Omar El Gawhary, Marijn van Veghel, Pepijn Kenter, Natasja van der Leden, Paul Dekker, Elena Revtova, Maurice Heemskerk, André Trarbach, Ramon Vink, Dominic Doyle
We present a portable traceability solution for the ground-based optical calibration of earth observation (EO) instruments. Currently, traceability for this type of calibration is typically based on spectral irradiance sources (e.g. FEL lamps) calibrated at a national metrology institute (NMI). Disadvantages of this source-based traceability are the inflexibility in operating conditions of the source, which are limited to the settings used during calibration at the NMI, and the susceptibility to aging, which requires frequent recalibrations, and which cannot be easily checked on-site. The detector-based traceability solution presented in this work uses a portable filter radiometer to calibrate light sources onsite, immediately before and after, or even during instrument calibration. The filter radiometer itself is traceable to the primary standard of radiometry in the Netherlands. We will discuss the design and realization, calibration and performance verification.
Moving imagery from a static scene was recorded with an uncooled thermal imager at nine different angular velocities ranging from 0 (static) to 1 pixel/frame (3.75 deg/s) using a tilted rotating mirror. The scene contained a thermal acuity test chart with triangular test patterns based on the triangle orientation discrimination (TOD) test method. The imagery was processed with different types of image enhancement: dynamic super-resolution (DSR), local adaptive contrast enhancement (LACE), and combinations. DSR shows a significant performance improvement at low velocities, a moderate improvement at medium velocities where smear becomes apparent, and no benefit at high speed. Performance with LACE is close to optimized gain and level setting by hand. Static performance and dynamic performance at 0.57 pixel/frame containing significant smear were compared with earlier published identification performance data for two-hand held systems collected under a variety of signal processing conditions. It shows that the ratio M75 between the 75% correct threshold size for the two-hand held objects and the TOD triangle is preserved under all conditions measured. Thus, TA range prediction based on the TOD is robust against a complex combination of conditions, including motion, smear, and the types of image enhancement applied.
Moving imagery from a static scene was recorded with an un-cooled thermal imager at nine different angular velocities
ranging from 0 (static) to 1 pixel/frame (3.75 deg/s) using a tilted rotating mirror. The scene contained a thermal acuity
test chart with triangular test patterns based on the Triangle Orientation Discrimination (TOD) test method. The imagery
was processed with different types of image enhancement: DSR (Dynamic Super Resolution), LACE (Local Adaptive
Contrast Enhancement) and combinations. DSR shows a significant performance improvement at low velocities, a
moderate improvement at medium velocities where smear becomes apparent and no benefit at high speed. Performance
with LACE is close to optimized gain and level setting by hand. Static performance and dynamic performance at 0.57
pixel/frame containing significant smear were compared with earlier published identification performance data for twohand
held systems collected under a variety of signal processing conditions. It shows that the ratio M75 between the
75% correct threshold size for the two-hand held objects and the TOD triangle is preserved under all conditions
measured. Thus, TA range prediction based on the TOD is robust against a complex combination of conditions,
including motion, smear and the types of image enhancement applied.
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