Sankey Map

Overview

Sankey Map Sankey diagrams are a type of flow diagram where the width of the arrows are proportional to the volume being described. MapProvision now offers the ability to create Sankey Maps overlaid on top of a map to show data flows between geographic locations. This new visualization provides an easy way to understand data flows and volumes within a geographic context. The following example shows Fish Imports into Japan. The width of each path is proportional to the volume of imports between the two exporting countries.

Hovering the mouse over a given path will show a tool tip displaying the underlying metric displaying the size of the import from that country.

Hovering the mouse over a given start or end arrow at a node will show a tool tip displaying all the underlying metrics from or to that node. Doing this will also make all other node’s paths transparent so that the selected data is more prominent.

You can display multiple Sankey layers on the map at the same time and adjust the opacity of each layer on the fly. To do this you click the selected layer in the layer tree and use the opacity slider tool to drag the opacity up and down.

Symbolgy

• In the Viewer when viewing the layer where the symbology changes will stay in effect only until the layer tree is reloaded.
• In the Manager when adding or updating the dataset. These changes will stay in effect indefinitely until the symbology is again updated.

In the Viewer you can temporarily change the Sankey Map layer symbology in the Viewer by right clicking the layer in the layer tree and selecting symbology from the menu.

Or you can click the Symbology button while the layer is selected in the layer tree. Selection in the layer tree means the item in the tree has been clicked and is highlighted it does not mean that the item has its checkbox ticked.

In the Manager you can change the layer's symbology by editing it's symbology panel in the Symbology tab. These changes will stay in effect until the symbology is again updated

Color Bands

You can change the colors used to represent each path that is used to render the Sankey Map layer.

You can also select the color the path displays as ahen selected and the color of the source and target arrows, as well as the path thickness and opacity.

You can click the select button to popup a color picker (shown below) to help choose your desired color.

Uploading Sankey Map data sets

You will need to prepare your data file for upload. The Sankey data file format is different to the file format expected for other MapProvision layers as each data record requires a start and end point and the ability to craft custom descriptions for the tool tips when the user is interacting with the Sankey Maps.

The basic Sankey data format is a Comma Separated Values (.csv) file shown in the format below. There is a source place name and a target place name and a value for the Sankey Path.

You can download the file used in this example by clicking here.

To display more information in the Sankey Map there are optional extra columns to add detailed descriptions to the Sankey Map when the user hovers over a Sankey Path or Start/End Point arrow.

The following example shows an example Sankey data format is a Comma Separated Values (.csv) file with detailed descriptions and units of measure added.

You can download the file used in this example by clicking here.

The Sankey Map uploader has a large number of place names such as countries and cities that it can recognise and create the known coordinate for you automatically on the map. Often you will want to use your own coordinates instead of a place name so you can chart data to and from places that are more arbitrary and not recognised automatically by the uploader. To use your own coordinates to specify source and target Sankey locations the following field names are supported in your CSV file:

• source_lat
• source_lng
• target_lat
• target_lng

The following example shows an example Sankey data format is a Comma Separated Values (.csv) where a mix of plain English place names are used along with specific coordinates specified:

You can download the file used in this example by clicking here.

Further Info

For a full walk through showing how to easily create your own Sankey Maps this Blog Article takes you through the process.