GEE错误——image.reduceRegion is not a function

简介

image.reduceRegion is not a function

这里的主要问题是我们进行地统计分析的时候，我们的作用对象必须是单景影像，而不是影像集合

错误"image.reduceRegion is not a function" 表示你正在尝试使用reduceRegion()函数来处理图像数据，但是该函数在所使用的图像对象上并不存在。这通常发生在以下几种情况下：

你使用的图像对象并不是由Earth Engine提供的图像数据类型。只有Earth Engine提供的图像数据类型，如Image、ImageCollection等，才包含reduceRegion()函数。确保你使用的图像对象是Earth Engine提供的类型。
你使用的图像对象是一个空对象或没有加载任何数据。如果图像对象为空，那么该对象上是没有reduceRegion()函数的。请确保你加载了正确的图像数据，或者使用其他方法创建图像对象。
你使用了错误的函数名称。请检查你的代码，确保你使用的是reduceRegion()而不是其他名称类似的函数。

请根据具体情况查看你的代码，并根据上述解释进行适当的修改。

代码

var landsat = ee.ImageCollection("LANDSAT/LC08/C02/T1_L2"),
    imageVisParam = {"opacity":1,"bands":["B7","B6","B4"],"min":11451.624047549685,"max":13348.162011801593,"gamma":1},
    blore = 
    /* color: #0b4a8b */
    /* shown: false */
    /* displayProperties: [
      {
        "type": "rectangle"
      }
    ] */
    ee.Geometry.Polygon(
        [[[77.1829215561055, 13.595511689413932],
          [77.1829215561055, 12.530677550689433],
          [78.1167594467305, 12.530677550689433],
          [78.1167594467305, 13.595511689413932]]], null, false),
    pol_CO = ee.ImageCollection("COPERNICUS/S5P/OFFL/L3_CO"),
    pol_NO2 = ee.ImageCollection("COPERNICUS/S5P/OFFL/L3_NO2"),
    pol_CH4 = ee.ImageCollection("COPERNICUS/S5P/OFFL/L3_CH4"),
    pol_SO2 = ee.ImageCollection("COPERNICUS/S5P/OFFL/L3_SO2"),
    pol_O3 = ee.ImageCollection("COPERNICUS/S5P/OFFL/L3_O3");
var parks = ee.FeatureCollection('projects/ee-koushikyash/assets/Ban_parks_10ha');

var i = 1;
var bufferDis = 50

// create new buffer
var newBuffer = function(feature) {
  var geometry = feature.geometry();
  var buffer = geometry.buffer(bufferDis * i);
  // print(i)
  buffer = buffer.difference(geometry)
  var newFeature = ee.Feature(buffer, feature.toDictionary());
 
  return newFeature;
};

// subtract geometry
var subtractGeometries = function(feature1, feature2) {
  var geometry1 = feature1.geometry();
  var geometry2 = feature2.geometry();
  return geometry1.difference(geometry2);
};

var allBuffers = ee.List([])

var parks_0 = parks;
Map.addLayer(parks_0, {}, 'Buffer around Bangalore Parks ' + (0));
allBuffers = allBuffers.add(parks_0)
var prev = parks_0
var colors = ["Red", "Green", "Orange", "Yellow", "Pink"]

var total = 5;
for(var j = 0; j < total; j++){
  var parks_1 = parks.map(newBuffer)
  var temp = parks_1
  parks_1 = parks_1.map(function(f1) {
    var index = parks_1.toList(parks_1.size()).indexOf(f1)
    var f2 = ee.Feature(prev.toList(prev.size()).get(index))
    return ee.Feature(subtractGeometries(f1, f2), f1.toDictionary())
  });
  
  // changing state
  prev = temp
  i += 1
  allBuffers = allBuffers.add(parks_1)
  
  Map.addLayer(parks_1,  {color: colors[j]}, 'Buffer around Bangalore Parks ' + (i));
}

//Add pollutant images
var image_so2 = pol_SO2.filterBounds(parks)
            .filterDate('2024-01-01', '2024-01-31')
            .select('SO2_column_number_density')
            .mean()
            .clip(parks)
            
var image_no2 = pol_NO2.filterBounds(parks)
            .filterDate('2024-01-01', '2024-01-31')
            .select('NO2_column_number_density')
            .mean()
            .clip(parks)
            
            
var image_ch4 = pol_CH4.filterBounds(parks)
            .filterDate('2024-01-01', '2024-01-31')
            .select('CH4_column_volume_mixing_ratio_dry_air')
            .mean()
            .clip(parks)

var image_o3 = pol_O3.filterBounds(parks)
            .filterDate('2024-01-01', '2024-01-31')
            .select('O3_column_number_density')
            .mean()
            .clip(parks)

var image_co = pol_CO.filterBounds(parks)
            .filterDate('2024-01-01', '2024-01-31')
            .select('CO_column_number_density')
            .mean()
            .clip(parks) 
            

// Check the type of image
print("Type of image_so2:", typeof image_so2);

// Check if image_so2 is an ee.Image object
print("Is image_so2 an ee.Image?", image_so2 instanceof ee.Image);

// Check the type of park
print("Type of a park feature:", typeof parks.get(0));
print(parks.first());
// Check if a park feature is an ee.Feature object
print("Is a park feature an ee.Feature?", parks.first() instanceof ee.Feature);

// Check if the geometry method is available on a park feature
print("Does park feature have a geometry method?", parks.get(0).geometry !== undefined);

// var sampleFeature = parks.first();
// var geometry = sampleFeature.geometry();
// print("Geometry of sample feature:", geometry);

// var featureCount = parks.size();
// print("Number of features in parks:", featureCount);

// Function to calculate pollutant statistics for each park
var calculateStatistics = function(image, park) {
  var stats = image.reduceRegion({
    reducer: ee.Reducer.mean().combine({
    reducer2: ee.Reducer.minMax(),
    sharedInputs: true
    }),
    geometry: park.geometry(),
    scale: 30,
    maxPixels: 1e9
  });
  
  // Map over the stats to format them as features
  var features = ee.Feature(null, stats)
    .set('date', image.date().format('YYYY-MM-dd'))
    .set('park_name', park.get('name')); // Assuming 'name' is the property containing park names
  
  return features;
};

// Function to get statistics for all pollutants and parks
var getResults = function(parks, images) {
  var results = ee.List(images).map(function(image) {
    var stats = parks.map(function(park) {
      return calculateStatistics(image, ee.Feature(park));
    });
    return stats;
  }).flatten();
  
  return results;
};

// Function to format the results
var format = function(table) {
  var rows = table.distinct('date');
  var columns = parks.aggregate_array('name'); 
  var formattedResults = rows.map(function(row) {
    var date = row.get('date');
    var parkStats = table.filter(ee.Filter.eq('date', date));
    var values = parkStats.aggregate_array('pollutant_min', 'pollutant_max', 'pollutant_mean');
    return ee.Feature(null, values).set('date', date);
  });
  
  return formattedResults;
};

// Export to CSV function
var exportToCsv = function(table, desc, name) {
  Export.table.toDrive({
    collection: table,
    description: desc,
    fileNamePrefix: name,
    fileFormat: "CSV"
  });
};

// Assuming you have defined the pollutant images (image_so2, image_no2, etc.) and parks beforehand

// Get data for all pollutants and parks

var image_so2 = pol_SO2.filterBounds(parks)
            .filterDate('2024-01-01', '2024-01-31')
            .select('SO2_column_number_density')
            .mean()
            .clip(parks)
            
var image_no2 = pol_NO2.filterBounds(parks)
            .filterDate('2024-01-01', '2024-01-31')
            .select('NO2_column_number_density')
            .mean()
            .clip(parks)
            
            
var image_ch4 = pol_CH4.filterBounds(parks)
            .filterDate('2024-01-01', '2024-01-31')
            .select('CH4_column_volume_mixing_ratio_dry_air')
            .mean()
            .clip(parks)

var image_o3 = pol_O3.filterBounds(parks)
            .filterDate('2024-01-01', '2024-01-31')
            .select('O3_column_number_density')
            .mean()
            .clip(parks)

var image_co = pol_CO.filterBounds(parks)
            .filterDate('2024-01-01', '2024-01-31')
            .select('CO_column_number_density')
            .mean()
            .clip(parks) 
            
var images = [image_so2, image_no2, image_ch4, image_o3, image_co]; 

//checking the type of iamges array
print(images);

var results = getResults(parks, images);

// Format the results
var formattedResults = format(results);

// Export the formatted results to CSV
exportToCsv(formattedResults, "PollutantStatistics", "pollutant_stats");

正确解析

这里的正确思路是我们需要进行分析，也就是说我们的作用对象是影像，而非影像集合，所以这里我们不能混淆这里两个概念，首先看一下两个函数的差异：

ee.Image(args)

An object to represent an Earth Engine image. This constructor accepts a variety of arguments:

A string: an EarthEngine asset id,
A string and a number: an EarthEngine asset id and version,
A number or ee.Array: creates a constant image,
A list: creates an image out of each list element and combines them into a single image,
An ee.Image: returns the argument,
Nothing: results in an empty transparent image.

Arguments:

args (Image|List<Object>|Number|Object|String, optional):

Constructor argument.

Returns: Image

ee.ImageCollection(args)

ImageCollections can be constructed from the following arguments:

A string: assumed to be the name of a collection,
A list of images, or anything that can be used to construct an image.
A single image.
A computed object - reinterpreted as a collection.

Arguments:

args (ComputedObject|Image|List<Object>|String):

The constructor arguments.

Returns: ImageCollection

这是两个之间的差异，然后再看reduce region的函数

reduceRegion(reducer, geometry, scale, crs, crsTransform, bestEffort, maxPixels, tileScale)

Apply a reducer to all the pixels in a specific region.

Either the reducer must have the same number of inputs as the input image has bands, or it must have a single input and will be repeated for each band.

Returns a dictionary of the reducer's outputs.

Arguments:

this:image (Image):

The image to reduce.

reducer (Reducer):

The reducer to apply.

geometry (Geometry, default: null):

The region over which to reduce data. Defaults to the footprint of the image's first band.

scale (Float, default: null):

A nominal scale in meters of the projection to work in.

crs (Projection, default: null):

The projection to work in. If unspecified, the projection of the image's first band is used. If specified in addition to scale, rescaled to the specified scale.

crsTransform (List, default: null):

The list of CRS transform values. This is a row-major ordering of the 3x2 transform matrix. This option is mutually exclusive with 'scale', and replaces any transform already set on the projection.

bestEffort (Boolean, default: false):

If the polygon would contain too many pixels at the given scale, compute and use a larger scale which would allow the operation to succeed.

maxPixels (Long, default: 10000000):

The maximum number of pixels to reduce.

tileScale (Float, default: 1):

A scaling factor between 0.1 and 16 used to adjust aggregation tile size; setting a larger tileScale (e.g. 2 or 4) uses smaller tiles and may enable computations that run out of memory with the default.