afraid to move your feet (or your drone) to get a more accurate reading and take into account the surface properties of whatever your looking at.