Tutorial - Contour Map
First, let's create our map and add a base map and a feature layer.
Then load some data. The data is grid data describing geospatial point elevation, a record of z value -9999 means there is no land data. Since the data is relatively big, intead of adding inline data, we load asynchronously, and use promise chain to chain up the following steps.
Once the data is loaded, we create the contour feature with default color range.
min: 0 means only showing data with elevation.
We could use a non-linear scale.
Or, we could use an custom color range.
We can use smooth contours instead of stepped contours.