3d_terrain — a 3-D terrain viewer for Kartverket's 1 m model

Updated 2026-10-26.

A web page that draws a 1 m terrain model (DTM) of any place in Norway in 3-D, with the sun and its shadows for any date and time, and two Python scripts that package a place — its terrain, a draped map, cliff areas and your own points — as a folder the page reads or as one self-contained HTML file that opens offline.

Live viewer: https://pcmoan70.github.io/3d_terrain/ — it opens on a flat map of Norway: tap a place, set the radius, Build 3-D view (a ? on the bar explains the controls). The model is chosen under Map in the panel and remembered on the device: a 1 m centre of ≤ 5 km inside a 10 m surround of ≤ 15 km to begin with (the 1 m detail is the whole view up to a 5 km radius), or 1 m alone (radius ≤ 5 km), or 10 m alone (radius ≤ 15 km). A 1 m square dragged past the 1 m limit (5 km radius) flips to the mixed model by itself — the inner frame (1 m, at that limit) appears inside the outer (10 m), each labelled at its corner; the same happens to a ?r= beyond 5 km at 1 m. The terrain is fetched straight from Kartverket's model (the Geonorge WCS) and shown, every slow step (fetching, reading the tiles, filling missing ground, the map, the sun) with a progress bar; ?lat=&lon=&r=&res= opens the same view by link, and Share… makes that link. The link may carry points to draw: #pts=<URL-encoded JSON>, an array of [lat, lon, name, text, colour] (text and colour optional, colour any CSS colour) — they become the overlay file Points from the link under Map, a pin each, name and text in the popup on a tap; this is how BirdsWhere's 3-D terrain button sends the dots on its map along. A map-built view grows from a tap: the popup on the terrain offers the model (1 m, 10 m, 1 m centre + 10 m around; preset to the Map choice) and, on one line under it, three buttons — Fetch+ fetches the tiles round the tapped point (those already in hand are not fetched again) and shows everything fetched so far as one view, the bounding square of the union of all the squares asked for (its centre and radius follow; ground no square covers is the grey "missing DTM" fill; the radius stops at 15 km, or 5 km with 1 m tiles only); Fetch moves the view to that square alone, at the chosen model, reusing the tiles in hand. At 1 m centre + 10 m around, the 1 m centre round the tapped point is the view's own 1 m radius if it was built with one, else the 1 m model's full reach (5 km) — fetched at 1 m even where 10 m tiles already cover it. 1 m and 10 m tiles together draw as one 1 m square about the centre (≤ 5 km, reaching the 1 m squares) in a 10 m surround — 1 m ground farther out shows at the coarse grid. Save then writes the whole view (every tile shown). Each 1 m tile is 4 MB in the browser's memory, so a dozen 1 m fetches is a few hundred MB. The demo folder is Preikestolen.

Everything happens in the browser: the page reads GeoTIFF tiles, mosaics and smooths them, builds the mesh, drapes the map, marches the sun. There is no server and no build step.

The viewer (viewer/viewer3d_template.html → site/index.html)

Draws a terrain model from a folder (radius up to 5 km: beyond 1.5 km the grid coarsens to ⌈2R / 3000⌉ m so it stays ≤ 3000 × 3000 — a 3 km view is a 2 m grid): 1 m DTM GeoTIFF tiles (one UTM zone, EPSG 258xx / 326xx, Float32 or integer) plus any .geojson / .kml / .kmz overlays (polygons draped on the terrain, points as needles; a point with role = steepest is not drawn) and an optional scene.json (title, lat, lon, radius, sigma — the suggested smoothing in m, 0 = off).

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