/*
This Google Earth Engine script downloads satellite-derived topographical and enviromental variables.
Date: 10/18/2017
Author: Dr. Alemayehu Midekisa 
Email: alemayehu.midekisa@ucsf.edu
*/

// Get a feature collection with just the E8 countries.
var countries = ee.FeatureCollection('ft:1tdSwUL7MVpOauSgRzqVTOwdfy17KDbw-1d9omPw');
var Burkina = countries.filter(ee.Filter.eq('Country', 'Burkina Faso'));
Map.centerObject(Burkina, 9);

// Create a blank image to accept the polygon outlines.
var image1 = ee.Image(0).mask(0);
// Outline using the specified color and width.
var image2 = image1.paint(Burkina, 'ff00ff', 2); 
Map.addLayer(image2, {'palette': '000000', 'opacity': 0.5}, "Burkina Faso");

var evicollection = ee.ImageCollection('MODIS/MYD13Q1').filterDate('2017-01-01', '2017-03-31').select("EVI");

// Palette
var EVI_PALETTE = 'FFFFFF, CE7E45, DF923D, F1B555, FCD163, 99B718, 74A901, 66A000, 529400,' +
    '3E8601, 207401, 056201, 004C00, 023B01, 012E01, 011D01, 011301';
var Elevation_PALETTE = "000000, CC9900, 99CC00, 009900, 006600";

//**********************
// Elevation
//**********************
var elev = ee.Image('CGIAR/SRTM90_V4').clip(Burkina);
var Elevation_PALETTE = "000000, FFFF00";
Map.addLayer(elev, {min:0, max:2000, bands:["elevation"], "palette": Elevation_PALETTE}, "Elevation Burkina");

var elev_Burkina_path = elev.getDownloadURL({
  'name': 'Elevation',
  'scale': 250,
  'crs': 'EPSG:32649',
  'region': '[[110.1955, 35.8738], [112.0275, 35.8738],[112.0275, 34.5129], [110.1955, 34.5129]]',
});
print("Download Elevation", elev_Burkina_path);


//***********************************
// Enhanced Vegetation Index (EVI)
//***********************************
var VI_Res = function(image) {
    var VI_temp = image.toFloat().multiply(0.0001);
    image = image.addBands(VI_temp);
    return image;
}
var EVI_new = evicollection.map(VI_Res);
var EVI_2017 = ee.ImageCollection(EVI_new).filterDate('2017-01-01', '2017-03-31').select("EVI_1");
var EVI_2017_Burkina = EVI_2017.median().clip(Burkina);

Map.addLayer(EVI_2017_Burkina, {min:-1, max:1, bands:["EVI_1"], "palette": EVI_PALETTE}, "EVI  Burkina");
var EVI_2014_Burkina_path = EVI_2014_Zambia.getDownloadURL({
  'name': 'EVI_2017_Zambia',
  'scale': 250,
  'crs': 'EPSG:32649',
  'region': '[[110.1955, 35.8738], [112.0275, 35.8738],[112.0275, 34.5129], [110.1955, 34.5129]]',
});
print("Download EVI", EVI_2017_Burkina_path);