GEE 图表——sentinel-2和Landsat-8 影像各波段的图表展示和对比

简介

GEE 图表——sentinel-2和Landsat-8 影像各波段的图表展示和对比

函数

ui.Chart.image.regions(image, regions, reducer, scale, seriesProperty, xLabels)

Generates a Chart from an image. Extracts and plots the value of each band in one or more regions.

从图像中生成图表。提取并绘制一个或多个区域中每个波段的值。

• X-axis = Band labeled by xProperty (default: band name).
• Y-axis = Reducer output.
• Series = Region labeled by seriesProperty (default: 'system:index').

Returns a chart.

Arguments:

image (Image):

Image to extract band values from.

regions (Feature|FeatureCollection|Geometry|List<Feature>|List<Geometry>, optional):

Regions to reduce. Defaults to the image's footprint.

reducer (Reducer, optional):

Reducer that generates the value(s) for the y-axis. Must return a single value per band.

scale (Number, optional):

The pixel scale in meters.

seriesProperty (String, optional):

Property to be used as the label for each region in the legend. Defaults to 'system:index'.

xLabels (List<Object>, optional):

A list of labels used for bands on the x-axis. Must have the same number of elements as the image bands. If omitted, bands will be labeled with their names. If the labels are numeric (e.g. wavelengths), x-axis will be continuous.

Returns: ui.Chart

setChartType(chartType)

Sets the chartType of this chart.

Returns this chart.

Arguments:

this:ui.chart (ui.Chart):

The ui.Chart instance.

chartType (String):

The chart type; e.g 'ScatterChart', 'LineChart', and 'ColumnChart'. For the complete list of charts, see: https://developers.google.com/chart/interactive/docs/gallery

Returns: ui.Chart

setOptions(options)

Sets options used to style this chart.

Returns this chart.

Arguments:

this:ui.chart (ui.Chart):

The ui.Chart instance.

options (Object):

An object defining chart style options such as:

title (string) The title of the chart.

colors (Array) An array of colors used to draw the chart.

Its format should follow the Google Visualization API's options: https://developers.google.com/chart/interactive/docs/customizing_charts

Returns: ui.Chart

代码

/**
 * 利用哨兵-2 展示光谱特征
 * 使用哨兵-2 QA 波段屏蔽云层的功能
 * 参数 {ee.Image} 图像 圣天诺-2 图像
 * 返回 {ee.Image} 云遮蔽的哨兵-2 图像
 */

var water = /* color: #0b0dd6 */ee.Geometry.Point([-105.14670897556627, 40.52974114741079]),
    vegetation = /* color: #5f9f00 */ee.Geometry.Point([-105.1499286288265, 40.56408842507554]),
    builtUp = /* color: #660404 */ee.Geometry.Point([-105.0799766177181, 40.571912420808935]);

var dateStart = '2020-05-01'
var dateEnd = '2020-06-01'
Map.setCenter(-105.0381, 40.5538, 12); //centers on Fort Collins, CO
 
function maskS2clouds(image) {
  var qa = image.select('QA60');

  // Bits 10 and 11 are clouds and cirrus, respectively.
  var cloudBitMask = 1 << 10;
  var cirrusBitMask = 1 << 11;

  // Both flags should be set to zero, indicating clear conditions.
  var mask = qa.bitwiseAnd(cloudBitMask).eq(0)
      .and(qa.bitwiseAnd(cirrusBitMask).eq(0));

  return image.updateMask(mask).divide(10000);
}

var s2 = ee.ImageCollection('COPERNICUS/S2_SR')
                  .filterDate(dateStart, dateEnd)
                  // Pre-filter to get less cloudy granules.
                  .filter(ee.Filter.lt('CLOUDY_PIXEL_PERCENTAGE',20))
                  .map(maskS2clouds);

var visualization = {
  min: 0.0,
  max: 0.3,
  bands: ['B4', 'B3', 'B2'],
};

var COLOR = {
  WATER: '0b0dd6',
  VEG: '5f9f00',
  BUILT: '660404'
};

// 绘制光谱特征图
// 三个已知位置。
var fWater = ee.Feature(
    water, {'label': 'water'});
var fVegetation = ee.Feature(
    vegetation, {'label': 'veg.'});
var fBuiltUp = ee.Feature(
    builtUp, {'label': 'built-up'});

var LCpoints = ee.FeatureCollection([fWater, fVegetation, fBuiltUp]);
var s2ic = s2.filterBounds(LCpoints)
var s2image = s2ic.mean()

var s2image = s2image.select(['B2','B3','B4','B5','B6','B7','B8'])
var bandChart = ui.Chart.image.regions({
  image: s2image,
  regions: LCpoints,
  scale: 10,
  seriesProperty: 'label'
});
bandChart.setChartType('LineChart');
bandChart.setOptions({
  title: 'Sentinel-2 TOA band values near Fort Collins, CO',
  hAxis: {
    title: 'Band'
  },
  vAxis: {
    title: 'Reflectance'
  },
  lineWidth: 2,
  pointSize: 6,
  series: {
    0: {color: COLOR.WATER},
    1: {color: COLOR.VEG},
    2: {color: COLOR.BUILT}
  }
});

var wavelengths = [.458, .543, .650, .698, .733, .773, .785];

var spectraChart = ui.Chart.image.regions({
  image: s2image,
  regions: LCpoints,
  scale: 30,
  seriesProperty: 'label',
  xLabels: wavelengths
});
spectraChart.setChartType('LineChart');
spectraChart.setOptions({
  title: 'Landsat 8 TOA spectra near Fort Collins, CO',
  hAxis: {
    title: 'Wavelength (micrometers)'
  },
  vAxis: {
    title: 'Reflectance'
  },
  lineWidth: 2,
  pointSize: 6,
  series: {
    0: {color: COLOR.WATER},
    1: {color: COLOR.VEG},
    2: {color: COLOR.BUILT}  }
});

Map.addLayer(s2image)
print(bandChart);
print(spectraChart);

结果