KEYWORDS: Equipment, Long wavelength infrared, Polarimetry, Short wave infrared radiation, Environmental sensing, Army, Sensors, Mid-IR, Imaging systems, RGB color model
The Spectral Polarimetric Instrument Recommendation and Evaluation (SPIRE) project compared the use of spectral and polarimetric instruments for standoff detection and discrimination of explosive hazards in varied environments. Fifteen instruments primarily comprising small fieldable focal plane polarized imagers in the visible, shortwave infrared, and longwave infrared bands were deployed in three kinds of configurations, namely on masts, on ground vehicles, and on an uncrewed aerial system, and collected many terabytes of data in nine field campaigns imaging thousands of targets and natural backgrounds in desert, arctic, temperate green, and tropical environments. In addition to the primary data from these instruments, the SPIRE team collected observations of deployability and operability in these environments as well as other field data including meteorological, radiometric, and other metadata necessary to assess technology performance and ensure robust algorithm development. These data are accumulated on a networked platform for sharing with research and development partners.
KEYWORDS: Polarization, Polarimetry, Long wavelength infrared, Short wave infrared radiation, Cameras, Sensors, Imaging systems, Soil science, Data modeling, Data acquisition
A key product of the global undisturbed/disturbed earth (GUIDE) program is the development of a soils database of broadband, hyperspectral, and polarized data. As a part of the GUIDE program, the U.S. Army Engineer Research and Development Center (ERDC) conducted a testing series involving a large variety of instrumentation at several sites at the Yuma Test Center (YTC) in fiscal year 2015 under the auspices of the Joint Improvised Explosive Device Defeat Organization (now the Joint Improvised-Threat Defeat Agency), generating approximately 17 terabytes of data. Most of this data, available through the ERDC, comprises hyperspectral polarimetric scientific data in the visible, near-infrared, shortwave infrared, and longwave infrared bands. As part of this testing series the performance of six handheld devices was characterized. We discuss the process of this data collection at YTC focusing on the polarimetric data, including the two handheld devices that relied on polarization for detection. Although some other polarization states discriminate soils better in some other wavelengths, for certain visible and near-infrared bands the Stokes S2 parameter provided the best discrimination.
Remote-sensing technology designed to exploit disturbed earth signatures has become extremely useful in the detection of disturbed soil in military areas of operation. Soil reflectance can be exploited for this purpose and is dependent on atmospheric conditions. An understanding of the in situ soil background is vital to any type of change detection. Researchers from the Engineering Research and Development Center (ERDC) conducted OCONUS soil spectral measurements at ten sites in Afghanistan from July to November, 2011. Sampling sites were chosen on the basis of geomorphic setting, surface-soil characteristics, and field-expedient conditions. Goniometric spectral measurements at these sites have provided high quality bi-directional reflectance data, and their analyses are presented in the context of threat recognition and discrimination. These data can also provide the basis for BDRF model validation. Most spectral data were acquired under ambient solar lighting, but other data were collected at night and under artificial illumination conditions. Bidirectional measurements of soil reflectance in the VIS/NIR and SWIR were taken using the University of Lethbridge Goniometer System (ULGS) at dawn, mid-day, dusk and after sunset with a light. Soil surface roughness and reflectance varied, depending on the presence of desert varnish and desert pavement at some sites. Sun angle and dust and smoke in the atmosphere impacted soil reflectance and noise in the SWIR part of the light spectrum, in particular. The presence of minerals such as calcium carbonate, gypsum, and oxidized iron in the subsurface directly impacted reflectance measurements in disturbed soil.
This paper describes the visual, spatial and thermal characteristics, and analysis of dynamic landscape conditions critical to mine detection sensors. The characterization data will be used to develop a geospatial, all-season high fidelity data set to support the modeling of synthetic battlefield environments. Surface and subsurface targets of various materials and sizes were added to natural backgrounds to measure the spectral and thermal changes due to different environmental conditions. The imagery was collected with a four-camera system, each representing the visible near infrared (VNIR), 0.4-1.0 micron spectrum, the near infrared (NIR), 0.9 to 1.7 micron spectrum, the mid-wave infrared (MWIR), 3 to 5 micron spectrum, and the long-wave (LWIR), 8 to 14 micron spectrum. The four imaging systems are mounted on a rotating boom that is raised to approximately 12- meters above ground level to match the nadir aspect airborne imaging systems. Multiple areas within the rotational footprint are selected and measured every 10-minutes through a diurnal cycle. Concurrent meteorological measurements are recorded to identify wind speed and direction, air temperature, surface conditions and relative humidity profiles. The background and target analysis procedure is a process of several steps. First, the regions of interest (ROI's) are selected that identify the target or area to be characterized. Second, the area and statistical values will be calculated for each region of interest. Third, the ROI values are compared to the onsite meteorological station.
This paper describes the high temporal (1 sec to 5 min) and spatial thermal infrared directional characterization of low dense grass canopy during high humidity conditions to study the diurnal and spatial variation of simple vegetation background signatures. The instruments used in the characterization effort consisted of two infrared cameras (8-14 μm) set at nadir and 45 degrees, four sets of radiometers (3-5 μm and 8-12 μm), micrometeorological instruments, and thermocouples placed within the grass. Micrometeorological measurements included wind speed, air temperature, and relative humidity observed at several heights above the canopy sampling occurred at 1 sec and 5 min intervals. These measurements were used to calculate wind speed, air temperature, and relative humidity profiles down to the top of the grass canopy.
Analysis of the measured thermal images consists of quantifying the diurnal thermal differences in the directional background signatures, directional thermal variance, and thermal variance differences related to observation angle, solar radiation, and wind speed. These preliminary analyses indicate that for this environment, measurements at large temporal scales, the thermal variance is primarily affected by solar radiation, but at small temporal scales turbulent mixing of fluxes becomes the more dominant cause of the variance.
The purpose of the Explosives Fate and Transport (EF and T) experiments is to define in detail the accessible trace chemical signature produced by the explosives contained in buried landmines. We intend to determine the partitioning, composition, and quantity of explosive related chemicals which emanate form different kinds of landmines buried in multiple soil types and exposed to various climatic events. We are also developing a computer model that will enable us to predict the composition and quantity of ERC under a much wider range of environmental conditions than we are able to measure experimentally.
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