GEE绘制经纬网

绘制经纬网

主要功能

在每一度的经纬网区域内，绘制60条平均线

代码

// Draws 60 lat/long lines per degree using the pixelLonLat() function.

// Create an image in which the value of each pixel is its
// coordinates in minutes.
var img = ee.Image.pixelLonLat().multiply(60.0);

// Get the decimal part and check if it's less than a small delta.
img = img.subtract(img.floor()).lt(0.05);

// The pixels less than the delta are the grid, in both directions.
var grid = img.select('latitude').or(img.select('longitude'));

// Draw the grid.
Map.setCenter(-122.09228, 37.42330, 12);
Map.addLayer(grid.updateMask(grid), {palette: '008000'}, 'Graticule');

步骤分析

1. 生成两波段经纬度信息影像对象
2. 对经纬度进行取整，筛选阈值以下部分
3. 选择经纬网部分
4. 设置地图中心，缩放等级
5. 添加图层，只显示经纬网部分

主要方法

1. ee.Image.pixelLonLat()
   Creates an image with two bands named 'longitude' and 'latitude', containing the longitude and latitude at each pixel, in degrees.
   No arguments.
   Returns: Image

生成一个两波段影像，分别为经纬度，包含每一个像元的经纬度信息（度形式）

2. ee.Image.floor()
   Computes the largest integer less than or equal to the input.
   Arguments:
   this:value (Image):
   The image to which the operation is applied.
   Returns: Image

求输入影像范围内最大整数，取整功能