STARTERS

MODIS

Earth Engine provides a somewhat staggering number of different MODIS products as cloud assets. The sheer number of products available can make it a little confusing to navigate. This page aims to help by introducing some key concepts for working with MODIS.

key terms

sensor and satellites

The Moderate Resolution Imaging Spectrometer, or MODIS, is a sensor onboard two satellites:

• Terra: originally called as EOS AM-1
• Aqua: originally called EOS PM-1

orbits

These two satellites image Earth’s entire surface once every 1-2 days. The video below shows the orbit of the Aqua satellite.

bands

Compared to Landsat and Sentinel, MODIS bucks convention for band names. It also differs from other sensors by having a second NIR band (between NIR and SWIR1).

BAND NUMBER	BAND NAME	BAND WIDTH (nm)
B1	Red	620 - 670
B2	NIR	841 - 876
B3	Blue	459 - 479
B4	Green	545 - 565
B5	NIR2	1230 - 1250
B6	SWIR1	1628 - 1652
B&	SWIR2	2105 - 2155

---

SR snapshots

These scripts will help you get started making snapshots with two different MODIS surface reflectance (SR) products. The eight day composites help speed up processing times.

---

daily images

//  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
//  Title:        starter_MODIS_daily.js
//  Author:       Jeff Howarth
//  Last edited:  11/17/2024
//  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

var geo = require("users/jhowarth/eePatterns:modules/geo.js");

print("geo methods dictionary", geo.help);    // Prints dictionary of all tools in module.  
print("geo palettes", geo.iPalettes);         // Prints dictionary of all palettes in module. 

// // Map.centerObject(geometry, 6);

Map.setOptions('hybrid');

// ----------------------------------------------------------------------
//  Combine Terra and Aqua daily collections. 
// ----------------------------------------------------------------------

// Print metadata for spectral bands. 

print("MODIS spectra", geo.icMODIS.spectral_bands);

// Gather collections of terra and aqua daily images. 

var terra_1day = ee.ImageCollection("MODIS/061/MOD09GA");
var aqua_1day = ee.ImageCollection("MODIS/061/MYD09GA");

print(
  "MODIS",
  terra_1day.first(),
  terra_1day.size(),
  aqua_1day.first(),
  aqua_1day.size()
  )
;

// Combine daily collections. 

var combineMODIS = terra_1day
  .merge(aqua_1day)
;

print(
  "TERRA, AQUA COMBINED",
  combineMODIS.size()
  )
;

// ----------------------------------------------------------------------
//  Filter 
// ----------------------------------------------------------------------

// Define year and month of interest. 

var yoi = 2021;
var moi = 8;

// Filter collections by time and cloudy pixels.

var output = combineMODIS
  .filter(ee.Filter.calendarRange(yoi, yoi, "year"))
  .filter(ee.Filter.calendarRange(moi, moi, "month"))
  .map(geo.icMODIS.maskClouds_1day)                   // Mask cloudy pixels
  .map(geo.icMODIS.renameSpectralBands)               // Rename bands because they have weird names.
  .median()
  .multiply(0.0001)                                   // Apply scalar after flattening collection.
;

print("OUTPUTS", output);


// ----------------------------------------------------------------------
// Display
// ----------------------------------------------------------------------

var viz = {

  bands: ['R', 'G', 'B'],
  min: [0.01, 0.02, 0.0],
  max: [0.25, 0.25, 0.175],
  gamma: 1.2,

};

Map.addLayer(output, viz, 'MODIS imagery');


// ------------------------------------------------------------------------
//  Chart histogram for a selected Image band.  
// ------------------------------------------------------------------------

// Select a band in viz dictionary to chart. 

var select_band = output.select(viz.bands[0]);

// Get AOI from map extent.

var aoi = geo.uiMap.getAOIfromMapExtent();

// Get scale from map extent.

var scale =  Map.getScale();

// Make and print histogram.

var histogram = geo.iCart.iHistogram(
    select_band, 
    scale,
    aoi                 
);

print("Histogram of selected band", histogram);

---

8 day composites

//  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
//  Title:        starter_MODIS_8day_composites.js
//  Author:       Jeff Howarth
//  Last edited:  10/18/2023
//
//  Starter for MODIS collection. 
//  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

var geo = require("users/jhowarth/eePatterns:modules/geo.js");

print("geo methods dictionary", geo.help);    // Prints dictionary of all tools in module.  
print("geo palettes", geo.iPalettes);         // Prints dictionary of all palettes in module. 

Map.setOptions('hybrid');


// ----------------------------------------------------------------------
//  Combine Terra and Aqua daily collections. 
// ----------------------------------------------------------------------

// Print metadata for spectral bands. 

print("MODIS spectra", geo.icMODIS.spectral_bands);

// Gather collections of terra and aqua 8 day averages. 

var terra_8day = ee.ImageCollection("MODIS/061/MOD09A1");
var aqua_8day = ee.ImageCollection("MODIS/061/MYD09A1");

print(
  "MODIS",
  terra_8day.first(),
  terra_8day.size(),
  aqua_8day.first(),
  aqua_8day.size()
  )
;

// Combine daily collections. 

var combineMODIS = terra_8day
  .merge(aqua_8day)
;

print(
  "TERRA, AQUA COMBINED",
  combineMODIS.size()
  )
;

// ----------------------------------------------------------------------
//  Filter collection
// ----------------------------------------------------------------------

// Define year and month of interest. 

var yoi = 2021;
var moi = 8;

// Filter collections by time and cloudy pixels.

var output = combineMODIS
  .filter(ee.Filter.calendarRange(yoi, yoi, "year"))
  .filter(ee.Filter.calendarRange(moi, moi, "month"))
  .map(geo.icMODIS.maskClouds_8day)                   // Mask cloudy pixels
  .map(geo.icMODIS.renameSpectralBands)               // Rename bands because they have weird names.
  .median()
  .multiply(0.0001)                                   // Apply scalar after flattening collection.
;

print("OUTPUTS", output);


// ----------------------------------------------------------------------
// Display
// ----------------------------------------------------------------------

var viz = {

  bands: ['R', 'G', 'B'],
  min: [0.01, 0.02, 0.0],
  max: [0.25, 0.25, 0.175],
  gamma: 1.2,

};

Map.addLayer(output, viz, 'MODIS imagery');


// ------------------------------------------------------------------------
//  Chart histogram for a selected Image band.  
// ------------------------------------------------------------------------

// Select a band in viz dictionary to chart. 

var select_band = output.select(viz.bands[0]);

// Get AOI from map extent.

var aoi = geo.uiMap.getAOIfromMapExtent();

// Get scale from map extent.

var scale =  Map.getScale();

// Make and print histogram.

var histogram = geo.iCart.iHistogram(
    select_band, 
    scale,
    aoi                 
);

print("Histogram of selected band", histogram);

---

SR time series

These scripts will help you get started with time series analysis. We use the eight-day composites to help speed up processing times.

basic time series

The script below compiles a collection (rather than a flat image) and then charts all spectral bands over the duration of the collection.

//  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
//  Title:        starter_MODIS_8day_time_series.js
//  Author:       Jeff Howarth
//  Last edited:  10/18/2023
//
//  Starter for MODIS time series. 
//  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

var geo = require("users/jhowarth/eePatterns:modules/geo.js");

print("geo methods dictionary", geo.help);    // Prints dictionary of all tools in module.  
print("geo palettes", geo.iPalettes);         // Prints dictionary of all palettes in module. 

Map.setOptions('hybrid');

// ----------------------------------------------------------------------
//  Combine Terra and Aqua daily collections. 
// ----------------------------------------------------------------------

// Print metadata for spectral bands. 

print("MODIS spectra", geo.icMODIS.spectral_bands);

// Gather collections of terra and aqua 8 day averages. 

var terra_8day = ee.ImageCollection("MODIS/061/MOD09A1");
var aqua_8day = ee.ImageCollection("MODIS/061/MYD09A1");

print(
  "MODIS",
  terra_8day.first(),
  terra_8day.size(),
  aqua_8day.first(),
  aqua_8day.size()
  )
;

// Combine daily collections. 

var combineMODIS = terra_8day
  .merge(aqua_8day)
;

print(
  "TERRA, AQUA COMBINED",
  combineMODIS.size()
  )
;

// ----------------------------------------------------------------------
//  Filter collection
// ----------------------------------------------------------------------

// Define year and month of interest. 

var yoi = 2023;

// Filter collections by time and cloudy pixels.

var output = combineMODIS
  .filter(ee.Filter.calendarRange(yoi, yoi, "year"))
  .map(geo.icMODIS.maskClouds_8day)                   // Mask cloudy pixels
  .map(geo.icMODIS.renameSpectralBands)               // Rename bands because they have weird names.
;

print("OUTPUT COLLECTION", output);


// ----------------------------------------------------------------------
//  Display image from collection as Map layer.  
// ----------------------------------------------------------------------

var viz = {

  bands: ['R', 'G', 'B'],
  min: [0.01, 0.02, 0.0],
  max: [0.25, 0.25, 0.175],
  gamma: 1.2,

};

// Define display image 

var display_image = output    // time series collection
  .median()                   // flatten image
  .multiply(0.0001)           // apply scalar for reflectance values  
;          

Map.addLayer(display_image, viz, 'MODIS imagery');


// // ------------------------------------------------------------------------
// //  Chart histogram for a selected Image band.  
// // ------------------------------------------------------------------------

// // Select a band in viz dictionary to chart. 

// var select_band = display_image.select(viz.bands[0]);

// // Get AOI from map extent.

// var aoi = geo.uiMap.getAOIfromMapExtent();

// // Get scale from map extent.

// var scale =  Map.getScale();

// // Make and print histogram.

// var histogram = geo.iCart.iHistogram(
//     select_band, 
//     scale,
//     aoi                 
// );

// print("Histogram of selected band", histogram);

// ------------------------------------------------------------------------
//  Define regions of interest.  
// ------------------------------------------------------------------------

// Gather regions from a feature collection.  

var regions = ee.FeatureCollection("FAO/GAUL/2015/level2");

// Define a point of interest with geometry tools.

var geometry = ee.Geometry.Point([-119.72687261495858, 34.42223412451513]);

// Select region of interest with poi.

var regions_select = regions.filterBounds(geometry);

// ------------------------------------------------------------------------
//  Display regions of interest as map layers.
// ------------------------------------------------------------------------

var strokes = geo.fcCart.paintStrokes(regions, "white", 0.5);

Map.addLayer(strokes, {}, "Region outlines");

var strokes_select = geo.fcCart.paintStrokes(regions_select, "yellow", 2);

Map.addLayer(strokes_select, {}, "Selected region outlines");

// -------------------------------------------------------------
//  Initialize panel for time series chart. 
// -------------------------------------------------------------

var panel_chart = geo.icIntervals.initializePanelForChart('bottom-left');

Map.add(panel_chart);

// Define parameters for time series chart.

var parameters = {
  collection: output,
  reducer: ee.Reducer.mean(),
  image_scale: 500,
  // interval_unit: "month",          // Comment out to chart by default "system:time_start"
  panel: panel_chart,
  roi: regions_select
};

// Chart time series with parameters. 

geo.icIntervals.chartTimeSeries(parameters);

---

time series of spectral index

The script below will compute a spectral index (NDVI) for each image in the time series and then chart the index over duration of the collection.

//  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
//  Title:        starter_MODIS_8day_time_series_with_ndvi.js
//  Author:       Jeff Howarth
//  Last edited:  10/18/2023
//
//  Starter for MODIS time series. 
//  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

var geo = require("users/jhowarth/eePatterns:modules/geo.js");

print("geo methods dictionary", geo.help);    // Prints dictionary of all tools in module.  
print("geo palettes", geo.iPalettes);         // Prints dictionary of all palettes in module. 

Map.setOptions('hybrid');

// ----------------------------------------------------------------------
//  Combine Terra and Aqua daily collections. 
// ----------------------------------------------------------------------

// Print metadata for spectral bands. 

print("MODIS spectra", geo.icMODIS.spectral_bands);

// Gather collections of terra and aqua 8 day averages. 

var terra_8day = ee.ImageCollection("MODIS/061/MOD09A1");
var aqua_8day = ee.ImageCollection("MODIS/061/MYD09A1");

print(
  "MODIS",
  terra_8day.first(),
  terra_8day.size(),
  aqua_8day.first(),
  aqua_8day.size()
  )
;

// Combine daily collections. 

var combineMODIS = terra_8day
  .merge(aqua_8day)
;

print(
  "TERRA, AQUA COMBINED",
  combineMODIS.size()
  )
;

// ----------------------------------------------------------------------
//  Filter collection
// ----------------------------------------------------------------------


// Filter collections by cloudy pixels.

var output = combineMODIS
  // .filter(ee.Filter.calendarRange(yoi, yoi, "year"))
  .map(geo.icMODIS.maskClouds_8day)                   // Mask cloudy pixels
//   .map(geo.icMODIS.maskWater_8day)                    // Mask water pixels. 
  .map(geo.icMODIS.renameSpectralBands)               // Rename bands because they have weird names.
;

print("OUTPUT COLLECTION", output);


// ----------------------------------------------------------------------
//  Display image from collection as Map layer.  
// ----------------------------------------------------------------------

var viz = {

  bands: ['R', 'G', 'B'],
  min: [0.01, 0.02, 0.0],
  max: [0.25, 0.25, 0.175],
  gamma: 1.2,

};

// Define display image 

var display_image = output    // time series collection
  .median()                   // flatten image
  .multiply(0.0001)           // apply scalar for reflectance values  
;          

Map.addLayer(display_image, viz, 'MODIS imagery', false);


// // ------------------------------------------------------------------------
// //  Chart histogram for a selected Image band.  
// // ------------------------------------------------------------------------

// // Select a band in viz dictionary to chart. 

// var select_band = display_image.select(viz.bands[0]);

// // Get AOI from map extent.

// var aoi = geo.uiMap.getAOIfromMapExtent();

// // Get scale from map extent.

// var scale =  Map.getScale();

// // Make and print histogram.

// var histogram = geo.iCart.iHistogram(
//     select_band, 
//     scale,
//     aoi                 
// );

// print("Histogram of selected band", histogram);


// ----------------------------------------------------------------------
//  Calculate spectral index for each image in the collection.  
// ----------------------------------------------------------------------

// Write computation as a function.  

var computeND = function(image) {

    var si = image.normalizedDifference(['N', 'R']).rename('NDVI');

    return image.addBands(si);

  };

// Map function over the collection.  

var output_with_si = output.map(computeND);

print("MAP NDVI", output.first(), output_with_si.first());

// Display spectral index image from collection as layer on Map.

var display_image_si = output_with_si     // time series collection
  .median()                               // flatten image
  .select("NDVI")
; 

Map.addLayer(display_image_si, {min:-0.8, max:0.8, palette: geo.iPalettes.iDrought}, "Image with spectral index");

// ------------------------------------------------------------------------
//  Define regions of interest.  
// ------------------------------------------------------------------------

// Gather regions from a feature collection.  

var regions = ee.FeatureCollection("FAO/GAUL/2015/level2");

// Define a point of interest with geometry tools.

var geometry = ee.Geometry.Point([-119.72687261495858, 34.42223412451513]);

// Select region of interest with poi.

var regions_select = regions.filterBounds(geometry);

// ------------------------------------------------------------------------
//  Display regions of interest as map layers.
// ------------------------------------------------------------------------

var strokes = geo.fcCart.paintStrokes(regions, "white", 0.5);

Map.addLayer(strokes, {}, "Region outlines");

var strokes_select = geo.fcCart.paintStrokes(regions_select, "yellow", 2);

Map.addLayer(strokes_select, {}, "Selected region outlines");

// -------------------------------------------------------------
//  Initialize panel for time series chart. 
// -------------------------------------------------------------

var panel_chart = geo.icIntervals.initializePanelForChart('bottom-left');

Map.add(panel_chart);

// Define parameters for time series chart.

var parameters = {
  collection: output_with_si.select('NDVI'),
  reducer: ee.Reducer.mean(),
  image_scale: 500,
  // interval_unit: "month",          // Comment out to chart by default "system:time_start"
  panel: panel_chart,
  roi: regions_select
};

// Chart time series with parameters. 

geo.icIntervals.chartTimeSeries(parameters);

---

This work is licensed under CC BY-NC-SA 4.0