Google earth engine（GEE）——根据点绘制折线图

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发布于 2024-02-01 20:01:11

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代码可运行

文章被收录于专栏：GEE数据专栏，GEE学习专栏，GEE错误集等专栏

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代码可运行

因为这次要用到点的数据，所以首先看要用到的工具：

一座山从底下到山顶的一个爬坡变化情况

ui.Chart.image.byRegion(image, regions, reducer, scale, xProperty)

Generates a Chart from an image. Extracts and plots band values in one or more regions in the image, with each band in a separate series.

- X-axis = Region labeled by xProperty (default: 'system:index')

- Y-axis = Reducer output.

- Series = Band name.//这里明确给出了用byRegion就是返回一个序列

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. Defaults to ee.Reducer.mean().

scale (Number, optional):

Scale to use with the reducer in meters.

xProperty (String, optional):

Property to be used as the label for each Region on the x-axis. Defaults to 'system:index'.

Returns: ui.Chart

var elevation = ee.Image('CGIAR/SRTM90_V4');
//这个就是你要测量的点的位置信息并且可以命名名字
var waypoints = [
  ee.Feature(
      ee.Geometry.Point([-121.7353, 46.78622]),
      {'name': 'Paradise Ranger Station'}),
  ee.Feature(
      ee.Geometry.Point([-121.72529, 46.8093]), {'name': 'Pebble Creek'}),
  ee.Feature(
      ee.Geometry.Point([-121.72585, 46.8102899]),
      {'name': 'Start of Glacier'}),
  ee.Feature(
      ee.Geometry.Point([-121.7252699, 46.81202]), {'name': 'Glacier Point 1'}),
  ee.Feature(
      ee.Geometry.Point([-121.72453, 46.81661]), {'name': 'Glacier Point 2'}),
  ee.Feature(
      ee.Geometry.Point([-121.72508, 46.82262]), {'name': 'Little Africa'}),
  ee.Feature(
      ee.Geometry.Point([-121.7278699, 46.82648]), {'name': 'Moon Rocks'}),
  ee.Feature(ee.Geometry.Point([-121.73281, 46.8354]), {'name': 'Camp Muir'}),
  ee.Feature(ee.Geometry.Point([-121.75976, 46.85257]), {'name': 'Summit'})
];

//把这些点的集合弄成一个矢量集合，就是点要素
var rainierWaypoints = ee.FeatureCollection(waypoints);
//绘图用通过地图元素的形式进行绘制
var chart = ui.Chart.image.byRegion({
  image: elevation,
  regions: rainierWaypoints,
//设置你要统计分辨率，越小越精确
  scale: 200,
  xProperty: 'name'
});
chart.setOptions({
  title: 'Mt. Rainier Summit Trail Elevation',
  width:1000,
  height:500,
  vAxis: {
    title: 'Elevation (meters)'
  },
//图例的设置
  legend: 'none',
  lineWidth: 1,
  pointSize: 4
});

print(chart);

Map.addLayer(elevation, {min: 500, max: 4500});
Map.addLayer(rainierWaypoints, {color: 'FF0000'});
Map.setCenter(-121.75976, 46.85257, 11);

这是修改参数后的图形，设置了图形的长宽看起来更加合理