WHAT IS THE DIFFERENCE BETWEEN 30 HZ AND 9 HZ?
Las cámaras de vídeo emiten una serie de imágenes «fijas» a un ritmo regular, un ritmo dado en hercios (Hz) o en fotogramas por segundo (fps). Las cámaras UAS de FLIR con vídeo de 25 a 60 fps emiten ese número de fotogramas únicos por segundo. Para facilitar el transporte de las cámaras a través de las fronteras, existe una clase de cámaras «<9 Hz". Estas cámaras envían fotogramas de vídeo a una velocidad normal, pero estos fotogramas se duplican durante intervalos cortos. El resultado es una frecuencia de imagen efectiva inferior a 9 fps. Póngase en contacto con un especialista en exportación antes de transportar cualquier cámara térmica de un país a otro.
CAN I EXPORT OR TRAVEL INTERNATIONALLY WITH MY THERMAL CAMERA?
There are international regulations on the transport and movement of all thermal cameras. Export laws allow thermal cameras with frame rates below 9 frames per second (fps) to move more freely across borders than 60 or 30 fps cameras. Contact an export specialist for more details.
WHAT IS THE DIFFERENCE BETWEEN 160 × 120, 336 × 256 AND 640 × 512 RESOLUTION CAMERAS?
Each FLIR UAS thermal camera has an imaging device known as a focal plane that converts the target image into pixels. The sizes 160 × 120, 336 × 256 and 640 × 512 are examples of the resolution options available for these cameras. The first value represents the number of horizontal pixels and the second number represents the number of vertical pixels. At first glance, many people assume that the 640 has twice the resolution of the 336, but in reality the total number of pixels is 3.8 times greater. The 336 × 256 offers 86,016 total pixels and the 640 × 512 offers 327,680 pixels.
WHAT IS THE FIELD OF VIEW?
The field of view, also referred to as FOV, is the degree of visibility that the camera lens provides to the sensor. For example, each pixel in the 640 × 512, 13 mm configuration (45 × 37 degree FOV) will represent an angle of 0.07 degrees per pixel, which means that at 30.5m, each pixel is imaging 4cm. From a less technical point of view, FOV equals the observable area that can be imaged with the lens. The graphs below show how various FOVs on 640 and 256 cameras correspond to the observable area when looking down. The calculation is linear, so an elevation of 60 meters would double the value, while an elevation of 50 feet would be half the value.
WHAT IS THE BEST LENS FOR MY CASE?
There are two main considerations in determining the best lens and resolution for a given application. First, the field of view (FOV) is the approximate angle of the observable image. Figure 2 shows the observable area per lens model at 30.5 meters (100ft) AGL assuming you are looking straight down.
The second factor is the angle that each pixel represents, known as iFOV. Knowing the angle of each pixel helps to calculate the number of pixels that would appear for various targets at different distances. For temperature measurement, an object should appear at least in a 5 × 5 pixel grid, but 10 × 10 or more will give even better results. The target should be chosen so that the FOV is wide enough to find what you are looking for, and that the iFOV allows enough "pixels on target" at the desired flight altitude.
Figure 2 shows the spot size at 30.5 meter AGL when looking down. Worldwide, the 640 × 512, 13 mm option is the number 1 selling model and performs most tasks very well.
*AGL(Above Ground Level) = Above ground level
WHAT SHOULD I BUY?
Camera systems are usually available as a package with a compatible drone. This is the easiest way to ensure compatibility. There are gimbal packages available that target specific cameras on specific drones or drone families. They may be available through the vehicle manufacturer or third parties. The documentation for each stabilizer will identify the cameras and vehicles with which it is compatible.
To integrate a general-purpose sUAS camera into your existing drone, a number of factors need to be considered.
Weight and center of gravity (CG): The drone must be able to lift the camera and still maintain a useful flight time. Some measures need to be taken to support the camera on the vehicle and maintain balance. FLIR UAS cameras typically have a ¼-20 threaded hole on the top, bottom, or both sides of the camera. These holes are the same size and thread pattern found on consumer cameras, so they can be used on tripods.
Power supply: Most FLIR cameras are designed to draw power directly from the vehicle battery, while others draw regulated 5 volts from a battery elimination circuit (BEC). The voltage and current requirements for each camera can be found in the camera's data sheet or user's guide.
Video: The camera may have HDMI or composite video outputs. If real-time video is required for your mission, a compatible video downlink system must be provided.
Camera and stabilizer control: Various features of the camera and any associated gimbal will need to be controlled. Often, this is done using PWM servo signals. These are three-pin outputs from the flight controller or remote control receiver that are used to control motor controllers, servo actuators and other vehicle components.
GPS: Some cameras have built-in GPS receivers to geotag image files. These receivers may need to be connected to external antennas, which are usually placed on top of the vehicle to get the best possible satellite reception. Some cameras do not have internal GPS receivers, and if the image files are to be geotagged, the GPS information from the vehicle will have to be sent to the camera. Typically, this will be done using MAVLink. The engineering data sheet or user's guide will list the available interfaces and their capabilities.
CAN I DETECT METHANE GAS LEAKS WITH MY THERMAL CAMERA?
IR gas detection cameras work by detecting the absorption of light or thermal energy by gases. This absorption is usually weak and in a narrow spectrum, so specialized optical filters and high quality sensors are required. General purpose thermal cameras do not detect these gases reliably. Gas detection chambers are specially designed with narrow optical filters and usually contain a cryogenic cooler, which consumes additional power and adds weight. Take a look at gas detection chambers here: OGI chambers.
HOW HIGH CAN I FLY WITH MY THERMAL CAMERA?
The maximum allowable altitude can be found in the environmental specifications of the product data sheet.
Although typically 11,500 meters MSL for most products, UAS vehicles must be operated in accordance with applicable laws. In addition, camera resolution imposes practical limitations on useful altitudes. At an altitude of120 meters, one pixel on a VUE Pro R camera with a 13 mm lens would represent an area more than 6 centimeters wide. For most thermal imaging applications, the lens would have to be much closer to provide enough pixels on the lens to make the image useful, or a camera with a different lens must be used. For example, at the same altitude of 400 feet (120 meters) and with a 25 mm lens, one pixel would represent an area ~3.4 inches (8.6 cm) in diameter. To measure temperature, an object must appear as at least a 5 × 5 pixel object in the image. Even better results are obtained with 10 × 10.
* MSL (Mean Sea Level) = Above sea level
HOW FAR CAN I SEE DEPENDING ON THE OBJECTIVE CHOSEN?
There is no practical limit to how far a thermal camera can see through a clear line of sight, but it is important to understand what you are looking at. The moon is usually visible when it is not obscured by clouds (water vapor absorbs IR energy). Viewed from Earth, the moon subtends an angle of about 0.5 degrees, so in a 25-degree FOV, 640-resolution camera, the moon would appear as a circle about 12 pixels wide.
The normal limit for the target distance of an IR camera is the size in pixels that the object will appear in the image and the number of pixels required to identify or extract the necessary information about the target. For example, as shown in the image, do you want to detect, recognize or identify the person in the image? The number of pixels you place on an item allows you to make the determination. To measure temperature, an object must appear as at least a 5 × 5 pixel object in the image. With 10 × 10 you get even better results.
CAN I CREATE 3D ORTHOMOSAICS WITH MY THERMAL DATA SETS?
FLIR does not currently offer tools to create thermal orthomosaics. For mapping operations, third-party thermal orthomosaic services with expertise in thermal camera image processing are available. Currently, the ability to retain radiometric temperature data at the pixel level is lost in the orthomosaic creation process.
WHICH SOFTWARE IS BEST FOR MY THERMAL DATA SET OR MY OPERATION?
Different cameras offer different file types and features. In addition, different applications have different requirements. Higher resolution thermal cameras (320 × 256 or more) can achieve a better level of detail by saving the images in the -R.JPEG format and processing them with the free FLIR Thermal Studio Starter application. This combination allows post-flight adjustment of radiometric parameters and provides a simple framework for generating reports. CSV files of the pixel values can also be created for further processing. FLIR Thermal Studio offers batch processing for jobs requiring a large number of files.
WHICH STABILIZER SHOULD I USE FOR MY VUE PRO R?
FLIR does not have specific recommendations for Gimbals. Third party stabilizer suppliers will have information on the compatibility of their products.
HOW DO I GET VIDEO STREAMING FROM MY CAMERA?
For real-time video streaming, FLIR's UAS cameras provide NTSC/PAL composite or HDMI video. Check the camera data sheets to see which video output formats are supported by third-party downlink systems.
WHAT IS RADIOMETRY, DO I NEED IT?
Radiometry is the measurement of the amount of radiation coming from a target, usually in terms of target temperature. This function is not always necessary for a given application. Radiometry is only available in high quality thermal cameras. Thermal images usually provide information that can be easily interpreted by the user. For example, when a solar panel appears noticeably cooler than its neighbors or has a more uneven temperature than its neighbors, it is not necessary to know the magnitude of the difference in degrees: check that solar panel. Similarly, when one vehicle shows hot brakes and a warm engine, while others do not, it is clear which vehicle was last on the road without needing to know the actual temperatures. When a suspicious person is spotted hiding in vegetation, it is not necessary to know their body temperature. Many thermal imaging applications can be performed in this way without the need to measure absolute temperature. In some cases, an absolute measurement is necessary. For example, when checking a transformer on a power pole, there may be no nearby transformers to compare. For applications such as this, a radiometric camera would be used, and the estimated surface temperature would be compared to established limits.
WHICH COLOR PALETTE IS BEST FOR MY JOB?
Many thermal camera users in laboratories or in the military use the White Hot/Black Hot palette. Exaggerated color palettes can be used to highlight temperature changes that might otherwise be difficult to see, but they make additional noise appear and can mask key information. Color palettes should be chosen to show the relevant details of an image without distraction. If FLIR's R.JPEG radiometric image file format is used, the color palette can be changed after a flight using the free FLIR Thermal Studio application or the Pro version.
WHEN SHOULD I USE ISOTHERMS?
The isotherm function highlights a range of temperatures with a color change. This can facilitate finding objects of a known temperature against a background of a different temperature or to highlight areas of a field that have exceeded a certain temperature. Isotherm is only offered in radiometric cameras. The accuracy of the isotherm function is the same as that of the temperature measurement.
HOW ACCURATE IS THE TEMPERATURE READING?
Hay dos elementos a tener en cuenta en relación con la temperatura: la sensibilidad térmica y la precisión de la medición. La sensibilidad térmica es la capacidad de la cámara para detectar diferencias de temperatura. La mayoría de los sensores IR no refrigerados en las operaciones de los UAS tienen una sensibilidad térmica de <50 mK.
The accuracy of the temperature measurement varies depending on the selected range. For example:
+/- 5 °C or 5% of the readings in the range of -25 °C to +135 °C
+/- 20 °C or 20% of the readings in the range -40 °C to +550 °C
Radiometric parameters are environmental details that affect the amount of thermal radiation emitted by an object or that affect the amount of radiation reaching the camera. For example, for a given surface temperature, an object with an emissivity of 48% will emit half as much thermal radiation as an object with an emissivity of 96%. Objects with lower emissivity will also reflect more thermal radiation from their surroundings. For this reason, emissivity and background temperature must be known and considered for an accurate estimate of an object's temperature. Long distances or atmospheric attenuations will affect the amount of thermal radiation the camera will receive from an object. These parameters can be adjusted on the camera for real-time viewing. If FLIR's R.JPEG radiometric image file format is used, these parameters can be further adjusted using the free FLIR Tools or FLIR Thermal Studio Pro application.
DO I NEED SPECIAL TRAINING TO OPERATE A THERMAL CAMERA?
For many uses of thermal cameras, the information presented is so intuitive that little or no training is needed to get results. There are free videos on FLIR Delta and other FLIR websites that can be used to get started. More experienced operators will get even more out of thermal imaging. Some applications require formal training and certification for quick and consistent collection and interpretation of thermal data. At Apliter Termografia we offer complete training and certification services from the Infrared Training Center. Check this page to see the courses we offer: https://itc.apliter.com/
WHAT IS THE MINIMUM AND MAXIMUM TEMPERATURE RANGE OF THE CHAMBER?
Camera specifications can be found in the individual product data sheet. The VUE Pro R can reliably measure temperatures from -25 °C to 135 °C, but can also detect targets from -40 °C to 550 °C with reduced accuracy and sensitivity. Objects outside these ranges will appear as solid, light or dark regions with no surface detail.
ARE MY THERMAL IMAGES AUTOMATICALLY GEOTAGGED?
If the camera has GPS data, images stored in FLIR's radiometric R.JPEG format will be geotagged. Thermal images in TIFF format will also be geotagged, but since there is no official geotagging format in TIFF 6.0 format, the tags used may not be readable by all programs. The geotag information for video files is stored in an SRT file with the time of day. Many video viewing programs can view the SRT file data as subtitles.
Some FLIR UAS cameras have a built-in GPS receiver. If that receiver has GPS lock, the location data will be stored. If there is no GPS receiver in the camera, the files can still be geotagged if the location data is sent by the vehicle to the camera via MAVlink.
WHAT CAUSES HALOING OR VIGNETTING IN MY IMAGES?
Thermal cameras work best when all camera components are at the same temperature. In a drone camera, this is almost never the case. Heat from the electronics and stabilizer motors inside the housing reaches one end of the camera, while the lens is cooled by the propeller slipstream. This often results in the outer edge and corners of the image appearing cooler than the center. This "image non-uniformity" is often described as vignetting, haloing or, if one of the more extreme color palettes is applied, a "purple ring". The camera compensates for this to some extent, but the dynamic nature of the problem makes it difficult to completely avoid the effect.
HOW CAN I REDUCE HALO OR VIGNETTING EFFECTS IN MY IMAGES?
All thermal cameras have some image non-uniformity. This often takes the form of cooler edges and corners, causing a halo effect. The most extreme color palettes available in your camera are created to exaggerate any detail in the image. A low contrast scene has less detail, so the colors will be applied to noise or other artifacts. In most cases, it is easier to interpret thermal images with the Black Hot, White Hot palette, as these show more consistent contrast. Also, scenes with people or other warm objects will "stretch" the colors, making the halo less noticeable.
HOW CAN I CONVERT PIXEL DATA TO TEMPERATURE?
Only pixel values from radiometric thermal cameras such as FLIR Vue Pro R or TZ20-R can be converted to temperature values. For these cameras, the pixel values in the tiff file have already been converted to a temperature based on the emissivity of the lens, the background temperature and other radiometric parameters present in the camera at the time the image was taken. These values are stored with a scale factor. To convert them to degrees Kelvin, they must be multiplied by 0.04 (if the camera was in high gain mode) or by 0.4 (if the camera was in low gain mode). High gain is the default mode and low gain is only entered when temperatures exceed 135° C. To convert from Kelvin to degrees Celsius, subtract 273.15 from the Kelvin value. For example, a pixel value from the tiff file of 7500 (decimal) 7500*0.04 - 273.15 is approximately 27 °C.
FLIR's R.JPEG radiometric files are more flexible than tiff files. R.JPEG files can be opened with FLIR tools and the radiometric parameters can be set to different values for post-flight corrections. This allows estimating temperature values for different targets with different emissivity values, or adding values not known at the time of the flight. Various point and area meters available in FLIR Thermal Studio can be used interactively to analyze the image.
To create a CSV file with all pixel temperature values of an R.JPEG file, open the file in FLIR Thermal Studio, make the necessary radiometric parameter settings, and then export via the menu the file to CSV. You can choose to create a CSV file for the entire image or for any point or measurement area you have created in the image.
MY MOBILE DEVICE DOES NOT CONNECT TO THE CAMERA. WHAT CAN I DO?
The FLIR UAS application requires access to the camera's Bluetooth transceiver. It is possible that various security or battery saving plug-ins and protocols may interfere with this. The application settings should be checked to ensure that the application has the required access. Bluetooth settings should be checked to confirm that the smartphone transceiver is enabled. Uninstalling and reinstalling the application may reset the correct permissions. Turning the mobile device completely off and then back on again is another thing that may help in some cases.
Strong transmitters, such as video downlinks, telemetry or remote controls, can affect the phone's transceiver, even if they do not operate in the same band. Trying different locations for the smartphone may help. If done safely, turning off unnecessary transmitters can help resolve problems.
Finally, FLIR UAS cameras turn off their Bluetooth transceivers if there is no Bluetooth activity for several minutes. The Bluetooth LED will illuminate blue when activated. To reactivate it, press the Bluetooth button on the camera until the LED turns blue again.
CAN I CHANGE THE LENS OF MY THERMAL CAMERA?
It is not recommended and will void the camera warranty. Removing the lens from a thermal camera exposes the detector window to dust and other airborne contaminants and debris from the lens threads. Any dust particles on this window will create a defect in the image. The window coatings are too delicate to be cleaned.
WHY DOES THE IMAGE SOMETIMES SEEM TO "FREEZE" BEFORE RETURNING TO NORMAL OPERATION?
IR cameras perform non-uniform correction (NUC) before adjusting the level and range. This automatically corrects for the small detector drift that occurs as the scene and environment change. The camera will also perform this operation on its own from time to time. Think of this as an adjustment of all pixels to a base reference point.
If you have any doubts or questions, please contact us.