WIRIS AGRO – camera for water stress quantification

slide n.: 1© Workswell www.workswell.eu
WIRIS AGRO – CAMERA FOR WATER STRESS
QUANTIFICATION
JAN SOVA

CWSI – CROP WATER STRESS INDEX
THEORETICAL BACKGROUND

▪ The crop water stress index (CWSI) was developed as a normalized index
to quantify stress and overcome the effects of other environmental
parameters affecting the relationship between stress, plant temperature
and air temperature. CWSI has been widely used for crop water status
monitoring [1].

▪ The idea of CWSI is since in the case of absence of water intake from the
soil the plant is not able to cool down own body by transpiration.
Evapotranspiration is the water loss occurring from the processes of
evaporation and transpiration.
Evaporation occurs when water changes to
vapor on either soil or plant surfaces.
Transpiration refers to the water lost through
the leaves of plants. The cooling of the plant
body is thus affected by the evaporation of
water from its surface. This water passes
through the body of the plant and is released
to the surface and then evaporated.

CWSI PICTURE TAKEN BY WIRIS AGRO

CWSI MAP – WIRIS AGRO & AGISOFT

CWSI – STRESS LEVELS

WATER STRESS BY COUNTRY
The World Resources Institute, the nonprofit research organization that conducted the study, classifies “highly” water-stressed
countries as those that withdraw between 40% and 80% of their available water each year, while “extremely highly” stressed nations
draw down more than 80%. There are 37 countries in the “extreme” category.

WORKSWELL WIRIS AGRO
CAMERA DESCRIPTION

WORKSWELL WIRIS AGRO
□ Workswell’s WIRIS Agro is the first device of its kind designed to map
water stress across large areas in the field of precision agriculture. The
aim of this method and device is to determine the value of water stress
in the plant stand.
Workswell WIRIS Agro & Gremsy S1

INTERFACES

TECHNICAL TABLE

COLOUR MAPS
□ WIRIS Agro offers four different colourmaps. From the point of view of
data and their processing it is not important which one of the colourmap
you choose. In the application point of view a suitable palette choice can
be very helpful.
□ Each colourmap in the WIRIS
Agro camera is always defined
in this way: the palette is black
and white away from the value
0 (negative values below the
range) and away from the
value 100% (values above the
range).

COLOUR MAPS
□ Colourmap „ CROP“ – General colourmap used mainly to detect the
presence of drought without using an irrigation system. The most
commonly used palette in connection with the use of the WIRIS Agro
camera.
□ Colourmap „CROPSTEP“ - same colourmap as ”CROP” , there are steps
changes in color. That colourmap is suitable for quick and orientation
evaluation during flight.
□ Colourmap „WATER“ - Colourmap suitable especially for evaluation of
irrigation systems. The blue color corresponds to places where the level
of water stress is very low, and more water could be saved. If the water
stress values across the field are too inhomogeneous (large scattering of
values), the irrigation system should be more homogeneous.
□ Colourmap „ WATERSTEP “ - same colourmap as ”WATER” , there are
steps changes in color. That colourmap is suitable for quick and
orientation evaluation during flight.

BIOMASS COVER INDEX
□ BCI (Biomass Cover index) is related to the evaluation of the mass of
vegetation in the RGB scene. Based on data from the RGB camera,
surfaces containing green vegetation are evaluated and the percentage
of these areas is compared to other (non-vegetation) areas that are
masked by white color in the RGB image. BCI is adjustable by simple
thresholding by user.

NDVI AND CWSI COMPARISON

CWSI X NDVI
X
Workswell WIRIS Agro & Gremsy S1 Phantom 4 Multispectral

CWSI X NDVI
□ CWSI and NDVI are two completely different indexes. So,
their direct comparison is therefore not possible. Yet we
have to make a basic comparison, as NDVI (and similar
vegetation indices) is currently the most used remote sensing
instrument in the area of precision agriculture.
□ We cannot say that one index (CWSI x NDVI) is better than
the other. Each serves a different purpose! However, we
believe that CWSI could provide a significantly wider
application area.

CWSI X NDVI
□ Situation in a real time (CWSI) x dead or live (NDVI)
□ Before it is too late (CWSI) x it is to late (NDVI)
□ physiological process (CWSI) x long-term impact
(NDVI)

QUESTIONS?
HTTPS://WWW.DRONE-THERMAL-CAMERA.COM/

REFERENCES
□ [1] Carlos Poblete-Echeverría et. al, Analysis of crop water stress index (CWSI) for estimating
stem water potential in grapevines: Comparison between natural reference and baseline
approaches, January 2017 Acta horticulturae
□ [2] Reginato, R.J., J. Howe, Irrigation scheduling using crop indicators, Journal of Irrigation
and Drainage Engineering 111(2): 125-133
□ [3] N. Agam et. al, An insight to the performance of crop water stress index for olive trees,
Agricultural Water Management 118 (2013) 79–86
□ [4] Tanriverdi, C. , Atilgan, A. , Degirmenci, H. , Akyuz, A., Comparasion of Crop Water Stress
Index (CWSI) and Water Deficit Index (WDI) by using Remote Sensing (RS), Infrastruktura i
Ekologia Terenów Wiejskich, 2017 | nr III/1 | 879—894
□ [5] Ehrler, W.L., Idso, S.B., Jackson, R.D., Reginato, R.J. Wheat canopy temperature: relation
to plant water potential. Agron. J. 70, 251±256, 1978
□ [6] Idso, S. B. et al., Non-water-stressed baseline: a key to measuring and interpreting plant
water stress. Agriculture Meteorolgy; 27: 59-70

ACKNOWLEDGMENT

WIRIS AGRO – camera for water stress quantification

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