Visualizing the 'Cartographic Lag' in GEE: A comparative analysis showing how real-time physical infrastructure (Sentinel-1 SAR 2026) outpaces annual foundation models (DeepMind AlphaEarth 2025) in rapidly growing megacities.

cartographic_lag_sample.js

// 1. Define exact coordinates (New Administrative Capital, Egypt)
var lon = 31.75; 
var lat = 30.01; 
var targetPoint = ee.Geometry.Point([lon, lat]);
var nrc = targetPoint.buffer(500).bounds();

Map.setCenter(lon, lat, 12);

// Load Night Lights (VIIRS)
// Comparing 2021 with the last 6 months available (up to early 2026)
var lightsOld = ee.ImageCollection("NOAA/VIIRS/DNB/MONTHLY_V1/VCMSLCFG")
  .filterDate('2021-01-01', '2021-12-31')
  .median()
  .select('avg_rad');

var lightsNew = ee.ImageCollection("NOAA/VIIRS/DNB/MONTHLY_V1/VCMSLCFG")
  .filterDate('2025-09-01', '2026-02-28')
  .median()
  .select('avg_rad');

var lightDiff = lightsNew.subtract(lightsOld);

// Load Radar (Sentinel-1)
var radar2026 = ee.ImageCollection('COPERNICUS/S1_GRD')
  .filterBounds(nrc)
  .filterDate('2026-01-01', '2026-03-04')
  .filter(ee.Filter.listContains('transmitterReceiverPolarisation', 'VV'))
  .median();

// Real Satellite Image (Sentinel-2)
var optical2026 = ee.ImageCollection("COPERNICUS/S2_SR_HARMONIZED")
  .filterBounds(nrc)
  .filterDate('2026-01-01', '2026-03-04') // Data up to today
  .sort('CLOUDY_PIXEL_PERCENTAGE')
  .first();

// Sample: super simple filter to isolate buildings
var buildingsOnly = radar2026.select('VV').gt(-12); 
var visibleBuildings = buildingsOnly.updateMask(buildingsOnly);

// AlphaEarth Foundations (Google DeepMind)
var alphaEarth = ee.ImageCollection("GOOGLE/SATELLITE_EMBEDDING/V1/ANNUAL")
  .filterBounds(nrc) // Using your exact area in Egypt
  .filterDate('2024-01-01', '2025-12-31') // Getting the latest available year
  .first();

Map.addLayer(radar2026.select('VV'), {min: -20, max: 0}, '1. Radar 2026 (Current)');
Map.addLayer(lightDiff, {min: 0, max: 15, palette: ['black', 'blue', 'cyan', 'yellow', 'red']}, '2. Night Lights Growth (21 vs 26)');
Map.addLayer(optical2026, {bands: ['B4', 'B3', 'B2'], min: 0, max: 3000}, '3. Satellite Photo 2026');
Map.addLayer(visibleBuildings, {palette: ['#ff0000']}, '4. Radar: Buildings Only (Highlighted)');
Map.addLayer(alphaEarth, {
  bands: ['A01', 'A16', 'A09'], 
  min: -0.5, 
  max: 0.5
}, '5. AI Vision: AlphaEarth (Urban Composite: A01, A16, A09)');

// Add a red marker to the exact coordinates
Map.addLayer(targetPoint, {color: 'red'}, 'Target Location Marker');