Info & How-To Articles

UAVs are complicated machines, and it’s a true feat of engineering to be able to design and build them feasibly. To do so, however, requires an in-depth understanding of the underlying physics. A UAV has to be able to sense it’s position, velocity, acceleration, and many of the other variables that describe it’s motion. All of these ideas are clearly defined and described in the laws of physics, and understanding them can answer many questions about UAV flight characteristics. In this article, we’ll focus on VTOL (Vertical Takeoff and Landing) UAVs like our Draganflyer X6, but the same concepts apply to all other air vehicles and UAVs.

Some Basic Concepts Explained

Before we can explain more complicated ideas (like how airfoils and accelerometers work), an understanding of a few basic physical principles is needed.  These include force, mass, and acceleration. We’re going to skip a more thorough explanation (which would require calculus), and instead use a purely algebraic approach.

Mass

Mass is a quantity that defines how an object interacts with a gravitational field, and how acceleration, momentum, energy and similar concepts work. Mass is commonly associated with weight, and it’s true that an increase in mass results in an increase in weight, but they are two separate concepts. Weight is a force – a push or pull on an object, while mass is a quantity intrinsic to a particular object. The SI (International System) unit of mass is the Kilogram, equal to a weight of 1000 grams. Kilograms are different from pounds – a pound is a unit of force, which we will describe shortly.

Velocity

Velocity is often used as a synonym for speed, but as with mass and weight, they are two separate ideas. Speed measures how fast something is moving, without reference to the direction that it’s traveling. Velocity keeps track of both speed and direction, giving a more complete picture of the behavior of an object. The direction is given as an angle, measured with respect to some reference. Angle usually has units of degrees, of which there are 360 in a complete circle.

Acceleration

Acceleration describes the rate at which velocity changes. You can find the average acceleration of an object by dividing the change in velocity (delta V) by the time interval in which that change takes place (delta T). The result becomes more precise as you let delta T and delta V get smaller, and as they become infinitely small, the calculation becomes precise. Acceleration is measured by an electronic device called an accelerometer. Our Draganflyer X6 UAV has 3 accelerometers, which measure acceleration in the X, Y, and Z directions respectively.

Acceleration takes into account both the change in speed and the change in direction, making it a vector quantity as well.

Force

Now that acceleration and mass are understood, we can define force. Loosely, force is a “push” or “pull” on an object. Mathematically, force is the product of mass and acceleration (also known as Newton’s Second Law). This makes sense intuitively: the force required to move an object gets larger as the object gets heavier, and it also increases if you want to accelerate it faster.

From this, we can see that applying a force to an object with mass will result in an acceleration, and in order to accelerate an object, a force must be applied.

It may be hard to believe, but these few concepts are actually all you need to understand the basic physics of aircraft and UAV flight. New concepts are built upon them, but these same principals are fundamental.

UAV Flight Equilibrium

Equilibrium is a state of motion where all forces balance, canceling each other out exactly. Because any force on an object causes an acceleration, so if an aircraft is to remain in one place all the forces acting on it must add to 0. So how does this happen?

Let’s start by imagining a generic aircraft, that is currently hovering in one place. The forces acting on it are:

• Gravity, pulling downwards
• Thrust from the motors, pushing upwards

We will neglect airflow, torque from the propellers, or any other force that acts sideways.

In order to hover without gaining or losing altitude, the thrust from the motors must equal the force of gravity. This is shown graphically on the right. The gravitational force is represented by the green arrow, and the lift force provided by the motors is shown by the orange arrow.

This concept becomes immediately useful. For example: the Draganflyer X6 weighs 1000 grams, so the motors and propellers need to provide exactly 1000 grams of thrust downwards to keep the UAV in a hover.

Obviously, the forces don’t always have to balance. If we wanted the UAV to turn, that imbalance has to be created. On the Draganflyer X6, this is done by spinning one of the propeller sets faster than the other two. This creates an excess force on one side of the aircraft, resulting in an acceleration. It’s this acceleration of one side of the aircraft that allows the turn. Once the aircraft is banked, all the thrust from the motors is directed away from the downward direction, allowing it to move relative to the ground. When we desire the motion to stop, the UAV banks in the opposite direction.

Error Measurements

Every measurement has an error of uncertainty associated with it. It’s theoretically impossible to measure something with absolute precision. Because of this, all of the instruments built in to the Draganflyer X6 have an error tolerance associated with them. This error can be estimated as the smallest graduation on the measuring device. The magnetometer, for example, is capable of measuring to the nearest degree. This error may increase due to external influences, such as electric equipment operating nearby.

Because every instrument in the IMU has an error bar, the flight computer can’t be 100% sure of the UAVs position at any given time. This means that if you let go of the controls, the UAV will drift off of the position that you left it in. It’s simply a consequence of the physics involved – no amount of engineering precision can change the fact that there will always be an error in the instrument measurements.

In a well designed aircraft, errors are handled well so that their effect on flight performance is minimal. In the Draganflyer X6, for example, the uncertainty in GPS position is always displayed on the handset, and trim tabs are provided to cancel out any unwanted movement. We’ve taken every possible step to minimize the effect of errors, and display them to the user.

Applications to UAV and Aircraft Design

All these concepts are important, but how are they applied to UAV design? Well, we know from Newtons Second Law that any force results in an acceleration, which is just a change in velocity. UAVs need to control their position and velocity, so there must be some means of obtaining and processing this information. Our Draganflyer X6 UAV does this by using the following:

• A magnetometer to measure heading
• 3 accelerometers to measure acceleration
• A GPS to find position and velocity
• A barometric pressure sensor to measure altitude

Combined, all these sensors can be considered an “inertial measurement unit”, or IMU. Data from each of these sensors is processed by the flight computer and used to make altitude, heading, and speed corrections.

The physics behind how the Draganflyer X6 UAV works are complicated, but these simple ideas should help you to understand why it behaves the way it does, and the degree of understanding required to build such a complicated machine.

Panasonic has recently released a firmware update for their DMC-LX3 series digital cameras. Most cameras are shipped with firmware version 1.2, and upgrading to version 1.3 will unlock several new features, including:

• The auto white balance function has been improved.
• The camera recovers gracefully if turned on with the lens cap still in place.
• The MF ASSIST/AF area selection has been improved.
• The display of manual exposures has been improved.

Firmware version 1.2 works, but it’s always a good idea to keep your camera running at the latest version. Here’s an easy – and free – way to upgrade the firmware and improve your cameras performance.

To Update Your Camera’s Firmware:

1. Fully charge the camera battery. If the battery runs out of power while the firmware is installing, it’s very likely that you will make the camera un-usable. The camera will display “no valid picture to play” if you try to update the firmware with a partially charged battery.
2. Check your firmware version. If you already have the latest firmware version, you don’t need to update. Check your version by pressing “menu / set”, then scrolling to settings, and then selecting “Version Disp.” You only need the update if your version is less than 1.3.
3. Download firmware version 1.3. Click either the Windows or Mac version (depending on your operating system) on Panasonic’s site, and download the firmware to your computer. The Mac version comes as a zip file, while the windows version is a self extracting executable file. Unzip the mac version, or run the windows version, and find the resulting .bin file. Make sure that the .bin file size is exactly 6,096,384 bytes. You can check this in Windows by right clicking the .bin file and selecting “Properties”. The file size on disk will be slightly different, but that doesn’t matter. Only the actual file size is important. Checking the file size makes sure that you don’t have a corrupt copy. If you find the file size is different, try downloading the file again.
4. Copy the firmware to an SD card. Make sure that there are no files on the SD card, and that it’s been formatted to work with the camera. Formatting instructions can be found in the camera’s instruction manual. Once the card is ready, add the .bin file that you downloaded.  If your computer doesn’t have an SD card reader / writer, use a portable USB one, available at most computer stores.
5. Set up the camera. To update the camera firmware, several switches have to be in the correct position. With the camera OFF, slide switch “C” to the  position, and move switch “B” to the playback position (NOT the position). Insert the SD card you prepared earlier and turn the camera on by sliding the power switch to the “on” position.
6. If you’ve followed the above steps exactly, the camera will now display “Please wait…”. After a few seconds, a menu asking “Start version up?” will be shown. Select “yes” using button “A” and press menu / set to confirm.
7. The firmware will now update. It is critical that you don’t touch any of the camera buttons during the update process. After the update finishes, the camera will reboot (power off and then on again) and resume normal operation. You can tell that the firmware update completes when you see the camera screen power off and then back on. After the update finishes, the warning not to touch the camera buttons will disappear.
8. Verify that the update was successful. You can verify that the firmware update was successful by navigating to the version display item in the setting menu. It should display version 1.3.

Congratulations! You’ve just updated the firmware on your Panasonic LX3 series digital camera. The new firmware will keep your camera up to date, and give you access to all the latest features.

Enjoy using the Panasonic LX3 for your RC UAV aerial photography!

Digital cameras are versatile devices, capable of recording images in many file formats. Common formats include JPG, BMP, TIFF, and many others, and their relative advantages and disadvantages are explained here.

What Is a File Format?

Simply put, a file format is just a particular way of encoding information for storage in a computer file. Computers are binary devices (operating with a number system of only 1′s and 0′s), so file formats can be thought of as a way to convert back and fourth between the original information and it’s binary representation. There are many different file formats, and some are more flexible than others. For example: the GIF file format can be used as a container for images or simple animations, while the JPG format can only store simple images.

Different file formats are identified by what’s called the file name extension. Adding a dot to the end of the file name and appending the abbreviation of the file format lets both people and programs know what the file format is. Changing the file extension doesn’t convert the file to another format though – it’s best thought of as a “note” or reminder of how to treat the file.

File formats are also identified by internal markers, usually strings of characters in the header of the file. Using different methods to identify the file format helps to ensure that it’s always handled correctly.

Why There are Different Image File Formats

When an image is downloaded from a camera, it’s encoded as different lighting and color levels for each pixel on the camera’s charge coupled device (CCD) sensor. All digital cameras have a CCD chip, which consists of an array of light sensitive pixels. Each pixel generates an electric current when a photon strikes it, known as the photoelectric effect. This current is read from each pixel and then recorded in memory as a series of light levels and colors. Obviously, a long list of numbers isn’t a human readable image. Most often, this RAW file format is immediately converted to one which is more easy to use, such as a JPG or TIFF. The image can then be read by a computer and printed or rendered on a screen.

There are different image file formats so, depending on your project, you need to compromise between image quality, file size, and many other parameters.

Comparing File Formats

With so many different file formats to choose from, it’s useful to understand what each is designed to do, so that you can use the right ones for your project. Here are some of the most common:

• JPG / JPEG – The name JPEG stands for Joint Photographic Experts Group. It’s a “lossy” file format designed to compress image data, reducing the size of the resulting file with a minimal loss of image quality. JPEG is a standard, ISO certified file format, and is commonly used to transmit images on the internet. Because of this, it’s one of the most commonly used formats on digital cameras. The small file size allows a large number of images to be stored on a single memory card, making it convenient to use.Whenever an image is stored in the JPEG file format, some information is lost. Because of this, JPEG is not suitable for usage where the exact replication of the original image data is required.
• BMP – The BMP, or bitmap format, is one of the most simple. It does not compress images, and stores image pixels with a color depth of 1, 4, 8, 16, 24, or 32 bits. For example: a 32×32 thumbnail image appears small when displayed on the screen. Enlarging the image will show each pixel as a large block, reducing the image quality. BMP is not a lossless format, and the large file sizes make it unsuitable for transmitting over the internet or storing on small memory cards.
• TIFF – TIFF stands for Tagged Image File Format. Designed to store images such as photographs and line art. The TIFF file format specification is currently owned by Adobe Systems. TIFF was designed to encode image data simply, in a single file, through the use of header tags defining the image size and other parameters. TIFF is a lossless format, meaning that no image information is lost when the file is compressed. This means that it can be edited and re saved without losing quality. TIFF is the preferred format for high color depth and high quality digital cameras. The files produced using the TIFF format are generally larger than equivalent JPEG files, but this is because of the lossless compression used by TIFF.
• GIF – The Graphics Interchange Format is a bitmapped file format, supporting 8 bits per pixel and a reference palette of 256 unique colors. The GIF file format can be used to create animations, and is sometimes used in websites. The GIF format is not used in digital photography, because of it’s quality limitations.
• PNG – The Portable Network Graphics format is similar to the GIF format, in that it uses lossless data compression, but PNG does not support animations, and it can use more than 256 colors.
• Raw – The raw file format is significantly different than those mentioned above. It’s relative advantages and disadvantages are discussed below.

The Raw File Format

A raw image file contains the minimally processed output from a digital camera’s image sensor. Raw images are not ready to be printed or edited with graphics software – they must be “developed”, or turned into a different format first. Raw images are best thought of as film negatives- they aren’t directly usable as an image, but contain all the information necessary to create one.

So why would you use a raw image? It turns out that every JPEG or TIFF you download from a digital camera was a raw image at some point, the camera just converted it. High end cameras allow users to control how their images are “developed”, but the amount of control you have over the process is usually fairly limited. In this conversion process, some of the raw information about what the camera saw is always lost.

If you’re interested in seeing exactly what the camera saw, without losing any information during processing, then using the raw image format is the best option. Raw images give the photographer a great amount of flexibility, allowing you to precisely control the brightness, contrast, sharpness and other variables. Using raw image files can help you capture the detail that you wouldn’t otherwise get if using a processed image format.

Here are some of the benefits of raw image files:

• Higher Image Quality – All the processing takes place in one step, improving the final image quality.
• Better Intensity Information – Raw image files have 12 or 14 bits of brightness information, as opposed to the 8 bits a JPEG can provide.
• Finer Control – When you “develop” your raw image files, you have complete control over many of the variables, including brightness, contrast, and many others.
• Remove Unneeded Processing – Most digital cameras do additional processing on the images they take, including sharpening and noise reduction.
• Better Manipulation Possibilities – Transforming images in large ways, such as by increasing the exposure of an underexposed image can result in artifacts. Using raw images minimizes these, because the image has not already been pre processed.

Raw image files also have a number of disadvantages, the most notable being the large file size. Raw Images are typically 6 times larger than an equivalent JPEG, which reduces the number of pictures that can be stored on one memory card. It also takes more time to download a raw image from the chip and write it to a memory card, necessitating the use of more expensive camera equipment.

Unlike the other, processed formats mentioned here, there’s no one specification for a raw image. Camera manufacturers use different formats for their products, and the formats are often un-documented. There are several free projects under development that can read raw image files, most notably the GIMP (GNU Image Manipulation Program). Dcraw is also capable of reading and editing many raw file formats. Both these programs run on Microsoft Windows, and UNIX like operating systems including Mac OSX.

Aerial Photography Police Applications of The Raw File Format

For any police or law enforcement organization, collecting aerial pictures as evidence is best done in the raw format. When you are obtaining evidence, you don’t want to miss a single detail. The raw file format was designed to faithfully record everything that the camera sensor sees. With the raw file format, you are guaranteed that you don’t miss any detail in your pictures due to processing.

Because the white balance and other settings are not set when the camera takes the picture, they can be adjusted after the images are taken to ensure maximum image quality.

Our Draganflyer X6 UAV was designed to give users the maximum choice in camera equipment. Because of this, it can be equipped with the Panasonic LX3 digital camera, which supports output in the raw format.

At the time of writing, both Adobe Photoshop CS3 and Sikypix support the Panasonic LX3 raw image format.

If you cannot see the document below please download the document as a PDF

Rotary Modeler Magazine, one of the leading magazines in the RC helicopter industry, has written a 10 page, detailed review of Our Draganflyer X6 UAV. The review discusses all aspects of our latest unmanned aerial vehicle, including applications, construction quality, flying properties, and the included flight accessories. The X6 UAV got a rave review, with the authors citing it’s simplicity, functionality, and versatility.

The reviewers were impressed with our optional FLIR infrared video camera. The small FLIR camera is the most sophisticated cameras available, being able to see in the dark and spot people from a great distance. Here’s what the reviewers had to say:

“With either of these cameras, people “leap” out of the video even from great distance. As a result, these cameras are perfect for search and rescue operations and over the years have been responsible for saving many lives.”

Thermal Infrared cameras like the Photon 320 and 640 used to be large, cooled units that required a huge amount of power to operate. Now, camera technology has advanced to the point that we can install and deploy a FLIR camera on a small unmanned aerial vehicle (UAV) such as the Draganflyer X6.

The reviewers also noticed the build quality and design simplicity of the unmanned aerial vehicle, commenting:

“When you remove the X-6 from the case you can immediately appreciate the simplicity of the design, making this a very robust and easy to maintain aircraft.”

The reviewers were very impressed with the bright OLED display screen built in to the transmitter. You can see the screen clearly, even in direct sunlight, ensuring that you don’t miss critical flight information due to glare.

All in all, the Draganflyer X6 got a great review. You can read the review by picking up a copy of the May/June 2009 issue of Rotary Magazine, available from Rotary Magazine’s Web Site and most hobby stores.

Is your company or organization technically fit? What if you were to look at your business and see what new technologies and equipment you have acquired over the years how much of it is just sitting there and how much of it is used? Many business and public sector organizations acquire new technologies and equipment to assist in improving production or other sectors of their business. Some of the technologies greatly improve the way the business functions. In other cases, while the capability for the newly acquired technology to improve the business is there, for one reason or another it is simply not used. If the latter is the case, it may be due to the company being “technologically unfit” in the use of that equipment or technology.

Much like being physically unfit, being “technologically unfit” may be the result of a combination of several factors including; inadequate training, an inadequate number trained personnel or inadequate use. With some technology the old adage of “use it or lose it” is a very appropriate saying. In situations where time is of the essence, it is not a time to learn how to use the technology or to make critical errors with it due to lack of experience.

Let’s look at the factors for being “technologically unfit”.

Inadequate training. This may be the result of lack of actual instruction or being unable to devote the necessary time to practice with the technology to acquire competence in its use. If sufficient time is not allotted for personnel to gain the skills to competently use a technology, if improperly used it can become a liability.

Inadequate number of trained personnel. Often it is practise for a company or organization to only train one or two personnel in the use of a technology. This may be fine if the personnel assigned this task are going to be able to cover for one another, but what happens when those personnel are unavailable due to other job commitments, sickness, vacation or if they are transferred or quit. If there is nobody trained with the technology to replace these personnel, then it is of little value.

Inadequate use. Inadequate use can occur from the lack of opportunity or situations for use or due to the lack of adequately trained personnel. If this is the case, it is important to continue utilizing the technology in regular practice or scenario type of training to avoid losing the acquired skill necessary to utilize the technology when needed.

So use it or lose it, the choice is yours. However to use it you need to be prepared to give sufficient personnel adequate time to train to become proficient. Otherwise you may just have a lot of technology just sitting there doing nothing for you.

Introduction

Aerial photography has been used since the first hot air balloons to give a new perspective to the objects and landscapes in our world. With the modernization of both aviation and camera technology, a new type of aerial photography was born. RC aerial photography uses ordinary to advanced RC aircraft to carry a camera payload and obtain aerial pictures. RC aerial photography has evolved into both an exciting hobby, and a thriving business.

RC aerial photography can add a new perspective to images of large objects. by showing the large scale relation between different objects. Many engineering, mapping, and surveying projects depend on a clear understanding of the large scale properties of an area of land, making aerial photography the perfect tool for obtaining this information. Traditionally, aerial pictures were obtained by sending a human photographer on a flight in a full scale aircraft, usually either an airplane or helicopter. This is a time consuming and inconvenient, because aerial photography is affected by rapidly changing weather and lighting conditions.

RC aerial photography is a simple and cost effective solution. You can rapidly deploy and recover an RC aircraft, and get aerial pictures of equal to (and in many cases better) quality than those taken from a full scale aircraft. Conventional aircraft are limited by altitude regulations, so they can fly at a minimum of 500 feet above ground level. RC aircraft are free to maneuver at any altitude, giving you the freedom to decide which altitude is best for your aerial photographs.

Not only is RC aerial photography a valid business, it’s also a great hobby. What better way to get aerial pictures of your house, or pictures of your street than with your own RC aircraft?

This article will introduce you to RC aerial photography, show you how to get great aerial pictures, and demonstrate some of the many applications of available technology.

The Basics Explained: Light and Angle

Light is one of the primary factors affecting any aerial photo. Unlike indoor photography where several sources of light are available, RC aerial photography depends entirely on the light provided by the Sun. Use sunlight to your advantage by following these guidelines:

Ground based photography is best done in the morning or evening, because the of the favorable lighting and because shadows are hidden behind the subject. Aerial photography exposes these shadows, so try to take your aerial pictures when the Sun is highest in the sky. This is usually between 10:00 AM and 2:00 PM, but will vary from season to season. Taking aerial photos when the Sun is high will minimize the shadows that appear in your aerial pictures, increasing clarity and reducing “visual clutter”.

There are three main angles or styles from which aerial photos are taken. Each produces a different visual effect, and is used for different applications. They are listed as follows:

1. Vertical – Vertical images are taken with the camera pointing straight down. This is a great angle for surveying, because it gives the photo a scale that you can use to measure the distance between objects. You can calculate the scale of an aerial photo by dividing the focal length of the lens by the altitude of the RC aircraft. For example, an aerial picture taken from a camera with a focal length of 1 inch at an altitude of 50 feet (600 inches) would have a sca1e of 1/600. This means that one inch measured on the image corresponds to 600 inches on the photo. This calculation will work with any units (kilometers, meters, yards etc.) as long as both the focal length of the camera and the height above ground are expressed in the same units. Because the camera refocuses to keep the image sharp, this method will provide only a rough estimate of the scale factor of the image. Fortunately, software is available to calculate and measure distances on aerial photos precisely.
2. Low Oblique – Low oblique photos are taken from an angle of 40 degrees from vertical. They provide a large view of the ground, but don’t show the horizon.
3. High Oblique – High oblique photos are taken at least 70 degrees from vertical, and include the horizon. High Oblique photos will provide a very large overview of an area, and can show varying amounts of sky in the image depending on the angle from the ground.

Atmospheric Effects

There are several atmospheric affects which influence the look of your aerial photos:

1. Haze – Haze is caused by particles and water drops suspended in the air. Haze severely limits the contrast of your pictures, because the light emitted from them had to travel through hundreds of feet of haze before reaching the camera. Haze is most common in metropolitan areas, where there is significant pollution, and during the summer months. Even if atmospheric conditions aren’t perfect, you can minimize their effects on your pictures by shooting with the sun at the back of the camera. This avoids showing haze or smoke in the atmosphere.
2. Clouds – Clouds can also hinder RC aerial photography, by diffusing light and casting large shadows on the ground. In general cumulus clouds (large, low clouds) are the most obscuring, but even thin cirrus (high and wisp like) clouds can cause a loss of lighting. Try to take aerial pictures on days with a minimum amount of cloud cover.
3. Smog – Smog has a similar effect as haze, reducing the clarity of your aerial pictures. Smog is caused by excessive air pollution, and is most common in large cities.

Effects Caused By Motion

Cameras work by letting light hit a photosensitive material for a set amount of time. If the camera or subject are moving relative to one another, then image blurring will occur during the exposure time. By reducing the exposure time (increasing the shutter speed) you can minimize blurring in your aerial photos. You can also minimize image blurring by matching speed and direction with the target.

Planning The Flight

The most important factor that you need to consider when planning an RC aerial photography flight is the weather. As previously discussed, cloud cover will lower available light and reduce the contrast of the aerial pictures. Wind also has an adverse effect on RC aerial photography – creating unwanted motion between the camera and the subject being photographed. Also, RC become difficult to control in high wind conditions, increasing the chances of an accident.

An ideal day for RC aerial photography would be windless, completely clear of clouds, and free of any atmospheric interference (smog, haze etc.) Because this is rarely the case, you will have to listen to weather reports and use your own judgment to determine the best days to fly. There are several excellent sources of weather information available, including radio reports, television, and the internet. You can find weather information and forecasts at the Weather Network and (for Canadian locations) at Navcanada. By clicking on the METAR/TAF button on the Navcanada forecasts and observations page, you can browse frequently updated weather data, used every day by pilots of full scale aircraft. Unless you are familiar with METAR/TAF abbreviations, we suggest that you select plain English forecasts and reports. The METAR is a weather report taken at a current time for a certain location, and the TAF is a forecast predicting the at the location.

Weather reports outside North America can be found on BBC Weather.

Conclusion

RC aerial photography can provide a new perspective on everyday objects and places. New platforms, such as the Tango aircraft (for long range applications) and the Draganflyer X6 open new possibilities for this exciting business and hobby. A full exploration of RC aerial photography is beyond the scope of this article, we suggest reading some of the excellent books on the subject available.