Zarr-Cesium Visualization Toolkit

CesiumJS providers for interactive 2D and 3D visualization of environmental geospatial data stored in Zarr.

• Documentation: https://noc-oi.github.io/zarr-cesium/docs
• Demo: https://noc-oi.github.io/zarr-cesium/

Overview

The Zarr-Cesium Visualization Toolkit provides CesiumJS data providers for rendering n-dimensional datasets stored in the Zarr format — streamed directly from cloud object stores (HTTP/S3/GCS) without preprocessing, conversion, or a backend server.

Features

• Zarr v2 and v3 compatibility Read datasets from any Zarr store, including public cloud object storage.

• Multiscale or single-scale datasets Automatically handles multi-resolution datasets (from ndpyramid) or standard Zarr datasets.

• 2D & 3D visualization Render gridded scalar, vector, and volumetric data directly in CesiumJS.

• CRS-aware Supports EPSG:4326 (Geographic) and EPSG:3857 (Web Mercator) coordinate systems with automatic detection and transformation.

• On-demand streaming Tiles and slices are fetched and decoded dynamically — no conversion to imagery tiles required.

• GPU-accelerated rendering Uses WebGL and Cesium primitives for fast visualization of large datasets.

• Style and animation controls Programmatic control of color maps, opacity, scale range, slice spacing, and vertical exaggeration.

Architecture

The toolkit provides three Cesium provider classes, each specialized for a different data type:

| Provider Class | Purpose | Description | | -------------------------- | -------------------- | ----------------------------------------------------------------------------------------- | | ZarrLayerProvider | 2D scalar fields | Renders single-level variables as Cesium imagery layers (e.g., temperature, chlorophyll). | | ZarrCubeProvider | 3D volumetric fields | Renders volumetric cubes with horizontal and vertical slices (e.g., ocean temperature). | | ZarrCubeVelocityProvider | 3D vector fields | Visualizes vector flow (u/v components) using animated particle advection. |

Installation

npm install zarr-cesium

Run the demo website locally

To run the demo website locally, clone the repository:

git clone https://github.com/noc-oi/zarr-cesium.git
cd zarr-cesium/demo

Create a .env file in the demo directory with your Cesium access token:

VITE_CESIUM_TOKEN=your_cesium_access_token_here

Install dependencies and start the development server:

npm install
npm run dev

The demo site will be available at http://localhost:3000.

If you want to use your own Zarr datasets, you can modify the demo code in demo/src/application/data/layers-json.tsx to point to your data URLs. You may need to adjust variable names, bounds, and other parameters accordingly.

Providers

1. ZarrLayerProvider

Renders 2D scalar fields as Cesium imagery overlays using WebGL. It supports both single-scale and multiscale Zarr datasets, and provides GPU-accelerated color mapping.

Example:

import { ZarrLayerProvider } from 'zarr-cesium';
import { Viewer } from 'cesium';

const viewer = new Viewer('cesiumContainer');

const options = {
  url: 'https://example.com/data.zarr',
  variable: 'salinity',
  colormap: 'viridis',
  scale: [30, 40]
};
const layer = await ZarrLayerProvider.createLayer(viewer, options);

viewer.imageryLayers.add(layer);

For more details, see the Zarr-Cesium documentation.

https://github.com/user-attachments/assets/33fc6dd2-38fa-4b20-a346-0a175f90eba1

Example of visualizing a Zarr dataset in a CesiumJS map using Zarr-Cesium. You can easily change the timestamp, colormap, and scale.

2. ZarrCubeProvider

Renders 3D volumetric Zarr cubes as Cesium primitives — including vertical and horizontal slices. It supports both Zarr v2/v3 and multiscale datasets, with adjustable color mapping and vertical exaggeration.

Example:

import { ZarrCubeProvider } from 'zarr-cesium';
import { Viewer } from 'cesium';

const viewer = new Viewer('cesiumContainer');

const cube = new ZarrCubeProvider(viewer, {
  url: 'https://example.com/ocean_temp.zarr',
  variable: 'temperature',
  bounds: { west: -20, south: 30, east: 10, north: 60 },
  colormap: 'plasma',
  verticalExaggeration: 50
});

await cube.load();

For more details, see the Zarr-Cesium documentation.

https://github.com/user-attachments/assets/8b066725-c6c7-4b7a-9fc0-d632b623937c

Example of visualizing a 4D Zarr dataset in a CesiumJS map as a 3D cube using Zarr-Cesium. You can easily change slices and view the cube in different ways, styles, and scales.

3. ZarrCubeVelocityProvider

Renders 3D velocity fields from U/V components as animated wind/current layers using cesium-wind-layer.

It supports both Zarr v2/v3 and multiscale datasets, with configurable slice spacing and particle animation parameters.

Example:

import { ZarrCubeVelocityProvider } from 'zarr-cesium';
import { Viewer } from 'cesium';

const viewer = new Viewer('cesiumContainer');

const velocity = new ZarrCubeVelocityProvider(viewer, {
  urls: {
    u: 'https://example.com/uo.zarr',
    v: 'https://example.com/vo.zarr'
  },
  variables: { u: 'uo', v: 'vo' },
  bounds: { west: -50, south: -20, east: 10, north: 20 },
  colormap: 'plasma'
});

await velocity.load();

For more details, see the Zarr-Cesium documentation.

https://github.com/user-attachments/assets/a54ddd70-9b00-4a3e-9cb9-41025cceffd0

Example of visualizing wind-speed vector data from Zarr in a CesiumJS map using Zarr-Cesium. This dataset is from Hurricane Florence, which occurred in 2018. You can easily change the timestamp, colormap, and particle speed.

DEVELOPMENT

For more details on how to contribute to the development of this toolkit, please refer to the DEV-README.md file.

Acknowledgements

This tool is built with:

• CesiumJS
• Zarrita
• cesium-wind-layer
• jscolormaps

This work is part of the Atlantis project, a UK initiative supporting long-term ocean observations and marine science in the Atlantic. The project is led by the National Oceanography Centre (NOC).