Data Visualisation

1. Introduction

The EO DataHub integrates TiTiler, a dynamic tile server that makes it easy to visualise geospatial data. With TiTiler, you can adjust band combinations, apply colour maps, and generate map tiles on-the-fly, all without having to download entire datasets. This means you can quickly explore and preview geospatial data directly in your web browser, or bring it into third-party GIS tools like QGIS.

This guide covers:

How TiTiler fits into the EO DataHub.
Accessing both public and private datasets (where applicable).
Visualising data directly from STAC catalogues as WMTS services.
Configuring visualisation parameters before integrating them into your own workflow.
Adding EO DataHub tile services into QGIS or other GIS software.

Quick Links:

2. Understanding TiTiler in the EO DataHub

The EO DataHub offers multiple TiTiler endpoints configured for different data types:

Public “High-Priority” Datasets: Freely available collections that the EO DataHub team have chosen to highlight.
Private Workspace Data (Coming Soon): Your own data, accessible only to you through authenticated sessions.

Supported Data Formats:

GeoTIFF: Standard geospatial raster image format.
Cloud-Optimised GeoTIFF (COG): GeoTIFF optimised for cloud-based access and on-the-fly processing.
NetCDF: A format widely used for scientific data, often including multiple variables over space and time.
Zarr: A chunked, compressed, multidimensional array format often used for large datasets.
Kerchunk: A method for creating virtual datasets from cloud object storage without reading entire files.

Protocols & Services:

XYZ Tiles: A simple, widely supported web mapping format.
WMTS (Web Map Tile Service): A standardised way to serve tiled geospatial data, easily integrated into GIS software.

3. Browsing Data Through the EO DataHub UI

The easiest way to begin exploring what’s available is to use the EO DataHub’s Resource Catalogue:

Open the Catalogue:
Visit https://staging.eodatahub.org.uk/static-apps/stac-browser/main/index.html#//api/catalogue/stac/?.language=en
Browse Collections:
The catalogue contains a range of datasets, some fully public and others potentially restricted. Browse through collections to find one of interest.
Select a Collection and Item:
Each collection holds multiple items, such as satellite scenes or processed outputs. Click on a collection, then choose an item to see its assets.

Screenshot_23-12-2024_9285_test.eodatahub.org.uk

4. Open the Visualisation Form:
Most items have one or more assets. For formats like COG, NetCDF, Kerchunk, or Zarr, you’ll see a small map icon. Clicking it opens a form where you can customise how the data will appear when served via TiTiler.

Screenshot_23-12-2024_92834_test.eodatahub.org.uk

4. Configuring Your Visualisation

Once in the visualisation form, you can refine the appearance of your data:

Band/Variable Selection:
Pick which bands (for raster formats) or variables (for NetCDF/Kerchunk) you’d like to display.
Tile Matrix Set:
Choose a tile matrix set (spatial reference system) to define how tiles are generated.
Rescaling:
Enter numeric ranges (e.g., 0,100) to adjust contrast. Use the min/max or histogram tools to guide your choices:
- Min/Max Button: Quickly derive suitable ranges directly from your data.
- Histogram Button: View data distribution to set meaningful rescale values.
Colormap:
Apply a colour scheme from a dropdown list to highlight features or patterns in your data.

Screenshot_23-12-2024_93020_test.eodatahub.org.uk

Preview Your Settings:

Click the Preview button to open a new tab and see a live preview of your tile configuration. If it doesn’t look right, simply return to the form and adjust the parameters.

5. Integrating into GIS Software

After configuring your visualisation, you’ll find an XYZ Tile URL and possibly a WMTS GetCapabilities URL for your data.

XYZ Tiles:

Screenshot_23-12-2024_93346_test.eodatahub.org.uk

When copied, will have a URL similar to this:

https://staging.eodatahub.org.uk/titiler/core/cog/tiles/WebMercatorQuad/{z}/{x}/{y}?url=YOUR_DATA_URL&bidx=1&rescale=0%2C100&colormap_name=viridis

You can add XYZ tiles directly to QGIS or any other GIS application that supports them. You can add this into QGIS through Layer > Add Layer > Add XYZ Layer and pasting in your generated URL.

WMTS GetCapabilities URL:

For some data, you’ll also have a WMTS endpoint. For example:

https://staging.eodatahub.org.uk/titiler/core/cog/WebMercatorQuad/WMTSCapabilities.xml?tile_format=png&tile_scale=1&use_epsg=false&url=YOUR_COG_URL&bidx=1&rescale=0%2C255

You can add this WMTS endpoint into QGIS by going to Layer > Add Layer > Add WMTS Layer and pasting in the GetCapabilities URL.

rsz_1screenshot_from_2024-12-23_09-43-10

6. Accessing Mosaiced WMTS for High-Priority Public Datasets

For selected public datasets, the EO DataHub team has agreed to offer a fully mosaiced WMTS view. These datasets are enhanced with a special renders configuration in their STAC metadata, instructing TiTiler-STAC to serve them as a single seamless mosaic rather than as individual scenes. This makes it much easier to integrate large, multi-scene collections into your GIS workflows right away.

Technical explanation of how our WMTS is configured:

Within a STAC collection’s JSON, a renders section defines how to combine certain assets, which bands or variables to use, how to rescale values, and the spatial reference and zoom levels to support. For example:

{
    "renders": {
        "rgb": {
            "title": "RGB",
            "assets": ["cog"],
            "bidx": [1, 2, 3],
            "rescale": [
                [0,100],
                [0,100],
                [0,100]
            ],
            "resampling": "nearest",
            "tilematrixsets": {
                "WebMercatorQuad": [0, 30]
            }
        }
    }
}

How to Access the Mosaiced WMTS:
To view the mosaiced dataset as a WMTS service, take the relevant STAC catalog URL and append /wmts, along with the necessary WMTS parameters. Different high-priority public datasets may be located in different catalogues, but the process remains the same - just adjust the <CATALOG_PATH> accordingly.

For example:

https://<EO_DATAHUB_STAC_URL>/<CATALOG_PATH>/wmts?<WMTS_PARAMS>

Which can become:

https://staging.eodatahub.org.uk/api/catalogue/stac/catalogs/supported-datasets/ceda-stac-catalogue/wmts?request=GetCapabilities&service=WMTS

Where:

EO_DATAHUB_STAC_URL: staging.eodatahub.org.uk/api/catalogue/stac/
CATALOG_PATH: e.g. catalogs/supported-datasets/ceda-stac-catalogue
WMTS_PARAMS: request=GetCapabilities&service=WMTS

This returns a WMTS GetCapabilities document that you can add directly into your GIS software. As the EO DataHub evolves, we will publish a reference list of which catalogues and datasets support these pre-configured mosaics.

In the example above, we have selected to view the sentinel2_ard layer over the day of 2023-02-13.