MODIS_overlay

// 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
}






var img = ee.Image(ic.first())
Map.addLayer(img.select(['swir2','swir1','nir']),{min:0,max:0.4},'infrared')

var hot = HOTMAP(img)
Map.addLayer(hot,{color:'red'},'hot_vectors')

Map.centerObject(Monterey_geom,10)




// Landsat geom, date and projection
var LandsatImg = img.select(['blue']);
var LandsatGeom = LandsatImg.geometry();
var LandsatDate = ee.Date(LandsatImg.get('system:time_start'));
var crs = LandsatImg.projection().crs()
//var scale = LandsatImg.projection().nominalScale()

// MODIS fire collection
var FIRMS = ee.ImageCollection('FIRMS');
//var crs = ee.Image(FIRMS.first()).projection().crs()
var scale = ee.Image(FIRMS.first()).projection().nominalScale()

// MODIS fire alerts within 24 hours of Landsat image acquisition
var startDate = LandsatDate.advance(-12,'hour');
var stopDate  = LandsatDate.advance(+12,'hour');
var MODISalerts = FIRMS.select(['T21']).filterDate(startDate,stopDate)

// Reduce MODIS alerts to single binary image
var MODIScount = ee.Image(MODISalerts.count())
var MODISbinary = MODIScount.eq(MODIScount).rename('MODIS_binary_alert')

// Reproject alerts
var MODISreproject = MODISbinary.reproject({crs:crs,scale:scale})

// MODIS fire vectors
var MODISvectors = MODISreproject.reduceToVectors({
  geometry: LandsatGeom,
  eightConnected:true,
  labelProperty:'modis_fire',
  maxPixels:2e8,
  crs:crs,
  scale:scale
});

// MODIS display
var vectorDisplay = ee.Image(0).updateMask(0)
  .clip(LandsatGeom)
  .paint(MODISvectors, '000000', 3);
  
//Map.addLayer(MODISreproject, {palette: 'gray'})
Map.addLayer(vectorDisplay, {palette: '00FF00'}, 'MODIS fire alerts');
Map.setCenter(-121.7093, 36.3538,10)