Cesium Terrain Truth Benchmark

Google Photoreal (DSM) vs Copernicus GLO-30 (DEM), 6 of 9 patches

mountain	desert	coastal
urban	airfield	canyon

The green surface is Google Photorealistic 3D Tiles, the orange surface is Copernicus GLO-30.

Results

Headline RMSE in metres:

Patch	vs Cesium WT, Copernicus	vs Cesium WT, 3DEP	vs Photoreal, Copernicus	vs Photoreal, 3DEP	WT vs Photoreal (DSM gap)
open_sky	6.78	5.98	0.70	0.91	6.62
mountain	22.77	37.57	25.20	40.80	11.25
forest	0.56	0.24	3.12	3.01	2.96
desert	8.53	11.15	10.29	13.17	5.41
coastal	21.12	25.35	22.55	26.52	9.86
urban	58.42	1.97	53.08	54.87	54.86
airfield	4.15	1.18	4.02	4.84	4.95
canyon	26.44	35.04	25.59	34.78	10.76
industrial	3.14	2.40	5.06	4.82	5.40

How it works

1. Cesium sampler inside the Isaac Sim 5.1.0: For each patch in /configs/locations.yaml and each configured Cesium source it sweeps a nadir depth probe over a centred ENU grid and writes cache/<location>/<source>.npz plus a metadata sidecar.
2. Host-side comparator: For each location loads Cesium heightfields, samples every configured DEM source at the same ENU grid, converts heights to the WGS84 ellipsoid, runs vertical metrics and writes per-patch reports.

flowchart LR
    LocCfg[configs/locations.yaml] --> Sampler[scripts/sample_cesium_patch.py]
    Docker[scripts/run_sample.sh] --> Sampler
    Sampler --> WTCache["cache/{loc}/cesium_world_terrain.npz"]
    Sampler --> GPCache["cache/{loc}/google_photoreal.npz"]

    SrcCfg[configs/sources.yaml] --> Compare[scripts/compare_dem_to_cesium.py]
    WTCache --> Compare
    GPCache --> Compare
    Compare --> DemReader[terrain_benchmark/dem_reader.py]
    DemReader --> Tile["data/dem/{copernicus_glo30|usgs_3dep}/*.tif"]
    Compare --> Reports["reports/{loc}.json + .txt + .png + .3d.html"]
    Reports --> Gif[scripts/render_3d_gif.py]
    Gif --> GifOut["reports/{loc}.3d.gif"]