Eyes in the Sky, Boots on the Ground : Assessing Satellite- and Ground-Based Approaches to Crop Yield Measurement and Analysis in Uganda
Crop yields in smallholder systems are traditionally assessed using farmer-reported information in surveys, occasionally by crop cuts for a sub-section of a farmer's plot, and rarely using full-plot harvests. Accuracy and cost vary dramaticall...
| Main Authors: | , , , , , , |
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| Format: | Working Paper |
| Language: | English |
| Published: |
World Bank, Washington, DC
2018
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| Subjects: | |
| Online Access: | http://documents.worldbank.org/curated/en/556261522069698373/Eyes-in-the-sky-boots-on-the-ground-assessing-satellite-and-ground-based-approaches-to-crop-yield-measurement-and-analysis-in-Uganda http://hdl.handle.net/10986/29554 |
| Summary: | Crop yields in smallholder systems are
traditionally assessed using farmer-reported information in
surveys, occasionally by crop cuts for a sub-section of a
farmer's plot, and rarely using full-plot harvests.
Accuracy and cost vary dramatically across methods. In
parallel, satellite data is improving in terms of spatial,
temporal, and spectral resolution needed to discern
performance on smallholder plots. This study uses data from
a survey experiment in Uganda, and evaluates the accuracy of
Sentinel-2 imagery-based, remotely-sensed plot-level maize
yields with respect to ground-based measures relying on
farmer self-reporting, sub-plot crop cutting (CC), and
full-plot crop cutting (FP). Remotely-sensed yields include
two versions calibrated to FP and CC yields (calibrated),
and an alternative based on crop model simulations, using no
ground data (uncalibrated). On the ground, self-reported
yields explained less than 1 percent of FP (and CC) yield
variability, and while the average difference between CC and
FP yields was not significant, CC yields captured
one-quarter of FP yield variability. With satellite data,
both calibrated and uncalibrated yields captured FP yield
variability on pure stand plots similarly well, and both
captured half of FP yield variability on pure stand plots
above 0.10 hectare. The uncalibrated yields were
consistently 1 ton per hectare higher than FP or CC yields,
and the satellite-based yields were less well correlated
with the ground-based measures on intercropped plots
compared with pure stand ones. Importantly, regressions
using CC, FP and remotely-sensed yields as dependent
variables all produced very similar coefficients for yield
response to production factors. |
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