The impacts of heating strategy on soil moisture estimation using actively heated fiber optics

The impacts of heating strategy on soil moisture estimation using actively heated fiber optics

Dong, J. (TU Delft Water Resources; USDA-ARS Hydrology and Remote Sensing Laboratory)
Agliata, Rosa (Università della Campania)
Steele-Dunne, S.C. (TU Delft Water Resources)
Hoes, O.A.C. (TU Delft Water Resources)
Bogaard, T.A. (TU Delft Water Resources)
Greco, Roberto (Università della Campania)
van de Giesen, N.C. (TU Delft Water Resources)

2017-09-13

Several recent studies have highlighted the potential of Actively Heated Fiber Optics (AHFO) for high resolution soil moisture mapping. In AHFO, the soil moisture can be calculated from the cumulative temperature (T_cum), the maximum temperature (T_max), or the soil thermal conductivity determined from the cooling phase after heating (λ). This study investigates the performance of the T_cum, T_max and λ methods for different heating strategies, i.e., differences in the duration and input power of the applied heat pulse. The aim is to compare the three approaches and to determine which is best suited to field applications where the power supply is limited. Results show that increasing the input power of the heat pulses makes it easier to differentiate between dry and wet soil conditions, which leads to an improved accuracy. Results suggest that if the power supply is limited, the heating strength is insufficient for the λ method to yield accurate estimates. Generally, the T_cum and T_max methods have similar accuracy. If the input power is limited, increasing the heat pulse duration can improve the accuracy of the AHFO method for both of these techniques. In particular, extending the heating duration can significantly increase the sensitivity of T_cum to soil moisture. Hence, the T_cum method is recommended when the input power is limited. Finally, results also show that up to 50% of the cable temperature change during the heat pulse can be attributed to soil background temperature, i.e., soil temperature changed by the net solar radiation. A method is proposed to correct this background temperature change. Without correction, soil moisture information can be completely masked by the background temperature error.

Active DTS
Heating strategy
Soil moisture
Soil temperature
OA-Fund TU Delft

http://resolver.tudelft.nl/uuid:6d5c18a5-99c4-457c-86e6-1b440baa509d

https://doi.org/10.3390/s17092102

1424-8220

Sensors, 17 (9), 1-11

Institutional Repository

journal article

© 2017 J. Dong, Rosa Agliata, S.C. Steele-Dunne, O.A.C. Hoes, T.A. Bogaard, Roberto Greco, N.C. van de Giesen