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How it works?

Lonboard is built on four foundational technologies:, GeoArrow, GeoParquet, and anywidget.

  • is a JavaScript geospatial data visualization library. Because uses the GPU in your computer to render data, it's capable of performantly rendering very large quantities of data.
  • GeoArrow is a memory format for efficiently representing geospatial vector data. As a memory format, GeoArrow is not compressed and can be used directly.
  • GeoParquet is a file format for efficiently encoding and decoding geospatial vector data. As a file format, GeoParquet contains very efficient compression, and needs to be parsed before it can be used. 1
  • anywidget is a framework for building custom Jupyter widgets that makes the process much easier than before.

How is it so fast?

Lonboard is so fast because it moves data from Python to JavaScript (in your browser) and then from JavaScript to your Graphics Processing Unit (GPU) more efficiently than ever before.

Other Python libraries for interactive maps exist (such as ipyleaflet), and even existing bindings to exist (such as pydeck). But those libraries encode data as GeoJSON to copy from Python to the browser. GeoJSON is extremely slow to read and write and results in a very large data file that has to be copied to the browser.

With lonboard, the entire pipeline is binary. In Python, GeoPandas to GeoArrow to GeoParquet avoids a text encoding like GeoJSON and results in a compressed binary buffer that can be efficiently copied to the browser. In JavaScript, GeoParquet to GeoArrow offers efficient decoding (in WebAssembly). Then is able to interpret the GeoArrow table directly without any parsing (thanks to @geoarrow/

GeoPandas is the primary interface for users to add data, allowing lonboard to internally manage the conversion to GeoArrow and its transport to the browser for rendering.

Lonboard's goal is to abstract the technical bits of representing and moving data so it can attain its dual goals of performance and ease of use for a vast audience.

  1. lonboard currently doesn't use "official" GeoParquet 1.0, because the 1.0 spec requires encoding geometries as Well-Known Binary (WKB) inside of the Parquet file. lonboard uses the highly-efficient GeoArrow encoding inside of GeoParquet (which may become part of the GeoParquet spec in 1.1). This is faster and easier to write when the writer and reader are both using GeoArrow anyways.