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Infrared and NDVI Questions

  • What is infrared?

    Infrared is a longer wavelength than visible color. By using a camera that can see infrared, we can take an image of it. Our infrared images can also be color infrared (meaning the green and red channels are also used), making them easier to interpret. Infrared can help show problem areas on fields (like spokes, rings, irrigation leaks, dead areas, etc) more clearly than color. For forestry applications, infrared is often used as a clearer way to do stem counts and type trees.

  • What is NDVI?

    Normalized Difference Vegetation Index, or NDVI, is a vegetation index and is one of the several vegetation indices Eagle uses. NDVI combines the red color and infrared parts of the images together into a ratio. This creates the index.

  • What does NDVI show?

    NDVI, and other vegetation indices, show relative growth vigor, and are primarily used for agriculture. Growth vigor corresponds to the health of the plants. We say that the index is relative because it only shows how well an area of a field is doing compared to the rest of the field at the moment the image is taken. It is not an absolute value, so it cannot be used to compare exactly to other fields or other days. It provides a tool, but does not take human expertise out of the equation.

  • What are some things that show up in NDVI/infrared?

    Many things that affect the health of the plants. This might be over or under watering or fertilizing, a pH imbalance (in sensitive crops like blueberries), insect or pest infestations, disease, and even irrigation system problems like a broken or plugged nozzle.

  • Do all problems on a field show up in an NDVI image?

    No. They will not show everything, and they will not necessarily tell you what the problem is. It can't tell you if there is a pH problem, or if it is a disease. What NDVI can do is tell you that the health and vigor of your plants is compromised. Figuring out the exact cause, and the solution, are still the domain of the local expert (you or your crop advisor). NDVI images are a great tool, but they cannot do everything.

  • What is the difference between NDVI and infrared?

    Infrared images are real pictures of the reflected infrared (like color is a real picture of reflected color). NDVI, on the other hand, is not an image of reality, but a visual representation of a ratio of a color channel plus the infrared channel. This makes NDVI almost closer to a graph or chart than to a photograph. The information is still quite real, but it is determined through formulas, not through reflected wavelengths.

Technical Questions

  • How high do you fly?

    It depends on the resolution and application. We fly anywhere from 1500 to 15,000 feet above the ground. Our flights are high enough that people on the ground are not aware of us.

  • What kind of aircraft do you use?

    We deploy both manned and unmanned platforms depending on the mission profile. Our goal is to provide the customer with the most cost effective solution while insuring the highest level of safety.

    Our manned aircraft fleet include multiple models of Mooneys which are highly efficient, single pilot, high performance aircraft. Models that we own include the 300 hp turbo charged Rocket conversion as well as the factory turbo charged Mooney Bravo.

    Part 107 of the FAA regulations and our FAA exemption for flying drones allow us to fly a broad range of different unmanned aircraft. We currently fly the DJI S900 unmanned aircraft system because of it's configurability, payload and easy of use.

  • What kind of cameras do you use? And why?

    We use Canon Professional Digital SLR cameras. We are currently using the Canon 5D Mk II camera with 21 megapixels and the 5DSR with 50 megapixels. The cameras gather images at 14-bits per pixel and this is then converted to the desired output format (usually 24-bit RGB). They have a dynamic range that is excellent. Canon creates the best DSLR cameras in the world. Image quality is very important to us and these cameras really do deliver. We start with the Canon camera and then build it into our camera system. It is surrounded by a ¼ inch stainless steel chassis to maintain its internal orientation and alignment with the GPS and IMU (inertial measurement unit).

    We use a separate camera for infrared. We then use multi-modal image alignment software to create the color IR images and to ensure that they line up with the color images.

  • What about digital vs. film aerial images?

    There is a reason that nearly all professional and artistic photographers have moved from film to the Canon digital cameras, and the cameras keep improving. Film use in aerial photography still has its place, mostly for adhering to old mapping, because a company wants to maintain a similar workflow and needs the 9 X 9 print format, or because an old specification is being used.

  • How high is the resolution?

    This varies substantially. We are able to do resolution as high as 1 inch, but this is not always practical. For agriculture, most of our images are taken between ¼ to 1 meter ground sample distance. For forestry, it is generally about 2 feet. We use the optimum point between cost effective images and resolution: enough to see what is going on, but not more. We are very flexible and fly at many resolutions, so we will always discuss resolution options with you during planning.

  • What projections can you do?

    All of the standard projections. We have never encountered a projection we cannot do, in fact, so just ask!

  • Why do you have a minimum sun angle requirement, and what is it?

    We always set a minimum sun angle for our projects, that is usually around 45 degrees for forestry (sun angle is less of a problem for agriculture). The reason for this requirement is that images taken in the morning and evening, when the sun is lower than 45 degrees, are not of the same high quality. A high sun angle means that the light is consistent throughout the images, and, more importantly, that the shadows are minimized so you can see everything you need to see. Our sun angle requirement is essentially a self-imposed quality check that ensures we are consistently delivering the highest quality images possible, even though it means we can only take images for a certain portion of the day.

    We could extend our flying time but our commitment to quality does not allow us to acquire and deliver inferior images. Although we generally take our images with appropriate sun angles, this is to increase quality, not because our cameras require it: our cameras are excellent at lower light images. We often take images in the northwest in the dead of winter (the sun angle requirement must be adjusted). In most cases our cameras operate with a faster shutter than other systems. This allows us to use an aperture setting that takes advantage of the sharpest lens settings. A wide open lens will usually create more distortion. Also, the 14-bit dynamic range of our images provides excellent dynamic range. Even if shadows exist, our system can often see into them. This is how we are able to deliver winter images.

  • What kind of processing goes on after images are taken?

    A lot more than you might think. Images are orthorectified (a process that converts the 3D world into 2D) and georeferenced (this means adding information to the image that tells programs like GIS software where the image is located on the earth). Also, the color of images is adjusted slightly to be realistic and consistent, and multiple images may need to be mosaiced together. This intensive process takes several hours of work by skilled processing technicians.

  • How does your image quality stack up?

    We have been evaluated by many customers, both private companies and government agencies, regarding the horizontal position accuracy of our images. In each case we have met or exceeded their accuracy requirements.

    We have also been evaluated for image quality and again have met or exceeded other options. We do not use a fully automated approach to image adjustments. We use automation where it makes sense and we use humans where the computer falls short. Adjustments to compensate for atmospheric turbidity (changes in color due to changes in the atmosphere) are best done by experienced processing technicians. Our color quality is one of the major advantages of using the Canon cameras.

    You will also have input into this process. We have found that certain companies are used to a particular color bias. In those cases, we use reference images to best match their requirement. This does not happen very often as our standard true color images are usually the best option.

  • You don't use ground control points: are your images really orthorectified?

    Our images are orthorectified. It is important to ensure that you are getting true orthorectified images. In traditional photogrammetry, ground control targets are used to determine the external orientation of the image. This is the accurate location of the camera and where it was pointing at the time of exposure. By knowing the location of the ground control points and where those same ground control point targets are located on the image, the external orientation can be determined.

    Our system uses a very accurate GPS (a few centimeters with post processing) and a very accurate IMU (inertial measurement unit). The GPS provides the location and the IMU (in conjunction with the GPS) provide the direction.

    These data are then processed to create accurate external orientation. The external orientation is used along with the camera calibration data and the best available DEM to produce the orthorectified image. We use the Leica Photogrammetry Suite from ERDAS for orthorectification.

  • What is workflow integration and how does it work?

    Workflow integration is something that sets Eagle apart and makes it easy for you to actually use our images. Instead of just sending images, we put time into assessing your data and work flow. We accept data from you in the form you already use, so you don't have to change that. Then, we find out what type of data will work best for you, and we deliver data in that form. Beyond this, we work with you to customize our process so it really fits what you are doing. This may mean keeping track of all of your fields and creating an imaging rotation system for you, or even flagging images of fields that have significant change from the last image so you can quickly look at high priority areas. Whatever it is you are doing with the images, we can make your life a little easier, so the images come in seamlessly and you can just get right to work.

  • Where can I get more info?

    Please contact us so that we can answer your additional questions directly.

Ordering Questions

  • Where do you fly?

    We are a custom data generator and information provider having completed projects from the Canadian border to central California and from the Pacific Ocean to Minnesota. With four aircraft we can take on projects anywhere in the continental United States. The map below shows actual projects that we have completed over the last few years. Each colored area shows the extent of a given project. The top of the map is the Canadian border and the right most section is western Montana. Note that the inset box in the lower right corner is a recent project in Minnesota.

    Map of imaging projects

  • How much does it cost?

    Please contact us for pricing information. We do not list our prices because there are so many variables (the size of the project, what processing is needed, what resolution is required, etc) that it is very difficult for us to provide a general price estimate without your specific requirements. We are happy to explore all of the pricing options with you, however, so please do call or email. We do not list prices online because so many factors are included, not because it is so expensive that if you have to ask, you can't afford it! It is much more economical than you might think, so please give us some information about your project so we can give you an idea of pricing.

  • How long does it take to get images?

    Our turnaround time varies significantly based on the type and scope of the project. We are typically faster than other vendors, however, due to our custom processes. Our typical delivery time is anywhere from a couple days to a couple weeks.

  • How can we order images?

    Contact Eagle by phone or email. We will discuss options and pricing with you. Then you will receive a proposal with all of the image details. When everything is worked out, we will fly the area as soon as weather and scheduling permit, and processing will begin immediately. We will keep you updated on the status of the images. When they are ready, you will receive them on a DVD or hard drive, and/or in poster or print form.

  • How big an area do I have to buy?

    Since we own our own planes and equipment, all of our flights are custom. You may order as small or large an area as you want: no need to pay for an entire county when you only want images of a field or harvest unit! Our software allows us to be efficient when planning flights to image scattered sites, so please let us know exactly which areas you need to save us time and you money! Keep in mind that the cost per acre is less when you order a larger area.

  • Can you fly all year?

    Theoretically yes, but as we all know the unpredictability of the weather, there are some definite limitations. We are usually unable to take images on bad weather days (unless the clouds are very high and even), so we have to wait for clear skies. Also, shadows are longer in the winter, which may make images less ideal for some applications. The short answer is yes, weather permitting (although it's certainly easier in drier areas!).

  • How could I make it cheaper?

    If you need images in a broader time frame (a month, say, instead of on a particular day), we may be able to keep your data in the system and wait to fly it until it fits well in our schedule and can be combined with another project. Since the flight would not be only for your images, the operating costs (and thus the costs to you) can go down. Also, getting lower-resolution images is an option we can explore, but we want to make sure the images are high enough resolution that you can see what you need to see.