Streaming & Storage Settings

Two Settings-dialog panels control how elevation data gets from a COG into the renderer, and what the browser keeps between sessions. Neither affects what is computed — only how it's fetched, how precisely it's encoded, and whether it survives a reload.

Streaming Settings

COG Streaming: MapLibre vs Titiler

Two engines can turn a Cloud-Optimized GeoTIFF into map tiles:

• MapLibre (default) — @geomatico/maplibre-cog-protocol reads the COG directly in the browser via HTTP range requests: no middleware, faster, and no shared-server load. The COG must be reachable with CORS enabled and already in Web Mercator (see BYOD for the gdalwarp/gdal_translate fix-ups) — a CORS-blocked file is the usual reason to flip this switch.
• Titiler — a Titiler middleware instance fetches the remote COG server-side and streams standard TMS tiles back. More tolerant (it reprojects and proxies CORS-less files), at the cost of an extra hop and server load. Contour Lines always use this path — they can't read a local file or raw COG directly.

The Titiler Endpoint field at the bottom of the panel points both the streaming fallback and the export path at your own instance (default https://titiler.xyz); it travels with a Project export so a shared project keeps working against the same server.

High-Precision Elevation Quantization

Visible only on the MapLibre/COG-protocol path. Elevation tiles are quantized into an RGB packing — Mapbox Terrain-RGB steps at 10 cm, Terrarium at ~3.9 mm. This switch re-encodes streamed COGs as Terrarium instead of Terrain-RGB: slower streaming, but flat or gently-sloped surfaces stop banding in the derivative modes (slope, curvature, hillshade on near-flat terrain make 10 cm steps very visible). The terrain-analysis pipeline page covers why each visualization mode picks the packing it does.

DTM Export without Titiler

Client-side GeoTIFF export: the browser range-reads and mosaics tiles/COGs directly, bypassing Titiler's server-side size cap. Works for COG, Terrain-RGB, and Terrarium sources — including a local COG file that no server could reach.

Cache Computed Viz-Mode Tiles

Keeps finished computed tiles (Terrain Analysis, detectors, …) in an in-memory cache of up to ~96 MB, so toggling a mode off and back on redisplays instantly instead of recomputing every visible tile. Costs memory, saves recompute — turn it off on low-RAM machines.

Browser Local Storage Persistence

The app never uploads your local data anywhere; this panel controls what the browser itself remembers, backed by OPFS (private per-site storage):

• Local COG Files — copies files picked via the Local COG source type into OPFS so they don't need re-picking after a reload.
• Vector Layers (TerraDraw) — keeps drawn/imported Drawing layers across reloads.

Each category shows a live readout — file/layer count, bytes used, and the site's total browser storage quota — with a Clear button to free the space. Everything persisted here (plus bookmarks, custom sources, and settings) can also be bundled into a portable Project export .zip.

Separately from OPFS, plain localStorage holds the small stuff — API keys, custom color ramps, collapsed-section state, beta flags — as described in the architecture overview.