Google earth engine（GEE）——LANDSAT8统计不同点的DN值
这次使用到的工具：
ui.Chart.image.regions(image, regions, reducer, scale, seriesProperty, xLabels)
和上次的.byregions不同下面黄色部分
Generates a Chart from an image. Extracts and plots the value of each band in one or more regions.
- X-axis = Band labeled by xProperty (default: band name).
- Y-axis = Reducer output.
- Series = Region labeled by seriesProperty (default: 'system:index').
系列 = 由 seriesProperty 标记的区域（默认值：'system:index'）属性值不同，主要是标记的点来进行属性添加的。
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):筛选器产生一个单个波段的值作为Y轴的值
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):
用作图例中每个区域标签的属性。默认为“系统：索引”
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
看代码：
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var landsat8Toa = ee.ImageCollection('LANDSAT/LC08/C01/T1_TOA');
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//设定一个变量三个颜色，一会分别作为三个点显示的颜色
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var COLOR = {
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PARK: 'ff0000',
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FARM: '0000ff',
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URBAN: '00ff00'
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};
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// 设置三个你想知道的点，并且把label作为其中的legend图例 Three known locations.
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var park = ee.Feature(
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ee.Geometry.Point(-99.25260, 19.32235), {'label': 'park'});
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var farm = ee.Feature(
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ee.Geometry.Point(-99.08992, 19.27868), {'label': 'farm'});
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var urban = ee.Feature(
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ee.Geometry.Point(-99.21135, 19.31860), {'label': 'urban'});
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//设置点的集合作为矢量点图层
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var mexicoPoints = ee.FeatureCollection([park, farm, urban]);
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landsat8Toa = landsat8Toa.filterBounds(mexicoPoints);
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//选取第一幅影像
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var mexicoImage = ee.Image(landsat8Toa.first());
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// 选取波段可以这么选省下一个个写，Select bands B1 to B7.
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mexicoImage = mexicoImage.select(['B[1-7]']);
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//这个就是根据你的矢量无论是点还是面还是线，一般都是通过region来进行图形的显示
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var bandChart = ui.Chart.image.regions({
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image: mexicoImage,
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regions: mexicoPoints,
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scale: 30,
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seriesProperty: 'label'
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});
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//设置你的图像显示，本次选择是线性图
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bandChart.setChartType('LineChart');
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//设置你的图上的属性，设置横纵轴和标题，线宽和点的大小
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bandChart.setOptions({
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title: 'Landsat 8 TOA band values at three points near Mexico City',
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hAxis: {
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title: 'Band'
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},
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vAxis: {
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title: 'Reflectance'
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},
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lineWidth: 1,
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pointSize: 4,
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series: {
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0: {color: COLOR.PARK},
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1: {color: COLOR.FARM},
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2: {color: COLOR.URBAN}
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}
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});
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// From: https://landsat.usgs.gov/what-are-best-spectral-bands-use-my-study最佳光谱值通过官网提供的，自己可以查询
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var wavelengths = [.44, .48, .56, .65, .86, 1.61, 2.2];
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//这个是光谱的值图像显示seriesProperty就是你的图例，label对应的键值
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var spectraChart = ui.Chart.image.regions({
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image: mexicoImage,
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regions: mexicoPoints,
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scale: 30,
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seriesProperty: 'label',
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xLabels: wavelengths
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});
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spectraChart.setChartType('LineChart');
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spectraChart.setOptions({
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title: 'Landsat 8 TOA spectra at three points near Mexico City',
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hAxis: {
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title: 'Wavelength (micrometers)'//（）中代表你的单位
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},
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vAxis: {
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title: 'Reflectance'
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},
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lineWidth: 1,
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pointSize: 4,
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series: {
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0: {color: COLOR.PARK},
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1: {color: COLOR.FARM},
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2: {color: COLOR.URBAN}
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}
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});
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//最后打印两个图表
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print(bandChart);
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print(spectraChart);
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Map.addLayer(park, {color: COLOR.PARK});
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Map.addLayer(farm, {color: COLOR.FARM});
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Map.addLayer(urban, {color: COLOR.URBAN});
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Map.setCenter(-99.25260, 19.32235, 11);
三个点的信息分别代表市区、城中心和农场
文章来源: blog.csdn.net，作者：此星光明2021年博客之星云计算Top3，版权归原作者所有，如需转载，请联系作者。
原文链接：blog.csdn.net/qq_31988139/article/details/118971766
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