With the Google Earth Engine, it’s very easy to calculate the amplitude of any time-series datasets. The amplitude in wave physics is defined as the distance between the high and the low peak as shown in the picture below. Similarly, for any raster datasets for a time series, the amplitude is the difference of the highest and the lowest value for a pixel across the time-series.

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Here we will calculate the amplitude of Tree Canopy Cover (TCC) and Tree Canopy Height (TCH) for a time-series utilizing the datasets from UMD from 1988 to 2018. The amplitude of TCC and TCH are defined as the difference of value between the maximum and minimum TCC and TCH respectively.  The only caveat is that all the image in the image collection needs to have the same band name.

var tcc = ee.ImageCollection("projects/servir-mekong/yearly_primitives_smoothed/tree_canopy"),
    tch = ee.ImageCollection("projects/servir-mekong/yearly_primitives_smoothed/tree_height"),
    mekong = ee.FeatureCollection("users/biplov/gadm-mekong");

// TCC Amplitude
var maxTCC = tcc.max();
var minTCC = tcc.min();
var ampTCC = maxTCC.subtract(minTCC);
ampTCC = ampTCC.updateMask(ampTCC.gt(0));
ampTCC = ampTCC.clip(mekong);
Map.addLayer(ampTCC, {min:1, max:25, palette: 'd7191c,fdae61,ffffbf,abdda4,2b83ba'}, 'ampTCC');

// TCH Amplitude
var maxTCH = tch.max();
var minTCH = tch.min();
var ampTCH = maxTCH.subtract(minTCH);
ampTCH = ampTCH.updateMask(ampTCH.gt(0));
ampTCH = ampTCH.clip(mekong);
Map.addLayer(ampTCH, {min:1, max:25, palette: 'd7191c,fdae61,ffffbf,abdda4,2b83ba'}, 'ampTCH');

Find the full code here.

Happy Earth Science 🙂