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I am supposed to collect NDVI values for some states in the USA. I understand NDVI is supposed to be between -1 and 1, but my values are in the 1000s. Can someone please help me with the interpretation of the values I get or how to get it right? Here is the code I used:

var startDate = '2000-01-01';
var endDate = '2019-05-01';

var collection = ee.ImageCollection('MODIS/006/MOD13Q1').filterDate(startDate,endDate).select('NDVI');

var reducers = ee.Reducer.min().combine({
              reducer2: ee.Reducer.max(), sharedInputs: true}).combine({
              reducer2: ee.Reducer.stdDev(), sharedInputs: true}).combine({
              reducer2: ee.Reducer.mode(), sharedInputs: true}).combine({
              reducer2: ee.Reducer.median(), sharedInputs: true}).combine({
              reducer2: ee.Reducer.mean(), sharedInputs: true});

print(ui.Chart.image.series(collection, KansasMap, reducers, 200));
4

If you check the MODIS Vegetation Index User’s Guide (page 9) or the MODIS MOD13Q1 product page you will see MODIS uses a scaling factor of 0.0001 and has a valid range from -2000 to 10000.

enter image description here

In order to get values between -1 and 1, you have to multiply the values by the scaling factor.

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