How are pixels included in a weighted reducer?
Weighted reducers (e.g. ee.Reducer.mean () ): pixels are included if at least (approximately) 0.5% of the pixel is in the region and the image’s mask is non-zero; their weight is the minimum of the image’s mask and the (approximate) fraction of the pixel covered by the region. The maxPixels parameter is needed to get the computation to succeed.
How to get statistics of an image region?
To get statistics of pixel values in a region of an ee.Image, use image.reduceRegion () . This reduces all the pixels in the region (s) to a statistic or other compact representation of the pixel data in the region (e.g. histogram).
How to reduce a region in Google Earth?
The region over which to reduce is shown in white. Note that in this example the reduction is specified by providing the reducer ( ee.Reducer.mean () ), the geometry ( region.geometry () ), the scale (30 meters) and maxPixels for the maximum number of pixels to input to the reducer. A scale should always be specified in reduceRegion () calls.
Why is scale specified in reduceregion ( ) call?
A scale should always be specified in reduceRegion () calls. This is because in complex processing flows, which may involve data from different sources with different scales, the scale of the output will not be unambiguously determined from the inputs. In that case, the scale defaults to 1 degree, which generally produces unsatisfactory results.
What is result of reduceregion with grouped reducer?
The result of reduceRegion () with a grouped reducer is a dictionary of dictionaries for each class. The top level dictionary has a single key named ‘ groups ‘. To extract the individual dictionaries and get properly formatted results, we must do a little post-processing.
What’s the default number of pixels in reduceregion?
The default maximum number of pixels in reduceRegion () is 10 million. This error message indicates that the Congo Republic covers about 383 million Landsat pixels. Luckily, reduceRegion () takes many parameters, one of which ( maxPixels) lets you control how many pixels are used in the computation.