ee.Image.pixelArea

 // Create a pixel area image. Pixel values are square meters based on 
 // a given CRS and scale (or CRS transform). 
 var 
  
 pixelArea 
  
 = 
  
 ee 
 . 
 Image 
 . 
 pixelArea 
 (); 
 // The default projection is WGS84 with 1-degree scale. 
 print 
 ( 
 'Pixel area default projection' 
 , 
  
 pixelArea 
 . 
 projection 
 ()); 
 // When inspecting the output in the Code Editor map, the scale of analysis is 
 // determined by the zoom level. As you zoom in and out, you'll notice that the 
 // area of the clicked pixel changes. To set a specific pixel scale when 
 // performing a computation, provide an argument to the `scale` or 
 // `crsTransform` parameters whenever a function gives you the option. 
 Map 
 . 
 addLayer 
 ( 
 pixelArea 
 , 
  
 null 
 , 
  
 'Pixel area for inspection' 
 , 
  
 false 
 ); 
 // The "area" band produced by the `pixelArea` function can be useful for 
 // calculating the area of a certain condition of another image. For example, 
 // here we use the sum reducer to determine the area above 2250m in the North 
 // Cascades ecoregion, according to a 30m digital elevation model. 
 // Import a DEM and subset the "elevation" band. 
 var 
  
 elev 
  
 = 
  
 ee 
 . 
 Image 
 ( 
 'NASA/NASADEM_HGT/001' 
 ). 
 select 
 ( 
 'elevation' 
 ); 
 // Define a high elevation mask where pixels with elevation greater than 2250m 
 // are set to 1, otherwise 0. 
 var 
  
 highElevMask 
  
 = 
  
 elev 
 . 
 gt 
 ( 
 2250 
 ); 
 // Apply the high elevation mask to the pixel area image. 
 var 
  
 highElevArea 
  
 = 
  
 pixelArea 
 . 
 updateMask 
 ( 
 highElevMask 
 ); 
 // Import an ecoregion feature collection and filter it by ecoregion name. 
 var 
  
 ecoregion 
  
 = 
  
 ee 
 . 
 FeatureCollection 
 ( 
 'RESOLVE/ECOREGIONS/2017' 
 ) 
  
 . 
 filter 
 ( 
 'ECO_NAME == "North Cascades conifer forests"' 
 ); 
 // Display the ecoregion and high elevation area. 
 Map 
 . 
 setCenter 
 ( 
 - 
 121.127 
 , 
  
 48.389 
 , 
  
 7 
 ); 
 Map 
 . 
 addLayer 
 ( 
 ecoregion 
 , 
  
 null 
 , 
  
 'North Cascades ecoregion' 
 ); 
 Map 
 . 
 addLayer 
 ( 
 highElevArea 
 . 
 clip 
 ( 
 ecoregion 
 ), 
  
 { 
 palette 
 : 
  
 'yellow' 
 }, 
  
 'High elevation area' 
 ); 
 // Sum the area of high elevation pixels in the North Cascades ecoregion. 
 var 
  
 area 
  
 = 
  
 highElevArea 
 . 
 reduceRegion 
 ({ 
  
 reducer 
 : 
  
 ee 
 . 
 Reducer 
 . 
 sum 
 (), 
  
 geometry 
 : 
  
 ecoregion 
 , 
  
 crs 
 : 
  
 elev 
 . 
 projection 
 (), 
  
 // DEM coordinate reference system 
  
 crsTransform 
 : 
  
 elev 
 . 
 projection 
 (). 
 getInfo 
 (). 
 transform 
 , 
  
 // DEM grid alignment 
  
 maxPixels 
 : 
  
 1e8 
 }); 
 // Fetch the summed area property from the resulting dictionary and convert 
 // square meters to square kilometers. 
 var 
  
 squareMeters 
  
 = 
  
 area 
 . 
 getNumber 
 ( 
 'area' 
 ); 
 var 
  
 squareKilometers 
  
 = 
  
 squareMeters 
 . 
 divide 
 ( 
 1e6 
 ); 
 print 
 ( 
 'Square meters above 2250m elevation' 
 , 
  
 squareMeters 
 ); 
 print 
 ( 
 'Square kilometers above 2250m elevation' 
 , 
  
 squareKilometers 
 ); 

 # Create a pixel area image. Pixel values are square meters based on 
 # a given CRS and scale (or CRS transform). 
 pixel_area 
 = 
 ee 
 . 
 Image 
 . 
 pixelArea 
 () 
 # The default projection is WGS84 with 1-degree scale. 
 display 
 ( 
 'Pixel area default projection' 
 , 
 pixel_area 
 . 
 projection 
 ()) 
 # When inspecting the output in the Code Editor map, the scale of analysis is 
 # determined by the zoom level. As you zoom in and out, you'll notice that the 
 # area of the clicked pixel changes. To set a specific pixel scale when 
 # performing a computation, provide an argument to the `scale` or 
 # `crsTransform` parameters whenever a function gives you the option. 
 m 
 = 
 geemap 
 . 
 Map 
 () 
 m 
 . 
 add_layer 
 ( 
 pixel_area 
 , 
 None 
 , 
 'Pixel area for inspection' 
 , 
 False 
 ) 
 # The "area" band produced by the `pixel_area` function can be useful for 
 # calculating the area of a certain condition of another image. For example, 
 # here we use the sum reducer to determine the area above 2250m in the North 
 # Cascades ecoregion, according to a 30m digital elevation model. 
 # Import a DEM and subset the "elevation" band. 
 elev 
 = 
 ee 
 . 
 Image 
 ( 
 'NASA/NASADEM_HGT/001' 
 ) 
 . 
 select 
 ( 
 'elevation' 
 ) 
 # Define a high elevation mask where pixels with elevation greater than 2250m 
 # are set to 1, otherwise 0. 
 high_elev_mask 
 = 
 elev 
 . 
 gt 
 ( 
 2250 
 ) 
 # Apply the high elevation mask to the pixel area image. 
 high_elev_area 
 = 
 pixel_area 
 . 
 updateMask 
 ( 
 high_elev_mask 
 ) 
 # Import an ecoregion feature collection and filter it by ecoregion name. 
 ecoregion 
 = 
 ee 
 . 
 FeatureCollection 
 ( 
 'RESOLVE/ECOREGIONS/2017' 
 ) 
 . 
 filter 
 ( 
 'ECO_NAME == "North Cascades conifer forests"' 
 ) 
 # Display the ecoregion and high elevation area. 
 m 
 . 
 set_center 
 ( 
 - 
 121.127 
 , 
 48.389 
 , 
 7 
 ) 
 m 
 . 
 add_layer 
 ( 
 ecoregion 
 , 
 None 
 , 
 'North Cascades ecoregion' 
 ) 
 m 
 . 
 add_layer 
 ( 
 high_elev_area 
 . 
 clip 
 ( 
 ecoregion 
 ), 
 { 
 'palette' 
 : 
 'yellow' 
 }, 
 'High elevation area' 
 ) 
 display 
 ( 
 m 
 ) 
 # Sum the area of high elevation pixels in the North Cascades ecoregion. 
 area 
 = 
 high_elev_area 
 . 
 reduceRegion 
 ( 
 reducer 
 = 
 ee 
 . 
 Reducer 
 . 
 sum 
 (), 
 geometry 
 = 
 ecoregion 
 , 
 crs 
 = 
 elev 
 . 
 projection 
 (), 
 # DEM coordinate reference system 
 crsTransform 
 = 
 elev 
 . 
 projection 
 () 
 . 
 getInfo 
 ()[ 
 'transform' 
 ], 
 # DEM grid alignment 
 maxPixels 
 = 
 1e8 
 , 
 ) 
 # Fetch the summed area property from the resulting dictionary and convert 
 # square meters to square kilometers. 
 square_meters 
 = 
 area 
 . 
 getNumber 
 ( 
 'area' 
 ) 
 square_kilometers 
 = 
 square_meters 
 . 
 divide 
 ( 
 1e6 
 ) 
 display 
 ( 
 'Square meters above 2250m elevation' 
 , 
 square_meters 
 ) 
 display 
 ( 
 'Square kilometers above 2250m elevation' 
 , 
 square_kilometers 
 )