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Why does Google Earth Engine require a projection?
Only for output that’s ambiguous will Earth Engine require you to specify a projection and/or scale. Ambiguity can result from reducing an ImageCollection containing images with different projections (i.e. creating a composite ).
Why is my projection invalid in Earth Engine?
If you try to use an image like this in a computation, you may see an error like: The default WGS84 projection is invalid for aggregations. Specify a scale or crs & crs_transform. Generally, an aggregation at 1-degree scale is not desired or intended, so Earth Engine gives this friendly reminder to provide a complete specification for the output.
What is an example of an error in Google Earth Engine?
// Load a Sentinel-2 image. // Error: Image.select: Pattern ‘nonBand’ did not match any bands. In this example, the error informs you that there is no band named nonBand. The possibly obvious solution is to specify a band name that does exist.
What happens if you have too much data in Google Earth Engine?
If the scale you specified in the reproject () call is much smaller than the zoom level of the map, Earth Engine will request all the inputs at very small scale, over a very wide spatial extent. This can result in much too much data being requested at once and lead to an error.
How does reduceresolution work in Google Earth Engine?
The weights of pixels used during the reduceResolution () aggregation process are based on the overlap between the smaller pixels being aggregated and the larger pixels specified by the output projection. This is illustrated in Figure 4. Figure 4.
How to resample an image in Google Earth?
For this reason, call resample () directly on the input image. Consider the following simple example: // Load a Landsat image over San Francisco, California, UAS. // Set display and visualization parameters. // Display the Landsat image using the default nearest neighbor resampling.
How does resampling work in Google Earth Engine?
Specifically, when one of these methods is applied to an input image, any required reprojection of the input will be done using the indicated resampling or aggregation method. resample () causes the indicated resampling method ( ‘bilinear’ or ‘bicubic’) to be used at the next reprojection.
Which is an example of Google Earth Engine?
Suppose, for example, you reproject something and add it to the map. If the scale you specified in the reproject () call is much smaller than the zoom level of the map, Earth Engine will request all the inputs at very small scale, over a very wide spatial extent.
How are pixels used in reduceresolution in Google Earth?
The weights of pixels used during the reduceResolution () aggregation process are based on the overlap between the smaller pixels being aggregated and the larger pixels specified by the output projection. This is illustrated in Figure 4. Figure 4. Input pixels (black) and output pixel (blue) for reduceResolution () .
When to use resampling instead of reprojection?
Suppose that instead of resampling during reprojection, your goal is to aggregate pixels to larger pixels in a different projection. This is useful when comparing image datasets at different scales, for example 30-meter pixels from a Landsat-based product to coarse pixels (higher scale) from a MODIS-based product.