# Multilayer Charts

You can superimpose multiple Pointmap, Linemap, Choropleth, and Geo Heatmap charts on one another to look for correlations between datasets.

To create a multilayer chart:

1. Create one of the charts that support multilayer.
2. Click the **Add Layer** tab.
3. Create another multilayer-compatible chart in the new layer.
4. Click the **Master** tab.
5. Adjust the **Opacity** and the **Zoom level** of the chart layers using the sliders on the right.

You can change the order of the layers by dragging the contents of a layer field on top of another layer field.

A single chart can have up to eight layers, depending on your server memory and processing capacity.

## Example: Opacity with Multilayer Charts

Create a new Pointmap. For the **Data Source**, use the official database of [UFO sightings](https://github.com/planetsig/ufo-reports/tree/master/csv-data).

Set the **Lon** measure to longitude and **Lat** measure to latitude. Set the **Size** measure to duration\_seconds. Set the **Color** measure to shape.

![](https://files.buildwithfern.com/heavyai.docs.buildwithfern.com/heavyai/49958a7d5635891ce08cb9e4ba811a887556d9556b04a51b867775a88ba093fb/docs/assets/SS_50-1.jpg)

Click the **Add Layer** tab, and create a Geo Heatmap. Set the data source to the flights\_2008\_7M database. Set **Lon** to dest\_lon and **Lat** to dest\_lat. Set the **Color** measure to AVG depdelay.

![](https://files.buildwithfern.com/heavyai.docs.buildwithfern.com/heavyai/bea7c8b521734c1b783bddd5183b1af0075e9d8829b76a066488b4124c9acdb9/docs/assets/SS_51.jpg)

The resulting chart compares a Geo Heatmap of flight departure delays to a Pointmap of UFO sightings.

Click the **Master** tab, and reduce the opacity of the UFOs Sighted chart to enhance the visibility of the flights\_2008\_7M delay information.

![](https://files.buildwithfern.com/heavyai.docs.buildwithfern.com/heavyai/b9d0fee8602d9abb0e7380cb019d050f43168fc75b8e117c24bd52cff00619c0/docs/assets/SS_52.jpg)

Clearly, some flights have been delayed where UFOs have been sighted, making it impossible to make a definitive statement that there is no correlation between the two datasets. Spooky.

## Example: Zoom Level with Multilayer Charts

You can configure the visibility of a layer based on zoom level.

This chart has two layers: a Pointmap based on tweets and a Choropleth based on 14 states defined by name, with the rest defined as Other. Currently, the chart is zoomed to level 5.

![](https://files.buildwithfern.com/heavyai.docs.buildwithfern.com/heavyai/844a4c4bec3fc9e606c42f8885e54684a1abd05fbdb2cf8cc41e56afbc92faa2/docs/assets/SS_53.jpg)

You determine that when you zoom to level 2, you no longer want to see the states layer, so you adjust the sliders to reflect this.

![](https://files.buildwithfern.com/heavyai.docs.buildwithfern.com/heavyai/21f39cdaa60be2a4cb579223b39ef3316657214c80863e8565b123d87328f1eb/docs/assets/SS_54.jpg)