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How to set scale in Google Earth Engine?
See this page for more information about how Earth Engine handles scale. There are two ways to set the scale: by specifying the scale parameter, or by specifying a CRS and CRS transform. (See the glossary for more information about CRS’s and CRS transforms). For example, the meanDictionary reduction (above) is equivalent to the following:
How to calculate region in Google Earth Engine?
// Load input imagery: Landsat 7 5-year composite. // Load an input region: Sierra Nevada. // Reduce the region. The region parameter is the Feature geometry. // The result is a Dictionary. Print it. To force the computation, it suffices to print the result, which the Code Editor will display as a Dictionary in the console.
How are pixels determined to be in the region?
Pixels are determined to be in the region (and weighted) according to the following rules, applied in the specified scale and projection: Unweighted reducers (e.g. ee.Reducer.count () or ee.Reducer.mean ().unweighted () ): pixels are included if their centroid is in the region and the image’s mask is non-zero.
How is the scale determined in Earth Engine?
In general, specifying the scale is sufficient and results in more readable code. Earth Engine determines which pixels to input to the reducer by first rasterizing the region. If a scale is specified without a CRS, the region is rasterized in the image’s native projection scaled to the specified resolution.
How are reprojections performed in Google Earth Engine?
The second reprojection is implicit, performed by Earth Engine automatically in order to display the result on the map. Also observe that the information about what projection to use propagates back from the request to the input. Figure 2. Flow chart of operations corresponding to the reprojection of a MODIS image in the Code Editor map.
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 to normalize projection in Google Earth Engine?
When you display images in the Code Editor, inputs are requested in maps mercator. Consider the following simple operation on a MODIS image, which has a sinusoidal projection: // The input image has a SR-ORG:6974 (sinusoidal) projection. // Normalize the image and add it to the map.
How to extract data from Google Earth Engine?
The most efficient way to get the data out of Earth Engine is to use Export.image instead, then convert the downloaded GeoTIFF to suit your R program. However, since this dataset is very small, downloading it as a CSV will work fine, and the tool for that is ee.Image.sample which converts a region of an Image to a FeatureCollection.
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.