| Common to all ITRES imaging sensor products is flexibility in flight planning. Not only can you choose where and when you collect data, but also what the spatial resolution of the data will be. Varying the flying height, aircraft speed, or frame rates influence pixel resolution. Being able to do so provides operational flexibility to acquire data under different environmental conditions to accommodate seasonal or daily solar and atmospheric conditions while maintaining high signal levels. With our VNIR CASI sensor products, you also have the flexibility to spectrally configure these sensors for a variable number of spectral channels and imaging swath widths. A commonly asked question about our sensors is what kind of data resolutions can be expected from a specific sensor. Being pushbroom imagers, all ITRES sensors define pixel resolution in two dimensions: along-track (parallel to the direction of flight), and across-track (orthogonal to the flight direction). Both dimensions are influenced by different flight planning variables.
Frame Time versus Integration Time It is important to note how the CASI sensor line treats the concept of integration time (IT) and frame time (FT) as compared to the our other sensors. With the CASI, owing to its detector array and readout system, both values are considered to be the same. The integration time is programmable by the user. Integration time represents the time (in ms) needed to readout and record a single scan line of data. Because the CASI spectral configuration is programmable (the user can choose the number, placement, and spectral width of each band to be acquired), the more spectral information recorded, the longer the time needed to readout and record each scan line. Conversely, both frame time and integration time are treated as separate variables for our other sensor products (SASI, TASI, and TABI). For these, the frame time and aircraft speed affects along-track pixel resolution, while the integration time affects signal level. Because frame times are fixed with these sensors, the sensor operator need only adjust the aircraft speed to change the acquired along-track pixel size. Should signal levels be too high or low during data collection, changing the integration time can be done to make any necessary adjustments. Along-Track Pixel Resolution The general relationship between the number of spectral bands acquired for the CASI and the time required to do so can be seen in the first two columns of the along-track resolution table below. The longer the integration time for a given aircraft speed, the longer the along-track pixel size (since the aircraft tracks over a longer ground distance during a single “exposure”).  Fix the IT at, say, 13ms (the minimum time needed to record 32 VNIR bands with the CASI-1500), and follow the row across in this table and see how decreasing the operational ground speed leads to shorter along-track pixel sizes. Note that the number of bands and their placement/widths are fixed for the SASI, TASI, and TABI sensors. This is indicated by the boxed row of along-track pixel values seen in the along-track resolution table. Across-Track Pixel Resolution The table seen on the second page of the product sheet download shows the relationship between across-track pixel resolution and flying height for each of our sensor products. Please note that the listed flying heights (in both meters and feet) are measured above ground level (AGL).  |
 Sample Mission Planning Tables |
