Gee: create a new feature and set corresponding attributes

Although patience and persistence is a painful thing, but it can gradually bring you good.—— Ovid

Patience and persistence are painful things , But it can gradually bring you benefits .—— Ovid

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One 、 problem

Earth Engine One of them Feature Is defined as GeoJSON features . say concretely ,a Feature Yes. geometry Storage Geometry object （ or null） Of properties Attributes and objects that store attributes of other attribute dictionaries .

But how in GEE Create a Feature, And assign corresponding attributes to it ？

Two 、 Function and usage

• ee.Feature()

3、 ... and 、 Examples of operation

1、 Create an empty Feature

python The code is as follows ：

# Feature Unwanted  a Geometry And you can simply wrap an attribute dictionary 
#  This situation can be applied to the analysis of data , Creating features in this way is important for exporting 
#  have Dictionary result （ for example image.reduceRegion()） Long running calculations of are very useful .
dict = {'foo':ee.Number(8).add(88), 'bar':'nihao'}
numFeature = ee.Feature(None, dict)
numFeature.getInfo()

2、 Create a Geometry And attribute Feature

python The code is as follows ：

# Earth Engine  Medium AFeature Is defined as  GeoJSON  features . say concretely ,aFeature Yes. geometry Storage  Geometry object （ or  null） Of properties Attributes and objects that store attributes of other attribute dictionaries .
#  To create a  a Feature, Please provide the constructor  Geometry  and （ Optional ） Dictionary of other attributes 
polygon = ee.Geometry.Polygon([[-35, -10], [35, -10], [35, 10], [-35, 10], [-35, -10]])
polyFeature = ee.Feature(polygon, {'foo':42, 'bar':'tart'})

Map = geemap.Map()
Map.addLayer(polyFeature, {}, 'Feature')
Map

  give the result as follows ：

 3、 by Feature Add attributes and queries

python The code is as follows ：

#  Every Feature There is one. Geometry Stored in  geometry The master node in the attribute . Other geometry can be stored in other attributes . 
# Geometry There are also methods such as intersections and buffers , Feature To facilitate access to the main object Geometry, Apply the operation and set the result to the new main object Geometry.
#  The result will be preserved Feature Call all other properties of this method . There are also some ways to get and set Feature. 
feature = ee.Feature(ee.Geometry.Point([-122.22599, 37.17605])) \
    .set('genus', 'Pine') \
    .set('species', 'Green')
prop1 = feature.get('species')
print(prop1.getInfo())

#  Set new properties 
feature = feature.set('presence', 1)

prop2 = feature.get('presence')
print(prop2.getInfo())

Four 、 Summary

1. utilize ee.Feature() It can be easily realized Feature The creation of , use set Method to add the attribute dictionary to the attribute , utilize get() Method to query the corresponding attribute
2. You need to understand how to create an empty Feature Methods , Use this method to combine ee.reduceRegion() It can flexibly realize the processing and analysis of time series results .

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Reference resources ：

1. https://developers.google.com/earth-engine/apidocs/ee-feature?hl=en
2. https://developers.google.com/earth-engine/guides/features
3. https://github.com/giswqs/earthengine-py-notebooks/blob/master/FeatureCollection/creating_feature.ipynb