How does one extract NDVI data from a band?

Question

I am trying to look at the change in NDVI over time for a polygon, and I want to have access to the NDVI values themselves, rather than chart or map them. So far, all I seem to be able to do is select a single pixel, chart the NDVI and then export the data as a CSV. This method would be extremely impractical if I wanted to do this for a polygon instead of a pixel.

var chart = ui.Chart.image.series({
  imageCollection: withNDVI.select('ndvi'),
  region: Point,
  reducer: ee.Reducer.max(),
  scale: 30
}).setOptions({title: 'NDVI over time'});

print(chart);

I'm using the above code to plot NDVI over time.

score 1 · Answer 1 · answered Apr 02 '18 at 16:05

"Have access to" is not really specific enough. You can check the getRegion() method on an image collection. You may also want to check the toCollection() reducer in order to turn the pixels into a FeatureCollection. For more complicated exports of time series in regions, this reference may help.

How does one extract NDVI data from a band?

1 Answers1