Comparison of Stationary and Moving Infrared Thermometer Measurements Aboard a Center Pivot

Abstract

HighlightsStationary and moving infrared thermometers aboard a center pivot were compared.Comparisons were in terms of directional brightness temperature discrepancies.Discrepancies were within 1.8°C, and many were within 1.0°C.Larger discrepancies tended to occur for sparser vegetation cover.Abstract. Infrared thermometers (IRTs) can measure canopy temperature, which is useful for irrigation and crop management. Center pivot and lateral move irrigation systems are suitable platforms to transport IRTs across cropped fields at regular intervals. IRTs aboard center pivots, when used in conjunction with irrigation scheduling algorithms, have resulted in crop yield and crop water productivity that is equivalent to or greater than what can be achieved using soil water measurements of the root zone profile with a field-calibrated neutron probe. Irrigation scheduling algorithms perform best when stationary IRT measurements are supplemented with moving IRT arrays, where the former provides time series data and the latter provides spatially distributed data. However, the normal deflection of moving irrigation systems and other confounding factors have caused concern that moving IRT measurements may be degraded relative to stationary IRT measurements. Directional brightness temperatures (TB) measured by stationary and moving IRTs were compared over two corn and one potato season at the USDA Agricultural Research Service, Bushland, Texas. Moving and stationary TB were compared in terms of root mean square error, mean absolute error, and mean bias error, and were all < 1.8°C, and many were < 1.0°C, and r2 = 0.95. Error terms tended to be larger for potato, which had less vegetation cover compared with corn. However, error terms were similar to previous studies of calibration and spatial variability for IRTs and thermal imagers. Therefore, TB measurements of moving IRTs did not appear to be degraded relative to TB measurements of stationary IRTs for this study. However, interpretation of stationary and moving IRT measurements may be aided by addition of low cost imagers to distinguish vegetation from soil background. Keywords: Canopy temperature, Crop management, Evapotranspiration, Irrigation, Remote sensing, Sensors.

Theory and Development of a VRI Decision Support System: The USDA-ARS ISSCADA Approach

“…Using a calibrated black body in a temperature-controlled environmental chamber, tests done after field deployment showed this system to remain accurate after field deployment (Colaizzi et al, 2018) and thus reusable over multiple years, a result borne out by later experience. The system was demonstrated to be effective and accurate both when mounted in fixed positions in the field and when mounted on a moving center pivot lateral with minimal error due to sensor motion (Colaizzi et al, 2019). Dynamax sells the SapIP-IRT in wireless and cabled (SDI-12) versions nationally and internationally.…”

Targeted, Precision Irrigation for Moving Platforms: Selected Papers from a Center Pivot Technology Transfer Effort

“…Site-specific VRI was identified as an important emerging topic in the U.S. in the 2017 CP technology brainstorming retreat discussed earlier (table 1), and the consensus was that hardware development has often outpaced the development of management information. Special Collection articles addressing site-specific VRI for CP systems and associated sensors for monitoring and/or control are provided by Colaizzi et al (2019), O'Shaughnessy et al (2019a, and Stone et al (2019).…”

“…Inherent to successful VRI application is the ability to monitor crop status in real-time or near real-time to allow dynamic updating of prescriptive irrigation schemes. In a Special Collection article by Colaizzi et al (2019), a comparison of stationary and moving (i.e., onboard CP) infrared thermometer (IRT) measurements is discussed. The authors found that temperature measurement errors and noise were generally similar between moving and stationary platforms and that addition of more expensive hardware to decrease errors due to CP movement does not appear justified.…”

“…Other CP technologies can be categorized as emerging and represent promising opportunities to advance targeted, precision irrigation, such as site-specific VRI and associated sensor technologies, which are the subject of four Special Collection articles (Colaizzi et al, 2019;O'Shaughnessy et al, 2019a, b;Stone et al, 2019). These articles present important information for characterizing and monitoring VRI and discuss how VRI technologies must also consider additional factors, such as weather, plant water stress information, and cultivar characteristics.…”