Layers & Symbology¶

The Layers panel (📑) is the central control surface for everything on the map canvas. Open it from the Tool Ribbon on the right edge.

Loading Layers¶

Supported Formats¶

Layer Types & Icons¶

Source Badges¶

Performance & Large Files¶

AI-Hydro is optimised to stay responsive when many or large layers are loaded simultaneously.

What happens under the hood¶

The "simplified" badge¶

If a loaded file contains more than 2 million coordinates (e.g., a high-density river network or continental-scale polygon set), the layer is automatically simplified before display:

• Coordinates are snapped to a grid sized to ~1/10 000 of the data extent (minimum 1 × 10⁻⁵°, roughly 1 m at the equator).
• Adjacent duplicate vertices are removed. Point features are never touched.
• A blue simplified badge appears in the layer row. Hover over it to see the original and reduced coordinate counts.

The simplified version is display-only — the source file on disk is not modified.

When does this matter? At typical screen resolutions, sub-metre coordinate differences are sub-pixel. Simplification has no visible effect on the map but can reduce a 5 M-coordinate watershed delineation to < 500 K, cutting GPU tessellation time by 10×.

Status Pills¶

Each layer row shows a coloured pill describing its analysis readiness:

A stale badge appears when the source file has changed since the layer was loaded. Click ⟳ to reload.

Profile charts and cursor readings require an analysis-ready raster. If the value probe shows nothing, open Symbology and click Load raster values.

Per-Layer Controls¶

Renaming¶

Double-click a layer name to rename it inline. The new name is saved to display_name metadata and reflected everywhere — including the live legend and Map Plate Composer.

Opacity¶

Each visible layer shows an opacity slider (0–100%) below the name row. Rasters blend against the basemap; vector layers multiply against stroke and fill alpha.

Global Controls¶

Layer Reordering¶

Drag a layer row using its ⠿ gripper, or use ↑/↓ buttons, to change render order. Layers lower in the list render on top. This controls which raster is sampled by transect profiles and the cursor value probe.

Point Clustering¶

For dense point networks (USGS gauges, precipitation stations), enable Cluster in the layer row. Points within the same grid cell at low zoom are aggregated into a single marker sized by count.

Symbology Editor¶

Click a layer's colour swatch or the 🎨 icon to open the inline editor.

Vector Layers¶

Raster Layers¶

The histogram is only shown for analysis-ready rasters. Switching colormaps instantly recolors the histogram bars to match.

Graduated (Choropleth) Symbology¶

For vector layers, click By Attribute to open the graduated symbology editor:

1. Select a numeric attribute from the layer's feature properties
2. Choose a classification method: Natural Breaks, Equal Interval, or Quantile
3. Pick a colour ramp: viridis, YlOrRd, Blues, RdYlGn, or custom stops
4. Set the number of classes (2–7)
5. Click Apply — breaks and colours are stored in layer metadata and re-applied on every render

The map legend updates automatically to show the colour ramp and class boundaries.

GeoTIFF Support¶

GeoTIFFs are decoded with geotiff.js entirely in-browser — no server round-trip.

Supported CRS¶

Warping uses bilinear interpolation; output is capped at 512 px on the long axis. Unsupported CRSs return a clear error — reproject to EPSG:4326 first using gdalwarp or QGIS.

Layers from Python Analysis Tools¶