Load Landsat Collection

Landsat, a joint program of the USGS and NASA, has been observing the Earth continuously from 1972 through the present day. Today the Landsat satellites image the entire Earth’s surface at a 30-meter resolution about once every two weeks, including multispectral and thermal data.

Landsat data is available in Earth Engine in its raw form, as Surface Reflectance, TOA-corrected reflectance, and in various ready-to-use computed products such as NDVI and EVI vegetation indices.

Note

In this course we will only work with Landsat Collection 2 that marks the second major reprocessing effort on the Landsat archive by the USGS that results in several data product improvements over Collection 1 that harness recent advancements in data processing and algorithm development.

Satellite	Landsat 5	Landsat 7	Landsat 8	Landsat 9
Instrument	Multispectral Scanner (MSS), Thematic Mapper (TM)	Enhanced Thematic Mapper (ETM+)	Operational Land Imager (OLI), Thermal Infrared Sensor (TIRS)	OLI-2, TIRS-2
Number of bands	10	10	10	10
Spatial resolution	30m x 30m	30m x 30m	30m x 30m	30m x 30m
Temporal resolution	16 days	16 days	16 days	16 days
Temporal range	1984 - 2012	1999 - Present	2013 - Present	2021 - Present
Google Earth Engine collection	Dataset	Dataset	Dataset	Not available

Let’s define which datasets we will work with.

// Load USGS Landsat 5 Level 2, Collection 2, Tier 1
var landsat_5 = ee.ImageCollection("LANDSAT/LT05/C02/T1_L2")

// Load USGS Landsat 7 Level 2, Collection 2, Tier 1
var landsat_7 = ee.ImageCollection("LANDSAT/LE07/C02/T1_L2")

// Load USGS Landsat 8 Level 2, Collection 2, Tier 1
var landsat_8 = ee.ImageCollection('LANDSAT/LC08/C02/T1_L2')

Filter Landsat data

// Define time period
var startDate = '2019-01-01'
var endDate   = '2019-12-31'

var roi = ee.FeatureCollection("users/nicolasdeffense/extent_roi_32631")

// Select Landsat 8 images in area of interest and time period
var l8_filter = landsat_8
                .filterDate(startDate, endDate)
                .filterBounds(roi)

Apply scaling factors

A scale factor must be applied to both Collection 1 and Collection 2 Landsat Level-2 surface reflectance and surface temperature products before using the data.
Landsat Collection 2 have the following scale factors, fill values, data type, and valid range.

Science Product	Scale Factor	Fill Value	Data Type	Valid Range
Surface Reflectance	0.0000275 + -0.2	0	Unsigned 16-bit integer	1-65455
Surface Temperature	0.00341802 + 149.0	0	Unsigned 16-bit integer	1-65455

Note

Examples for scaling Landsat Collection 2 Level-2 science products
Landsat Collection 2 surface reflectance has a scale factor of 0.0000275 and an additional offset of -0.2 per pixel.
For example, a pixel value of 18,639 is multiplied by 0.0000275 for the scale factor and then -0.2 is added for the additional offset to get a reflectance value of 0.313 after the scale factor is applied.

// Applies scaling factors.
function applyScaleFactors(image) {
  var opticalBands = image.select('SR_B.').multiply(0.0000275).add(-0.2)
  var thermalBands = image.select('ST_B.*').multiply(0.00341802).add(149.0)
  return image.addBands(opticalBands, null, true)
              .addBands(thermalBands, null, true)
}

var l8_filter = l8_filter.map(applyScaleFactors)