The water body extraction algorithm based on satellite remote sensing is mainly aimed at large and medium-sized lakes or large rivers. When applied to small water bodies

it is easy to misjudge. Sentinel 2 satellite multi-spectral remote sensing data spatial resolution of 10

20

60 meters

a double star time resolution of 5 days

and high temporal and spatial resolution. Therefore

this paper uses the sentinel-2 green light band (560nm)

red edge band (705nm)

near infrared band (842nm

865nm) and short wave infrared band (2190) for remote sensing reflectance. A new water index algorithm (Red Edge based Water Index

RWI for short) is proposed for the extraction of finely water. The normalized remote sensing reflectivity of vegetation

shadow

building

mixed pixel

bare soil and water body is compared and analyzed. The mechanism explains why RWI has better effect of extracting fine water body than other water body indexes.