I have a code in GEE which creates two images from sentinel-1 (SAR) and from sentinel-2 (NDVI) , creates from them paired image and then creates scatter plot from the two bands in the image. In order to create the scatterplot, I know I need to run kind of training and i'm a bit confused about it and about my results.
This is the code I have that seemed to be working:
// make an image for the two variables var pairedImage = ee.ImageCollection.fromImages([imageNDVIcor,SARreproject]).toBands().rename(["NDVI","SAR"]); print("pairedImage",pairedImage); // Generate a sample of points within the region var sample = pairedImage.sampleRegions(geometry, null, 150); print("sample",sample); // Generate chart from sample var chart = ui.Chart.feature.byFeature(sample, 'NDVI', 'SAR') .setChartType('ScatterChart'); print("chart",chart);
The point is that I get results that look nice but I can't understand, for example: this is suppose to be my point? what is this? what are those values?
var sample = pairedImage.sampleRegions(geometry, null, 500);
and this is with: var sample = pairedImage.sampleRegions(geometry, null, 150);:
How come using less points lead to more ponts in the correlation? I feel confused and i'm afraid that I don't understand something very basic with the sample points.
My end goal is to understand why I have gotten those two different charts when 500 has lesspoints than 100 and 1000 had the least. what'shapenning here?