GEE学习笔记(26): 快速检测山东山火面积和明火位置

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目录:

  • 备注：以下纯属学习，数据真实性还有待检测

  • 看到这样的事情真的很痛惜，这么好的景色，几天之内就化为灰烬

1 数据说明

  • 数据来源：选用Sentinel-2的影像

  • 具体数据和结果如下所示

假彩色

2 结果

  1. 山火发生前后真彩色对比
发生前 发生后
发生前 发生后
  1. 明火检测和过火面积估测

| 发生前 | 发生后 |

| :---: | :---: |

| 发生前 | 发生后 |

3 详细代码

var roi =

/* color: #d63000 */

/* shown: false */

/* displayProperties: [

{

"type": "rectangle"

}

] */

ee.Geometry.Polygon(

[[[120.0459831156161, 35.9860397515576],

[120.0459831156161, 35.90905077800842],

[120.16854933876063, 35.90905077800842],

[120.16854933876063, 35.9860397515576]]], null, false);

Map.centerObject(roi, 12);

var addVariables = function(image){

var FDI = image.expression("SWIR2/Redge",{

Redge: image.select("B5"),

SWIR2: image.select("B12")

}).rename('FDI');

var ndvi = image.normalizedDifference(['B8','B4']).rename('NDVI')

return image.addBands([FDI,ndvi]);

}

var S2 = ee.ImageCollection('COPERNICUS/S2')

.filterBounds(roi)

.filterDate("2020-04-21", "2020-04-28")

.sort("system:time_start",false)

print(S2,"s2")

print("时间",S2.first().date().advance(8,"hour"))

var S2_01 = ee.ImageCollection('COPERNICUS/S2')

.filterBounds(roi)

.filterDate("2020-04-21", "2020-04-24")

.map(addVariables)

.mosaic()

.clip(roi)

var S2_02 = ee.ImageCollection('COPERNICUS/S2')

.filterBounds(roi)

.filterDate("2020-04-26", "2020-04-27")

.map(addVariables)

.mosaic()

.clip(roi)

// true image

var visParams01 = {"bands": ["B12", "B8", "B4"],"min": 500,"max": 4000, gamma: 1.5, scale: 10};

Map.addLayer(S2_01,visParams01, "S2_01_true");

Map.addLayer(S2_02,visParams01, "S2_02_ture");

// 检测火点

var FDI01 = S2_01.select("FDI");

var FDI02 = S2_02.select("FDI");

var fire_FDI = FDI02.subtract(FDI01);

var fire_FDI = FDI02.gte(3).and(fire_FDI.gte(2));

var fire_FDI = fire_FDI.updateMask(fire_FDI.eq(1)).rename('fire_FDI');

Map.addLayer(fire_FDI, {palette: 'red'}, 'FDI');

// 检测火点面接

var FDI_area = fire_FDI.multiply(ee.Image.pixelArea());

var FDI_area = FDI_area.reduceRegion({

reducer: ee.Reducer.sum(),

geometry: roi,

scale: 10,

maxPixels: 1e13

});

print("明火检测面积:",FDI_area);

// 统计燃烧的面积

var ndvi01 = S2_01.select("NDVI");

var ndvi02 = S2_02.select("NDVI");

var fire_area = ndvi01.subtract(ndvi02);

var fire_area = fire_area.gte(0.1)

.and(ndvi01.gte(0.15))

.and(ndvi02.lte(0.15));

var fire_area = fire_area.updateMask(fire_area.eq(1)).rename('fire_area');

Map.addLayer(fire_area,{min: 0, max:1, palette: ['green','red']}, "fire_area");

var fire_area = fire_area.multiply(ee.Image.pixelArea());

var fire_area = fire_area.reduceRegion({

reducer: ee.Reducer.sum(),

geometry: roi,

scale: 10,

maxPixels: 1e13

});

print("过火检测面积:",fire_area);