What are some tips to reduce the size and loading time of your GeoJSON data?

1 Simplify geometries

One way to reduce the size of your GeoJSON data is to simplify the geometries of your features, especially if they have many vertices or curves. Simplifying geometries means removing unnecessary points or smoothing out the shapes, while preserving the essential characteristics of the features. You can use tools like Mapshaper or Turf.js to simplify your GeoJSON data, either online or programmatically. Simplifying geometries can also improve the rendering speed of your web map, as it reduces the number of calculations and graphics needed.

2 Use projections

Another way to reduce the size of your GeoJSON data is to use projections that are more suitable for your geographic area and scale. Projections are mathematical transformations that convert the coordinates of your features from the spherical earth to a flat map. Different projections have different advantages and disadvantages, such as preserving shape, area, distance, or direction. By using a projection that matches your map's purpose and extent, you can reduce the number of digits in your coordinates, which can save space and improve accuracy. You can use tools like Proj4js or GeoJSON-Project to apply projections to your GeoJSON data.

3 Compress files

A third way to reduce the size of your GeoJSON data is to compress the files before sending them to the browser. Compressing files means reducing the amount of data by using algorithms that encode the information more efficiently. There are different types of compression methods, such as gzip, brotli, or zstd, that can be applied by your web server or by using tools like GeoJSON-Gzip or GeoJSON-Zstandard. Compressing files can significantly reduce the bandwidth and loading time of your web map, as it reduces the amount of data that needs to be transferred and decoded.

4 Apply filters

A fourth way to reduce the size of your GeoJSON data is to apply filters that remove or modify the features or properties that are not relevant or necessary for your web map. Filters are logical expressions that evaluate the attributes or geometries of your features and return a subset or a modified version of your data. You can use tools like OGR or GeoJSON-Filter to apply filters to your GeoJSON data, either on the server side or on the client side. Applying filters can help you tailor your data to your map's needs and preferences, as it reduces the amount of data that needs to be stored and displayed.