get_layer_func

// released under Open Source GPL License Copyright © 2023 Ka Hei Chow

// ######################################### //
// ######    Functions for Map        ###### //
// ######     Comparison Tool         ###### //
// ######################################### //

/**
 * This script contains functions to get different geospatial layers
 * to be fired once data layer is selected by users
 */

// get Global Extreme Heat Hazard
// https://gee-community-catalog.org/projects/heat-hazard/

// 100 year return period
exports.get_heat_100y = function get_heat_100y(aoi) {
  var global_extreme_heat_hazard = ee.ImageCollection("projects/sat-io/open-datasets/WORLD-BANK/global-ext-heat-hazard");
  var heat_100y = global_extreme_heat_hazard.filter(ee.Filter.eq('id_no', "intensity_returnperiod100y")).first();
  return heat_100y.clip(aoi);
};

// 20 year return period
exports.get_heat_20y = function get_heat_20y(aoi) {
  var global_extreme_heat_hazard = ee.ImageCollection("projects/sat-io/open-datasets/WORLD-BANK/global-ext-heat-hazard");
  var heat_20y = global_extreme_heat_hazard.filter(ee.Filter.eq('id_no', "intensity_returnperiod20y")).first();
  return heat_20y.clip(aoi);
};

// 5 year return period
exports.get_heat_5y = function get_heat_5y(aoi) {
  var global_extreme_heat_hazard = ee.ImageCollection("projects/sat-io/open-datasets/WORLD-BANK/global-ext-heat-hazard");
  var heat_5y = global_extreme_heat_hazard.filter(ee.Filter.eq('id_no', "intensity_returnperiod5y")).first();
  return heat_5y.clip(aoi);
};

// get Landscan latest population layer (2021)
// https://gee-community-catalog.org/projects/landscan/?h=landscan
exports.get_landscan_pop = function get_landscan_pop(aoi) {
  var landscan_global = ee.ImageCollection("projects/sat-io/open-datasets/ORNL/LANDSCAN_GLOBAL");
  var landscan_2021 = landscan_global.sort('system:time_start',false).first();
  return landscan_2021.clip(aoi);
};

// get Palmer Drought Severity Index (historical average between 2010 and 2023)
// https://developers.google.com/earth-engine/datasets/catalog/IDAHO_EPSCOR_TERRACLIMATE
exports.get_pdsi = function get_pdsi(aoi) {
  // return the list of coordinates
  var centroid = aoi.first().geometry().centroid();
  var listCoords = ee.Array.cat(centroid.coordinates(), 0); 
  
  var yCoords = ee.List(listCoords).getInfo()[1];
  var south = ee.Number(yCoords).lt(0);
  
  var shift = south.multiply(6).getInfo();
  
  var summerFilter = ee.Filter.calendarRange(5+shift, 9+shift, "month");
  
  var yearFilter = ee.Filter.date(ee.Date("2010-01-01"),ee.Date("2023-01-01"));
  
  var dataset = ee.ImageCollection('IDAHO_EPSCOR/TERRACLIMATE')
                    .filter(yearFilter).filter(summerFilter);
  
  var drought_index = dataset.select('pdsi').median().multiply(0.01).clip(aoi);

  return drought_index;
};

// get MODIS temperature difference between daytime and nighttime
// https://developers.google.com/earth-engine/datasets/catalog/OpenLandMap_CLM_CLM_LST_MOD11A2-DAYNIGHT_M_v01
exports.get_temp_diff = function get_temp_diff(aoi) {
  var temp_diff = ee.Image("OpenLandMap/CLM/CLM_LST_MOD11A2-DAYNIGHT_M/v01")
  .reduce('mean')
  .multiply(0.02);
  return temp_diff.clip(aoi);
};

// get GHSL urbanization degree
// https://developers.google.com/earth-engine/datasets/catalog/JRC_GHSL_P2016_SMOD_POP_GLOBE_V1
exports.get_urban_degree = function get_urban_degree(aoi) {
  var dataset = ee.ImageCollection('JRC/GHSL/P2016/SMOD_POP_GLOBE_V1')
                  .filter(ee.Filter.date('2015-01-01', '2015-12-31'));
  var degreeOfUrbanization = dataset.select('smod_code').sum().clip(aoi);
  return degreeOfUrbanization;
};

// get urban heat island index daytime
// https://developers.google.com/earth-engine/datasets/catalog/YALE_YCEO_UHI_Summer_UHI_yearly_pixel_v4
exports.get_uhi_day = function get_uhi_day(aoi) {
  var uhi = ee.ImageCollection('YALE/YCEO/UHI/Summer_UHI_yearly_pixel/v4')
  .select('Daytime')
  .filter(ee.Filter.inList('system:index', ["2018"]))
  .first();
  return uhi.clip(aoi);
};

// get urban heat island index nighttime
// https://developers.google.com/earth-engine/datasets/catalog/YALE_YCEO_UHI_Summer_UHI_yearly_pixel_v4
exports.get_uhi_night = function get_uhi_night(aoi) {
  var uhi = ee.ImageCollection('YALE/YCEO/UHI/Summer_UHI_yearly_pixel/v4')
  .select('Nighttime')
  .filter(ee.Filter.inList('system:index', ["2018"]))
  .first();
  return uhi.clip(aoi);
};

// get density of forest class within 5 km radius in Land Cover
// https://developers.google.com/earth-engine/datasets/catalog/ESA_WorldCover_v200
exports.get_forest_density = function get_forest_density(aoi) {
  
  var bbox = aoi.geometry();
  
  // get urban areas
  var lulc = ee.ImageCollection('ESA/WorldCover/v200')
  .first()
  .clip(bbox);
  
  var urban_mask = lulc.eq(10);
  
  // calculate urban density
  var reduceNeighborhood = urban_mask.reduceNeighborhood(
    ee.Reducer.mean(), 
    ee.Kernel.circle(5000, 'meters')
  ).multiply(100).toByte();
  
  return reduceNeighborhood;
};

// get density of cropland class within 5 km radius in Land Cover
// https://developers.google.com/earth-engine/datasets/catalog/ESA_WorldCover_v200
exports.get_cropland_density = function get_cropland_density(aoi) {
  
  var bbox = aoi.geometry();
  
  // get urban areas
  var lulc = ee.ImageCollection('ESA/WorldCover/v200')
  .first()
  .clip(bbox);
  
  var urban_mask = lulc.eq(40);
  
  // calculate urban density
  var reduceNeighborhood = urban_mask.reduceNeighborhood(
    ee.Reducer.mean(), 
    ee.Kernel.circle(5000, 'meters')
  ).multiply(100).toByte();
  
  return reduceNeighborhood;
};


// get density of urban class within 5 km radius in Land Cover
// https://developers.google.com/earth-engine/datasets/catalog/ESA_WorldCover_v200
exports.get_urban_density = function get_urban_density(aoi) {
  
  var bbox = aoi.geometry();
  
  // get urban areas
  var lulc = ee.ImageCollection('ESA/WorldCover/v200')
  .first()
  .clip(bbox);
  
  var urban_mask = lulc.eq(50);
  
  // calculate urban density
  var reduceNeighborhood = urban_mask.reduceNeighborhood(
    ee.Reducer.mean(), 
    ee.Kernel.circle(5000, 'meters')
  ).multiply(100).toByte();
  
  return reduceNeighborhood;
};


// get critical infrastructure spatial index
// https://www.nature.com/articles/s41597-022-01218-4
exports.get_cisi = function get_cisi(aoi) {
  return ee.Image("projects/sat-io/open-datasets/CISI/global_CISI").clip(aoi);
};

// get relative wealth index
// https://dataforgood.facebook.com/dfg/tools/relative-wealth-index
exports.get_rwi = function get_rwi(aoi) {
  // get RWI data layer from community project (Layer 2)
  var rwi_ds = ee.FeatureCollection("projects/sat-io/open-datasets/facebook/relative_wealth_index");
  
  // buffer point grid to fill gaps
  var aoi_rwi = rwi_ds.filterBounds(aoi).map(
    function(point) {
    return point.buffer(2000);
  });
  
  // convert point grid to raster image
  var rwi = aoi_rwi.filter(ee.Filter.notNull(['rwi']))
    .reduceToImage({
      properties: ['rwi'],
      reducer: ee.Reducer.mean(),
  }); 
  return rwi;
};