burn scars

// Monterey_Fire
var Monterey_geom = ee.Geometry.Point(-121.7326, 36.3395)
var Monterey_date = ee.Date('2016-07-31')

// Landsat 8 collection
var ic = ee.ImageCollection('LANDSAT/LC8_L1T_TOA')
  .filterBounds(Monterey_geom)
  .filterDate(Monterey_date,'3000-01-01')
  .select(['B2','B3','B4','B5','B6','B7'],['blue','green','red','nir','swir1','swir2']);

// HOTMAP detection
function HOTMAP(img) {

  // wavebands
  var n  = img.select('nir')
  var s1 = img.select('swir1')
  var s2 = img.select('swir2')

  // alpha detection
  var a1 = s2.divide(s1).gt(1.4)
  var a2 = s2.divide(n).gt(1.4)
  var a3 = s2.gt(0.15)
  var alpha = a1.and(a2).and(a3).rename('alpha')

  // beta detection
  var b1 = s1.divide(n).gt(2)
  var b2 = s1.gt(0.5)
  var beta = b1.and(b2).rename('beta')

  // potential hot pixels
  var potentialHot = alpha.or(beta)
  var hotPixels = potentialHot.updateMask(potentialHot)
  
  // hot pixel clusters (count alpha pixels)
  var hotClusters = hotPixels.addBands(alpha).reduceToVectors({
    eightConnected:true,
    maxPixels:2e8,//might seem like a lot but MOST pixels are masked
    reducer:ee.Reducer.count()
  })
  
  // hot pixel clusters must contain alpha pixels
  var validHotClusters = hotClusters.filter(ee.Filter.gt('count', 0));
  
  // Image properties
  var fileID = img.get('system:index')
  var satID = ee.String(fileID).slice(0,3)
  var timestamp = img.get('system:time_start')
  
  // Assign properties
  var clusters = validHotClusters.map(function(feature) {
    var clusterGeom = feature.geometry()
    var clusterArea = feature.geometry().area(1) // i.e. to within 1 m2
    var cluster = ee.Feature(clusterGeom,{
      fileID:fileID,
      satID:satID,
      timestamp:timestamp,
      area:clusterArea
    })
    return cluster
  })
  
  return clusters
}


// Display Fires
var img = ee.Image(ic.first())
var rgb = img.select(['red','green','blue'])
var ir = img.select(['swir2','swir1','nir'])
var hot = HOTMAP(img)
Map.addLayer(ir,{min:0,max:0.4},'infrared')
Map.addLayer(rgb,{min:0,max:0.4},'visible')
Map.addLayer(hot,{color:'red'},'hot_vectors')
Map.centerObject(Monterey_geom,10)



// Burn Scars
//
//var NBR = img.normalizedDifference(['nir','swir2'])
// Map.addLayer(hsv,{},'hsv')
// Map.addLayer(NBR,{},'NBR')
// _________________________________________________

function find_burn_scars(img) {
  
  var hsv = ir.rgbToHsv()
  var notGrey = hsv.select(['saturation']).gt(0.2)
  var hue = hsv.select(['hue']).lt(0.2)
  var dull = hsv.select('value').lt(0.35)
  var lowNir = img.select(['nir']).lt(0.25)
  
  var burnt = notGrey.and(hue).and(dull).and(lowNir)
  var burnt_masked = burnt.updateMask(burnt)
  
  return burnt_masked
  
}

var burnt = find_burn_scars(img)


var R = burnt.divide(1000)
var G = burnt
var B = burnt.divide(1000)

var burntRGB = R.addBands(G).addBands(B)


Map.addLayer(burntRGB,{min:0,max:1},'burnt')