Smartphone-based estimation of green cover depends on the camera used

Smartphone-based visual assessment of vegetation cover is a promising, fast, and repeatable approach that allows land managers to compare measurements on their farm with other farms. This study determined the influence of the smartphone device on green cover measurements on several crops. The hypothesis was that different smartphones would provide similar green cover (reflectance) for management purposes (i.e., <10% difference). Forty fields in Finland were sampled between 10 and 28 July 2020 with Motorola Moto G7 and Samsung Galaxy A6 smartphones. The results were compared also with Sentinel-2 remote sensing of normalized difference vegetation index (NDVI) and biomass quadrants. The two smartphones had different green reflectance values that were correlated to each other. Both green reflectance measurements correlated with the NDVI that was measured with the Sentinel 2 satellite sensor and biomass. These findings suggest that smartphone-based monitoring can be used at least to classify vegetation to low, medium, and high density but that results from different cameras should not be compared.

Automated summary

The study suggests that smartphone-based visual assessment of vegetation cover is a promising method for comparing measurements on different farms. Different smartphones may have varying green reflectance values, but they are correlated with the NDVI and biomass measured by the Sentinel 2 satellite.