BRÅVALLA VERSION 8 — SOURCES AND COMPARISON, 2026-10-10

Geometry: © OpenStreetMap contributors, ODbL 1.0.
https://www.openstreetmap.org/copyright
Raw extract: map.osm (bbox 16.065,58.592,16.145,58.636).
Derived database: viewer/bravalla-data.js; reusable under ODbL, separate
from application code. Contains filtered runway, road, building, woodland
and field geometry. Two runway ways: 26725323 (15/33), 26750466 (06/24).
Widths 38 m and 40 m from tags. Start is at mapped southwest threshold
16.0903175 E, 58.6063345 N. True bearing is computed from mapped endpoints;
painted runway designation is magnetic/historical, not the true bearing.

Elevation: Mapzen Terrain Tiles, N58E016.hgt.gz accessed 2026-10-10.
https://s3.amazonaws.com/elevation-tiles-prod/skadi/N58/N58E016.hgt.gz
https://registry.opendata.aws/terrain-tiles/
https://github.com/tilezen/joerd/blob/master/docs/attribution.md
Terrain data courtesy of USGS; Europe terrain produced using Copernicus
data and information funded by the European Union, EU-DEM layers; Mapzen.
Native one-arcsecond raster resampled to 161x161 (about 40 m grid), bbox
16.05,58.585,16.16,58.64. No-data samples would be clamped to zero.
Runway corridors graded using interpolated endpoint elevations. Road and
paint surfaces offset slightly to prevent z-fighting. This is not surveyed
runway slope data. Heights are MSL-style DEM heights, not GNSS ellipsoid
heights; no geoid conversion has been claimed or fabricated.
Terrain outside this local patch remains approximate, not a real DEM.

Photos studied visually in browser, not copied as game textures:
Joshua06, CC BY-SA 4.0, 22 April 2019:
https://commons.wikimedia.org/wiki/File:Bråvalla_Norrköping_april_2019_(34).jpg
Long brown workshop facade with regular windows / vertical bays.
https://commons.wikimedia.org/wiki/File:Bråvalla_Norrköping_april_2019_(27).jpg
Two-storey red-brick administration building, white window frames,
octagonal glazed tower cab and antennas mounted above the roof.
Model comparison: replaced identical hangar row and detached tower with
actual mapped footprints, brick/window rhythm and roof-mounted tower.
Tower placement uses nearby building footprint 670264773 and is an
approximation; camera geotags alone do not survey building position.
Building heights default to 8 m unless height/levels are mapped.

Plan comparison: OSM map at 58.6109 N,16.1036 E, zoom 15; matched crossed
runways, perimeter roads and east-side building cluster against view 9.
Photorealistic roof/wall textures and exact historical reconstruction
remain future work. Current OSM geometry and 2019 photos are not a
single coherent historical year. Mission treats the closed base as active.

GeoJSON export: viewer/bravalla.geojson, same 1177 filtered OSM ways as
the WebGL scene. WGS84 lon/lat, polygons and lines, OSM way IDs and tags.
This export does not include OSM multipolygon relations or DEM heights.
Regenerate both JS and GeoJSON with scripts/build_bravalla_data.py.
