Page Summary
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The
ee.Image.pixelArea()function creates an image where each pixel's value represents its area in square meters. -
This function returns an Image with a single band named "area" and requires no arguments.
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The output can be used to calculate the area of specific conditions or features within another image.
| Usage | Returns |
|---|---|
ee.Image.pixelArea()
|
Image |
No arguments.
Examples
Code Editor (JavaScript)
// 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 );
import ee import geemap.core as geemap
Colab (Python)
# 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 )
