Mosaic tool

Author: Lara Ferrighi, laraf@met.no Author: Magnar Eivind Martinsen, magnarem@met.no

Drupal tool for displaying Sentinel products on an OpenLayers map.

Software metadata provided in the codemeta.json file.

Requirements and build

Mosaic requires Drupal 11.4+, the Vite contributed module, and the current metsis_drupal module. The latter provides the Solr connector/query factory and shared frontend WMS helpers. No ol-ext dependency is used.

Run the following from this module's root:

npm ci
npm run build

Commit the generated dist/ assets and manifest when deploying the module without a Node build step. Vite discovers METSIS in the sibling ../metsis_drupal directory or the local test site's web/modules/custom/metsis_drupal directory. For another layout, set METSIS_DRUPAL_PATH to the installed module directory before building.

For development, run npm run dev and clear Drupal's library cache. The local library configuration probes http://localhost:5173 and serves HMR through https://mosaic.ddev.site:5173; adjust the Vite library/server configuration for a different development hostname. Production uses the manifest when the development server is not running.

The shared Vite development-client library also needs the browser-facing URL in the test site's local settings, otherwise it defaults to the browser's http://localhost:5173:

$settings['vite']['devServerUrl'] = 'https://mosaic.ddev.site:5173';
$settings['vite']['devServerProbeUrl'] = 'http://localhost:5173';

For production, set $settings['vite']['useDevServer'] = FALSE.

The repository root is the module source. web/ is only the local Drupal test site. Its module directory must link new root files/directories as well as existing ones (including mosaic.services.yml and dist/). Do not edit test-site copies of module code.

Search and map behavior

Open /services/mosaic. All queries are scoped to collection:NBS, metadata_status:Active, a WMS URL, and Sentinel-1 or Sentinel-2. Only the selected region is queried. The initial time interval is the preceding 24 hours of temporal_extent_start_date, meaning satellite recording time, not ingestion time. Selecting a historical date shows that UTC day's recordings. Mission and satellite checkboxes refine the query; selecting no missions returns no products, while selecting no individual satellites means all satellites in the selected missions.

The acquisition-start field intentionally remains the time predicate: temporal_extent_period_dr intersection could include recordings starting before the selected interval and would change that agreed meaning.

Core HTMX updates the server-rendered filter/results fragment. The map stays mounted in the active theme's normal page layout; Mosaic does not override the theme's page template. English and Norwegian use Drupal translation rather than separate duplicated templates.

The map uses proj4's built-in EPSG:5041 definition and native OpenLayers WebGL tiles. Canvas tiles and a visible notice provide graceful degradation when WebGL is unavailable or its context is lost. WMS and basemap endpoints must support CORS; Mosaic does not proxy external requests.

METSIS WMS helpers preserve endpoint-specific parameters, discover selectable layers, and exclude NBS. Capabilities discovery has six concurrent workers; imagery appears progressively. A common layer selector appears only when every returned WMS resource resolves to the same nonempty selectable layer set. Capability failures and tile failures are reported explicitly.

The native keyboard/touch date slider controls the end of a 1-, 6-, or 24-hour acquisition window. The initial selection is the full 24 hours. The indeterminate activity bar tracks capability discovery and active WMS tile requests; it does not claim a percentage with an unknown request total.

Product/region bbox intersections limit WMS layer extents before tile selection, with sampled polar reprojection, no extra zoom-level preloading, and no horizontal wrapping. Previous region layers stop rendering before a switch; cached layers are retained up to 64 entries and parsed capabilities up to 128 entries. Changing time does not refresh sources. Boundary tiles can extend beyond the region, and already-started requests may still finish. Panning is not restricted. Up to 1500 newest matching products are returned; truncation and invalid map metadata are disclosed.

Checks

npm test
npm run build
vendor/bin/phpcs src tests/src mosaic.module
vendor/bin/phpunit -c web/core/phpunit.xml.dist tests/src/Unit

The PHP tests use the local Drupal test site's autoloader. Check the page in Olivero and Solo, including narrow layouts, HTMX filter updates, time scrubbing, real WMS requests, and Canvas fallback.