使用表格生成要素集
主要功能
使用在线数据筛选生成要素集
代码
// Create a FeatureCollection from a Fusion Table.
// Select "desert" features from the TNC Ecoregions fusion table.
var fc = ee.FeatureCollection('ft:1Ec8IWsP8asxN-ywSqgXWMuBaxI6pPaeh6hC64lA')
.filter(ee.Filter.stringContains('ECO_NAME', 'desert'));
// Paint into a blank image. Cast to byte() so we can use more than 1 color.
var image1 = ee.Image().byte().paint(fc, 'ECO_NUM');
// Display the image using random colors for each value.
Map.setCenter(-109.687, 30.524, 5);
Map.addLayer(image1.randomVisualizer());
步骤分析
- 使用在线数据，筛选字段属性
- 将筛选出的要素输出到一个数据对象中
- 设置地图中心，缩放等级
- 添加图层，展示结果
主要方法
- ee.FeatureCollection()
FeatureCollections can be constructed from the following arguments:
- A string: assumed to be the name of a collection.
- A single geometry.
- A single feature.
- A list of features.
- A computed object: reinterpreted as a collection.
Arguments:
args (ComputedObject|Feature|FeatureCollection|Geometry|List<Object>|Number|String):
The constructor arguments.
column (String, optional):
The name of the geometry column to use. Only useful with constructor type 1.
Returns: FeatureCollection
创建要素集。
- ee.Filter.stringContains()
Creates a unary or binary filter that passes if the left operand, a string, contains the right operand, also a string.
Arguments:
leftField (String, default: null):
A selector for the left operand. Should not be specified if leftValue is specified.
rightValue (Object, default: null):
The value of the right operand. Should not be specified if rightField is specified.
rightField (String, default: null):
A selector for the right operand. Should not be specified if rightValue is specified.
leftValue (Object, default: null):
The value of the left operand. Should not be specified if leftField is specified.
Returns: Filter
过滤器，判断是否包含特定字符串。
输入参数：左属性（字符串），右值，右属性（字符串），左值
- ee.Image.paint()
Paints the geometries of a collection onto an image.
Arguments:
this:image (Image):
The image on which the collection is painted.
featureCollection (FeatureCollection):
The collection painted onto the image.
color (Object, default: 0):
Either the name of a color property or a number.
width (Object, default: null):
Either the name of a line-width property or a number.
Returns: Image
将地理几何要素输出到为影像数据。
输入参数：影像（输出结果），要素集，颜色，宽度
- ee.Image.randomVisualizer()
Creates a vizualization image by assigning a random color to each unique value of the pixels of the first band. The first three bands of the output image will contan 8-bit R, G and B values, followed by all bands of the input image.
Arguments:
this:image (Image):
Image with at least one band.
Returns: Image
对影像数据的第一波段中的不同值赋予随机颜色输出彩色图像，输出结果为8位RGB影像
输入参数：影像对象（需至少包含一个波段）
