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OpenLayers EZ Maps

Quickly develop basic and / or thematic OpenLayers web maps without coding by filling out a JSON config file!

TODO

  • Add classifications to choropleth
    • Natural Breaks
    • Equal Intervals
    • Quantiles
    • Standard Deviation
  • Add more breaks for choropleth classifications
    • 2 to 10
  • Button inside map container that updates styling
  • Refactor code
  • Update documentation

Features of the Application

  • Map Container
    • A view over some geography
    • View vector data (points, and / or polygons)
    • Base maps
    • OpenLayer Controls
      • Layer switcher to hide / show layers and base maps
      • Zoom in / out
      • Map scale
      • Full screen mode
      • Popup to show information of the clicked point marker
      • Legend

Getting Started

Project Development

  1. Clone the repo to your desired file directory
  2. Download Web Server for Chrome or Live Server in VSCode
  3. Open the web app in your preferred text editor if using Web Server for Chrome, otherwise use VSCode
  4. Use Chrome DevTools for debugging
    • Ensure that cache is disabled in DevTools
  5. Ensure the languages you work with are included in the system PATH

Feeding the Application Information

The JSON

JSON files are a way to transmit information to a web application. For the sake of this web application, the JSON file is used to send information locally so that the map container can be filled as desired. Users open up the JSON and enter in the details required for their visualization. You can see in the image below what an empty application.json file looks like. Examples are provided if you want to get started quickly.

Empty JSON

View

The view is where you want the map to be centred. The coordinates for the view are in the form of longitude and latitude.

Layers

Each layer you wish to add to the map container will have to be stored in the layers object. The layer object should be renamed to whatever you plan on titling the layer as.

Each layer also has attributes that may need to be filled. The id is for the code to identify your layer in the code whereas the title is more for the layer switcher, and popups.

Next, the shapeType is dependent on the GeoJSON vector data. The data can be point or polygon (see Types of GIS Data Explored: Vector and Raster). You have to write this in yourself so that the feature layer can be styled appropriately. To load the GeoJSON file into the map container, you'll need the url (or file path). For example, the url could be something like ./data/someFile.geojson.

Layer Styling

The style object is the important part of your visualization. The styleType can be custom or default. If you set the the styleType to default then the program will set the feature layer to the default theme based on the shapeType. If the styleType is set to custom then you can either select a single rgba color yourself or create a thematic (theme) feature layer.

The opacity can be any number you want in the range of 0 to 1 and must be set for any styleType whether default or custom.

The strokeColor will also depend on your styleType. If you didn't use the default then you have to choose an rgba color for the strokeColor yourself.

The scale and icon attributes depend on your shapeType. You should only fill these two out if your feature layer is of the type point. The scale value will be dependent on the size of the png itself, so if a scale of 0.05 shows the png as too large then you may need to update the GetProportionFn() in scales.js as the function is only currently designed for the Point Marker png we're using. The icon attribute should be set to the url or filepath of the icon you wish to use.

The theme attribute is likely the most complex of all the attributes. If you would like to do proportional symbol mapping, then you must fill in attributes for the size object. Ensure that only point data is used for this kind of thematic mapping. The proportional value should be whichever feature layer attribute column you're targeting in the GeoJSON file for the thematic mapping. For example, if you want to do proportional mapping by population size, your GeoJSON file might have a column title called pop_2020 that you want to target. Next, if you wanted to do some form of color mapping, such as choropleth, you'd want to fil in some of the attributes in the color object. You can only color two ways here, either choropleth or identified. Similar to proportional, you want to target either one of these themes using the attribute column title of interest. If you were to thematically identify each type of family hospital in a region, you could target something like ID for the identified attribute. If you want to thematically map something per capita you would use choropleth and look to target something like num_dentists_by_pop in your GeoJSON and then set a ranking. The ranking value is either quartile, quintile, or decile. Obviously, this depends on your preference. The scheme value should be whichever color scheme you'd like for this thematic visualization. The resources at the bottom of the README have good examples of color schemes for web mapping. Lastly, the legend attribute is what you might want to label the theme as in the legend.

Note: You can have a proportional symbol map that is also a choropleth or identified map. All depends on whether you want 1 or 2 themes for your feature layer. Just remember you can't have 3 themes set at the same time in one layer.

Layer Visibility

To show the feature layer in the map container, visible should be set to true. Otherwise, use false. Don't forget that if you're adding multiple layers, polygon feature layers should be visible before point feature layer layers.

Layer Popups

In the popup object you have two things to take note of. The unformatted array should contain titles of any attribute columns that interest you to show in the popup from the GeoJSON file and the formatted array are for those titles to be written in plain english since GeoJSON attribute column titles generally aren't pretty.

Polygon Layer Styling

Default

Custom

Point Layer Styling

Default

Custom

File Conversions and Data Handling

Setup
  1. Install Anaconda Navigator
  2. Get GeoPandas
    • Open Anaconda Prompt as admin and create a new environment called geo_env.
  3. Next, open Anaconda Navigator and click on Home and set Applications on to geo_env instead of base (root).
    • Click the install button for Spyder in the Anaconda Navigator.
  4. After all these steps you should be ready to run the new environment in Spyder for Python scripting.
    • Additionally, run the following command in the Spyder terminal: pip install openpyxl
Scripts

In the scripts folder you'll find Python files for converting SHP to GeoJSON, and Excel to GeoJSON. You'll also find scripts for cleaning up values in a GeoJSON and for adding new data to a GeoJSON.

Credit and Acknowledgements

Omar Kawach - Consultant

Bruno St-Aubin at Statistics Canada - Components

OpenLayers - Source Code

Jean-Marc Viglino - OpenLayers Extension

Matt Walker - OpenLayers LayerSwitcher

White Google Maps Pin

Innovation Support Unit - Department of Family Practice at UBC

Resources

Styling

D3 Color Schemes

ColorBrewer Cartography Color Advice

GIS

Spatial References

OpenLayers

OpenLayers Documentation