AI-generated Key Takeaways
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This function calculates aspect in degrees from a terrain Digital Elevation Model (DEM).
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Missing values will occur around the edges of an image because the local gradient is computed using 4-connected neighbors.
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The function
ee.Terrain.aspect(input)takes an elevation image as input and returns an Image. -
The returned aspect units are in degrees, where 0 is North, 90 is East, 180 is South, and 270 is West.
The local gradient is computed using the 4-connected neighbors of each pixel, so missing values will occur around the edges of an image.
| Usage | Returns |
|---|---|
ee.Terrain.aspect(input)
|
Image |
| Argument | Type | Details |
|---|---|---|
input
|
Image | An elevation image, in meters. |
Examples
Code Editor (JavaScript)
// A digital elevation model. var dem = ee . Image ( 'NASA/NASADEM_HGT/001' ). select ( 'elevation' ); // Calculate slope. Units are degrees, range is [0,90). var slope = ee . Terrain . slope ( dem ); // Calculate aspect. Units are degrees where 0=N, 90=E, 180=S, 270=W. var aspect = ee . Terrain . aspect ( dem ); // Display slope and aspect layers on the map. Map . setCenter ( - 123.457 , 47.815 , 11 ); Map . addLayer ( slope , { min : 0 , max : 89.99 }, 'Slope' ); Map . addLayer ( aspect , { min : 0 , max : 359.99 }, 'Aspect' ); // Use the ee.Terrain.products function to calculate slope, aspect, and // hillshade simultaneously. The output bands are appended to the input image. // Hillshade is calculated based on illumination azimuth=270, elevation=45. var terrain = ee . Terrain . products ( dem ); print ( 'ee.Terrain.products bands' , terrain . bandNames ()); Map . addLayer ( terrain . select ( 'hillshade' ), { min : 0 , max : 255 }, 'Hillshade' );;
import ee import geemap.core as geemap
Colab (Python)
# A digital elevation model. dem = ee . Image ( 'NASA/NASADEM_HGT/001' ) . select ( 'elevation' ) # Calculate slope. Units are degrees, range is [0,90). slope = ee . Terrain . slope ( dem ) # Calculate aspect. Units are degrees where 0=N, 90=E, 180=S, 270=W. aspect = ee . Terrain . aspect ( dem ) # Display slope and aspect layers on the map. m = geemap . Map () m . set_center ( - 123.457 , 47.815 , 11 ) m . add_layer ( slope , { 'min' : 0 , 'max' : 89.99 }, 'Slope' ) m . add_layer ( aspect , { 'min' : 0 , 'max' : 359.99 }, 'Aspect' ) # Use the ee.Terrain.products function to calculate slope, aspect, and # hillshade simultaneously. The output bands are appended to the input image. # Hillshade is calculated based on illumination azimuth=270, elevation=45. terrain = ee . Terrain . products ( dem ) display ( 'ee.Terrain.products bands' , terrain . bandNames ()) m . add_layer ( terrain . select ( 'hillshade' ), { 'min' : 0 , 'max' : 255 }, 'Hillshade' ) m
