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Flatten SF is an interactive route planner that lets users compare paths between San Francisco locations by distance and climbing. Its creators say route calculations run in the browser and use USGS 1-meter lidar elevation data with Overture and OpenStreetMap street networks. The source does not provide launch timing, independent accuracy testing or details about the team beyond naming Drew Edwards.
Flatten SF is an interactive route planner for comparing paths between locations in San Francisco by both distance and climbing, giving walkers and cyclists a way to explore alternatives to the shortest route. The site says calculations run in a user’s browser across more than 160,000 street segments, using elevation data from the U.S. Geological Survey and street-network data from Overture and OpenStreetMap.
Users enter a starting point and destination, then move a slider across routes representing different trade-offs between distance and cumulative elevation gain. The site describes the options as routes that are not beaten by another route on both measures: a route may be shorter but involve more climbing, or flatter but take longer. Moving the slider to the right, according to the site, does not produce a shorter route or add climbing.
The tool’s description says its flattest setting treats a foot of climbing as equivalent to 200 feet of walking. It calls this the point beyond which the paths “stop being routes,” a design choice explaining how the tool weighs the competing measures rather than a universal standard for walking. Faint lines on the map show other routes along the trade-off.
Elevation is counted as cumulative gain, not simply the difference between the elevations at the start and finish. Stairways are included for walking routes and excluded for bicycle routes, the site says. Place search works offline, using San Francisco streets, intersections, places and addresses built into the page.
Route Choices Beyond the Shortest Path
San Francisco’s steep streets can make two routes of similar length feel very different. By showing distance and climbing together, Flatten SF makes that trade-off visible instead of returning only a single route. That may help people choose a path that better fits their preferences, including travelers seeking less uphill walking or cyclists avoiding stairways.
The tool does not, on the information provided, establish which path is safest, most accessible or quickest in real-world conditions. Its stated measures focus on distance and elevation gain. Users still need to account for factors such as pavement, traffic, construction, weather and individual mobility needs, which are not described in the source material.
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How the Route Model Works
Flatten SF says it combines a street graph from Overture and OpenStreetMap with USGS lidar elevation data at 1-meter resolution. The site reports that it calculates routes locally in the browser across more than 160,000 street segments, rather than describing a server-based route service. Search data for San Francisco is also built into the page, allowing place lookup while offline, according to the site.
The route slider is based on a set of options where no other route is both shorter and lower in climbing. This is a way to present the distance-versus-elevation trade-off; it does not mean every possible trip is equally suitable for every user. The project is credited to Drew Edwards, and its page links to source material, data and a fuller analysis.
“Routes are computed in your browser over 160,000 street segments, using USGS 1 m lidar elevation and the Overture / OpenStreetMap street graph.”
— Flatten SF
Accuracy and Coverage Questions
The source does not state when Flatten SF launched, how often its street and elevation data are updated, or whether route accuracy has been independently evaluated. It also does not explain how the tool handles temporary street closures, construction, sidewalk conditions, private access or accessibility barriers beyond its stated treatment of stairways.
The site’s claims about data, offline search and browser-based processing come from its own description. No independent testing or user results are included in the supplied material, and no details are provided about how cycling routes account for road conditions or traffic. The 200-to-1 walking-to-climbing weighting is presented as the tool’s own threshold; the source does not say that it reflects a user survey or a medical or accessibility standard.
Further Data and Analysis
Flatten SF’s page links to its source, data and full analysis, which could provide more detail on the route model and its inputs. The supplied material does not announce a planned update, expansion beyond San Francisco or a schedule for refreshed data. For now, users can compare route options on the site while treating its figures as guidance based on the stated network and elevation sources.
Key Questions
What does Flatten SF do?
Flatten SF compares routes between San Francisco locations by distance and cumulative climbing, letting users move a slider to explore different trade-offs.
How does it calculate climbing?
The site says it uses USGS 1-meter lidar elevation data and counts cumulative elevation gain along the route, not just the elevation difference between the endpoints.
Does the tool include stairs?
According to the site, stairways are allowed for walking and excluded for bicycle routes. The source does not provide additional details about accessibility conditions.
Can I use its place search offline?
Flatten SF says its San Francisco intersections, places and addresses are built into the page, allowing the place search to work offline.
Is the flattest route necessarily the best route?
Not necessarily. The tool focuses on distance and climbing; its source does not say it evaluates traffic, safety, pavement, closures or every accessibility need. Users should check conditions relevant to their trip.
Source: hn
