About

Topographic maps encode elevation as color intensity. Misreading contour intervals or misjudging vertical scale leads to flawed site assessments, incorrect drainage planning, and costly engineering errors. This tool extracts a heightmap from any 2D image by computing per-pixel luminance L = 0.299R + 0.587G + 0.114B, then constructs a triangulated mesh rendered in real-time via WebGL with Phong shading. Vertical exaggeration E is user-adjustable from 0.1× to 5.0×. The tool assumes brighter pixels represent higher elevation. Grayscale heightmaps (DEM exports, NASA SRTM tiles) yield the most accurate results. Color photographs or satellite imagery will produce approximate terrain based on overall brightness, not true elevation data.

Formulas

Luminance (grayscale height) is extracted from each pixel using the ITU-R BT.601 weighted sum:

L = 0.299 ⋅ R + 0.587 ⋅ G + 0.114 ⋅ B

where R, G, B are the red, green, and blue channel values in the range [0, 255]. The vertex height is then:

y_i,j = L_i,j255 × E

where E is the vertical exaggeration factor. Per-vertex normals for Phong shading are computed via central finite differences on the heightmap grid:

n_i,j = normalize(h_i−1,j − h_i+1,j, 2, h_i,j−1 − h_i,j+1)

The perspective projection matrix uses field-of-view θ = 45°, near plane z_n = 0.1, and far plane z_f = 100. Camera orbits using spherical-to-Cartesian conversion: x = r ⋅ sin(φ) ⋅ cos(θ), y = r ⋅ cos(φ), z = r ⋅ sin(φ) ⋅ sin(θ).

Reference Data

Heightmap Source	Resolution	Coverage	Vertical Accuracy	Format
NASA SRTM	30m	Global (60°N - 56°S)	±16m	GeoTIFF / HGT
ASTER GDEM v3	30m	Global (83°N - 83°S)	±8.68m	GeoTIFF
ALOS World 3D	30m	Global	±5m	GeoTIFF
USGS NED	10m	USA	±1.55m	GeoTIFF / IMG
EU-DEM v1.1	25m	Europe (EEA39)	±2.9m	GeoTIFF
LiDAR (Airborne)	0.5 - 2m	Regional	±0.15m	LAS / LAZ
Mapbox Terrain RGB	5m (zoom 15)	Global	±10m	PNG (RGB-encoded)
Copernicus DEM	30m	Global	±4m	GeoTIFF
ETOPO1	1.8km	Global (incl. ocean)	±10m	NetCDF / GeoTIFF
GEBCO 2023	450m	Global ocean bathymetry	±100m	NetCDF
TanDEM-X DEM	12m	Global	±2m	GeoTIFF
JAXA DSM	5m	Japan	±5m	GeoTIFF
Swiss ALTI3D	2m	Switzerland	±0.5m	GeoTIFF / XYZ
OpenTopography LiDAR	1m	Various regions	±0.1m	LAS / Raster

Frequently Asked Questions

The converter derives elevation from pixel luminance. Satellite photos contain color information that does not correlate with elevation - a snow-capped peak (white, high luminance) converts correctly, but a dark forest at high altitude registers as a valley. For accurate results, use single-channel grayscale Digital Elevation Model (DEM) exports where brightness linearly maps to height.

A grid of 128×128 vertices (32,768 triangles) renders at 60 FPS on most devices and suffices for overview terrain. 256×256 (131,072 triangles) captures fine ridgelines. 512×512 (524,288 triangles) approaches the limit for smooth WebGL interaction on mid-range GPUs. Beyond that, frame drops are likely without level-of-detail techniques.

The exaggeration factor E multiplies all Y-coordinates in the exported mesh. An E of 2.0 means a pixel with luminance 128 (normalized to 0.502) gets a vertex height of 1.004 instead of 0.502. If you plan to 3D-print the model or use it in a CAD tool with real-world units, set E to 1.0 and scale afterward in your target software.

Mapbox Terrain RGB encodes elevation in all three channels using the formula: elevation = −10000 + (R × 256² + G × 256 + B) × 0.1. This tool uses standard luminance weighting, which will not decode RGB-encoded elevation correctly. Convert the tile to a grayscale heightmap first using the Mapbox formula, then upload the result.

The OBJ export uses a right-handed coordinate system with Y-up. The mesh spans from (−0.5, 0, −0.5) to (0.5, E_max, 0.5) in normalized units. Vertex normals are included for smooth shading. No UV coordinates or material files are generated; the mesh is geometry-only.

Most heightmap images have black (zero-height) borders or anti-aliased edges from cropping. These create artificial cliffs at terrain boundaries. Crop your source image to remove padding, or use an image editor to feather the borders to match the average terrain height before uploading.