TopoLines
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| Author: | Alexis Oulès | |||||||||||||||||||
| License: | Proprietary | |||||||||||||||||||
| Platform: | Web | |||||||||||||||||||
| Status: | Active | |||||||||||||||||||
| Website: | https://www.topolines.app/app | |||||||||||||||||||
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Web app that traces topographic contour lines from cited elevation models (GEDTM30 worldwide, national lidar at 5–10 m) and exports GeoJSON, DXF, SVG or PNG, using OpenStreetMap coastlines to clip contours at the shore. | ||||||||||||||||||||
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TopoLines is a web application that generates topographic contour lines for a user-drawn area anywhere on Earth. Contours are traced from openly licensed digital elevation models and combined with OpenStreetMap coastline data. Results can be exported as GeoJSON, DXF, SVG or PNG.
Overview
The user draws a zone on a web map, chooses a contour interval and trace settings, and the server traces contours from the elevation model that covers the zone. The dataset that served the zone is shown in the interface and written, with its licence credit, into the metadata of every export.
Typical uses include contours for GIS projects, site studies in CAD, cartography and map design, and layered terrain models cut on laser cutters or CNC machines.
Use of OpenStreetMap data
- Coastlines: coastline geometry (
natural=coastline), queried through the Overpass API, is used to clip contours at the shoreline and to mask the sea, since many elevation models report non-zero heights over water. - Basemap: the map used to pick an area is an OpenStreetMap-based vector basemap served by OpenFreeMap.
- Place search: geocoding uses Nominatim.
OpenStreetMap data is used under the Open Database License and credited as "© OpenStreetMap contributors".
Elevation data
| Dataset | Publisher | Resolution | Coverage | Licence |
|---|---|---|---|---|
| GEDTM30 v1.2 (bare-earth DTM) | OpenGeoHub, via OpenTopography | 30 m | Worldwide | CC BY 4.0 |
| Terrain Tiles (GeoTIFF) | Mapzen / Nextzen, AWS Open Data | ~10 m | Worldwide | Open data |
| RGE ALTI | IGN | 5 m | Metropolitan France | Etalab Open Licence 2.0 |
| 3DEP | U.S. Geological Survey | Up to 5 m (from lidar where flown; ~10 m elsewhere) | United States | Public domain |
| swissALTI3D | swisstopo | 5 m | Switzerland | Open data (attribution) |
| LIDAR Composite DTM | Environment Agency | 5 m | England | Open Government Licence v3.0 |
| MDT | Instituto Geográfico Nacional | 5 m | Spain | CC BY 4.0 |
| ALS DTM Österreich | BEV | 5 m | Austria | CC BY 4.0 |
| TINITALY/1.1 | INGV | 10 m | Italy | CC BY 4.0 |
| DGM1 | Bayerische Vermessungsverwaltung, Geobasis NRW | 5 m | Bavaria, North Rhine-Westphalia | CC BY 4.0, dl-de/zero-2.0 |
A national model is used only when the zone lies entirely within its coverage; zones crossing a border use a worldwide model, so a single map is never assembled from two datasets. Users can also upload their own GeoTIFF elevation model.
GEDTM30 is described in Ho, Hengl et al. (2025), PeerJ, doi:10.7717/peerj.19673.
Contour options
- Contour interval (down to 5 m) and index contours
- Smoothing and minimum contour length (to remove small loops caused by elevation-model noise)
- Auxiliary (half-interval) contours on flat ground
- Depression contours marked with inward hachures
- Contour labels, scale bar, north arrow and legend
Export formats
- GeoJSON: each feature carries its elevation and contour type (index, intermediate, auxiliary, coastline). Output CRS: WGS 84 (EPSG:4326), automatic UTM zone, Lambert-93 (EPSG:2154), Web Mercator (EPSG:3857), British National Grid (EPSG:27700), ETRS89 / UTM 30N and 31N (EPSG:25830, EPSG:25831).
- DXF: one layer per contour type, same CRS options.
- SVG: paths grouped by elevation band.
- PNG: up to 3200 px wide.
Licence and access
TopoLines is proprietary software. A free tier (sign-in required) provides the 30 m worldwide model and PNG export; vector formats, higher-resolution national models and larger areas use paid credits.