google-earth-enginejavascriptnormalized-difference-water-index
I'm a new learner of Google Earth Engine.
What I am doing right now is to extract water bodies from Landsat 8 using such water index as NDWI(normalized difference water index) in GEE.
Is there any available function in the binarization of the water bodies to obtain the optimal threshold (such as the OTSU)?
I found it difficult to perform the binarization after calculating the NDWI.
You are the right way. Follow this process
(b1 - b2)/(b1 + b2) where b1 is green band and b2 is SWIR1. Read this paper for more information about MNDWI.(b1 le 0)*0 + (b1 gt 0)*1 using MNDWI result. Where le is lower/equal than b1 and gt greater than b1.Vector / Raster to vector and convert it. This will result in a .evf file, to save as shapefile use Vector / Classic EVF to Shapefile.
After some research and help, I finally have the solution to the described problem, which I also want to share with the community.
https://code.earthengine.google.com/8b39abcdf63cd569ee09a6ac2eb68c93?hideCode=true
Concerning the truncated satellite pictures this hint helped me. https://groups.google.com/forum/#!msg/google-earth-engine-developers/g2ZByrxm8NE/exd7WWesBQAJ
With the following line of code I could filter the undesired images:
.filter(ee.Filter.contains({leftField: ".geo", rightValue: aoi})) // Filter partial S1-Images of AOI
Best Answer
Otsu's method for finding an optimal threshold has been implemented in Earth Engine. See the blog post: Otsu’s Method for Image Segmentation