Python处特定经纬度点的输出值

Question

由于我的解释较短，我在 2020/01/20 编辑了这个问题。抱歉原来的回答者。

我想要特定纬度/经度波段的TOA反射率值。我可以通过下面的代码用 javascript 做到这一点，但我不能用 python 做同样的事情。我很高兴能得到你未来的帮助。

var start = '2018-01-01'
var end = '2018-01-16'
var lon =  134.01
var lat = 34.04
var p = ee.Geometry.Point(lon, lat) 

var imageCollection = ee.ImageCollection('LANDSAT/LC08/C01/T1_TOA')
  .filterDate(start, end) 
  .filterBounds(p) 

var im1 = imageCollection
  .first()
var image = ee.Image(im1);

// Extract the data 
var data_b1 = im1.select("B1").reduceRegion(ee.Reducer.mean(),p,10).get("B1")
print('B1 T1_TOA: ', data_b1)

Javascript 输出是这个 TOA 反射率：

B1 T1_TOA: 
0.25892749428749084

但在 Python 时效果不佳。输出为 ComputedObject，但不包含 TOA 反射率值。

import ee
ee.Initialize()

start = '2018-01-01'
end = '2018-01-16'
lon = 134.01
lat = 34.04
p = ee.Geometry.Point([lon, lat])

imageCollection = ee.ImageCollection('LANDSAT/LC08/C01/T1_TOA').filterDate(start, end).filterBounds(p)
im1 = imageCollection.first()
data_b1 = im1.select("B1").reduceRegion(ee.Reducer.mean(),p,10).get("B1")

print(data_b1)

输出低于 json，不包括 TOA 反射率值“0.25892749428749084”：

ee.ComputedObject({
  "type": "Invocation",
  "arguments": {
    "dictionary": {
      "type": "Invocation",
      "arguments": {
        "image": {
          "type": "Invocation",
          "arguments": {
            "input": {
              "type": "Invocation",
              "arguments": {
                "collection": {
                  "type": "Invocation",
                  "arguments": {
                    "collection": {
                      "type": "Invocation",
                      "arguments": {
                        "collection": {
                          "type": "Invocation",
                          "arguments": {
                            "id": "LANDSAT/LC08/C01/T1_TOA"
                          },
                          "functionName": "ImageCollection.load"
                        },
                        "filter": {
                          "type": "Invocation",
                          "arguments": {
                            "rightField": "system:time_start",
                            "leftValue": {
                              "type": "Invocation",
                              "arguments": {
                                "start": "2018-01-01",
                                "end": "2018-01-16"
                              },
                              "functionName": "DateRange"
                            }
                          },
                          "functionName": "Filter.dateRangeContains"
                        }
                      },
                      "functionName": "Collection.filter"
                    },
                    "filter": {
                      "type": "Invocation",
                      "arguments": {
                        "leftField": ".all",
                        "rightValue": {
                          "type": "Invocation",
                          "arguments": {
                            "geometry": {
                              "type": "Point",
                              "coordinates": [
                                134.01,
                                34.04
                              ]
                            }
                          },
                          "functionName": "Feature"
                        }
                      },
                      "functionName": "Filter.intersects"
                    }
                  },
                  "functionName": "Collection.filter"
                }
              },
              "functionName": "Collection.first"
            },
            "bandSelectors": [
              "B1"
            ]
          },
          "functionName": "Image.select"
        },
        "reducer": {
          "type": "Invocation",
          "arguments": {},
          "functionName": "Reducer.mean"
        },
        "geometry": {
          "type": "Point",
          "coordinates": [
            134.01,
            34.04
          ]
        },
        "scale": 10
      },
      "functionName": "Image.reduceRegion"
    },
    "key": "B1"
  },
  "functionName": "Dictionary.get"
})

Answer 1

我发现您的 python 代码有效。首先，我在此 link https://earthengine.google.com 注册了 Google Earth Engine。然后我在 Google Colab 上安装 earthengine-api 包。当您执行代码时，您会看到一条消息，要求您授权 Earth Engine 所需的访问权限。请按照说明进行操作。

Python代码：

import ee

# Trigger the authentication flow.
ee.Authenticate()

# Initialize the library.
ee.Initialize()

lat = 35.1000
lon = 135.2000
p = ee.Geometry.Point([lon, lat])
start = '2017-11-21'
end = '2017-12-30'
imageCollection = ee.ImageCollection('LANDSAT/LC08/C01/T1').filterDate(start, end).filterBounds(p)
im1 = imageCollection.sort('CLOUD_COVER', True).first()
data_b1 = im1.select("B1").reduceRegion(ee.Reducer.mean(),p,10).get("B1")

print(data_b1)

执行代码时的消息提示示例

输出结果。

Answer 2

您需要将服务器端对象转换为客户端对象。尝试：

print(data_b1.getInfo())

有关使用 Python API 打印 Earth Engine 对象的更多信息，请参阅此 guide。

Python处特定经纬度点的输出值

Output value of a specific latitude and longitude point at Python

python

google-earth-engine