What is the difference between a rolling shutter and a global shutter camera?
When planning a drone flight for precision farming choosing the best multi-spectral sensor for your job is essential therefore knowing the main differences in terms of camera features becomes fundamental. We would like to start from the differences between the rolling shutter and the global (or frame) shutter.
Some types of image sensors provide an electronic shutter mechanism known as a global shutter. In imagers that use a global shutter the pixels accumulate charge for some period of time, with the light collection starting and ending at exactly the same time for all pixels. At the end of the integration period (time during which light is collected), all charges are simultaneously transferred to light shielded areas of the sensor. The light shield prevents further accumulation of charge during the readout process. This means that with a global shutter sensor, the scene will be “frozen” in time and that is there is no motion blur. This said when integrated on UAVs the main advantage of a global shutter camera is the speed at which we can fly with no blurr effect as the camera as integration time is immediate. Consequently by flying faster the coverage area increases enabling us to cover more extended areas.
With the rolling shutter, pixels do not collect light at the same time. All the pixels in one row of the imager collect light during exactly the same period of time, but the time that light collection starts and ends is slightly different for each row. The top row of the imager is the first one to start collecting the light and is the first one to finish collecting. The start and end of the light collection for each following row is slightly delayed. The time delay between a row being reset and a row being read is the integration time. In relation to camera usage with a drone, since the integration process moves through the image over some length of time, users should keep in mind the fact that when working with rolling shutter sensors in flight at a higher speed,there will be a blur effect due to the integration time (time needed to freeze the scene). To sum up during image acquisition whilst flying a UAV global shutter cameras allow a higher speed as there is no blurriness. For obvious reasons ther are preferred in surveying large extensions where more speed is requested.
NB: the distance from the surveyed object/area and the lighting condition must always be kept in mind.
How does the multi-spectral drone work?
Analist Group provides all the necessary info when it comes to camera/sensor best choice and usage, most suitable drone for the application requested and not only. Fly, generate NDVI maps and DTMs.
- Fly and acquire your imagery (set the flight plan and frames per second: your DRONE will do all the work).
- Import the images into Pix4Dmapper to automatically create NDVI Maps, Point Clouds and Digital Terrain Models (DTMs).
- Import the Point Cloud into Analist 2016 CLOUD and create Profiles, Cross Sections, Contour Lines, Areas and Volume calculations and much more.
- Last but not least animate your 3D Model with OneRay-RT. Only Analist Group can offer you the Complete Professional Solution for Precision Farming.
Analist Group Multi-spectral Drone Solutions for Precision Farming.
Interested in more info on the Tetracam camera for precision Farming? Analist Group Multi-spectral Drone
Another important aspect to consider when choosing the best tool for your application is the type of imager: multi-imager or single-imager?
Given that Multispectral cameras work by imaging different wavelengths of light, a single-imager multispectral camera uses a blocking filter, combined with the standard camera’s built-in filter to capture information in 3 wavelengths of light. Because these imagers aren’t optimized for remote sensing, the built-in filters are wideband and suffer from data contamination from neighboring bands. This figure shows a comparison of the RedEdge™ narrowband optical filters and the filters used in a typical single-imager camera.
Analist Group is Official Parter to MicaSense. Images and contents courtesy of MicaSense