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Flatten SF, a web tool by Drew Edwards, calculates routes between San Francisco locations and lets users weigh distance against cumulative climbing. Its creator says calculations run in the browser using USGS lidar elevation data and a street graph based on Overture and OpenStreetMap.
Drew Edwards has published Flatten SF, a web tool that compares walking or biking routes between San Francisco locations by both distance and cumulative climbing. The tool is designed to help users choose between a shorter route and one with less ascent, using elevation and street-network data processed in the browser, according to the project website.
Users enter a starting point and destination, then move a slider across route options that balance distance against climbing. Flatten SF says the options shown are routes that are not beaten by another option on both measures: a route may be shorter but involve more climbing, or flatter but take longer. Moving the slider to the right does not shorten a route or add climbing, the site says.
The site describes its calculations as running in the user’s browser across more than 160,000 street segments. It uses USGS one-meter lidar elevation data and a street graph based on Overture and OpenStreetMap, according to the project description. The site also says its place search works offline because San Francisco streets, intersections, places and addresses are built into the page.
Climbing is measured as cumulative elevation gain, rather than the net elevation difference between the route’s endpoints. Flatten SF says stairways are included for walking routes and excluded for bike routes. Faint lines on the map show other route options along the distance-climbing trade-off.
Choosing Between Distance and Climbing
San Francisco’s steep streets can make a route’s mileage an incomplete guide to how demanding it may feel. By showing distance and cumulative ascent together, Flatten SF gives users a way to compare route choices before setting out, rather than relying only on the shortest path.
The tool may be useful for people planning a walk or ride who want to limit climbing, though it does not establish which route is safest, most accessible, or easiest in real-world conditions. Users still need to account for factors not described in the site’s route criteria, including traffic, street conditions and personal mobility needs. The project’s value is its presentation of a specific trade-off, not a guarantee about how a route will feel.
bike GPS computer with elevation tracking
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How Flatten SF Builds Routes
Flatten SF describes its route selection as a set of options that are not surpassed on both measures at once. This means it does not simply label one path the best: instead, it displays alternatives from a shortest route to routes that involve less climbing but take longer. The slider’s stated rule is that moving toward flatter options will not produce a shorter route or additional ascent.
The site explains its trade-off using a setting in which one foot of climbing costs 200 feet of walking. It describes this as the point beyond which the alternatives stop being routes, but the source does not provide further detail about how that threshold was selected. Elevation gain counts each uphill segment along the way, so a route that ends near its starting elevation can still have substantial cumulative climbing.
Edwards identifies himself as the creator and links to the tool’s source, data and full analysis. The supplied project description does not give a launch date or report user numbers, testing results or comparisons with other mapping services.
“Routes are computed in your browser over 160,000 street segments.”
— Flatten SF project website
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Limits of the Route Data
The project description does not say how frequently the underlying street or elevation data is updated, or how the tool handles temporary closures, construction, roadworks or changes to access. It also does not provide independent accuracy testing or explain how route results compare with other mapping products.
Flatten SF’s stated measures are distance and cumulative climbing. The available information does not establish that its routes account for pavement quality, crossings, traffic, lighting, bike-lane conditions or wheelchair accessibility. It is also unclear whether the offline search feature means all route calculations work without an internet connection, or only that location search data is stored in the page.
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Further Details From the Project
The project website links to source code, data and a full analysis, where readers can look for more information about the method and inputs. The supplied material does not announce a schedule for updates, new features or expansion beyond San Francisco.
For now, the next practical step for users is to enter two locations and compare the displayed options against their own needs. Anyone relying on a route for accessibility or safety should verify current conditions independently; the tool’s description does not claim to assess those factors.
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Key Questions
What does Flatten SF do?
It compares routes between San Francisco locations by distance and cumulative climbing, allowing users to choose among alternatives with different trade-offs.
What data does the tool use?
The project website says it uses USGS one-meter lidar elevation data and a street graph based on Overture and OpenStreetMap, covering more than 160,000 street segments.
Does the tool include stairs?
According to the project description, stairways are included for walking routes and excluded for bike routes.
Does a flatter route always take longer?
Not necessarily. The tool shows options across a distance-and-climbing trade-off. Its stated slider rule is that moving toward flatter options will not shorten the route or add climbing.
Does Flatten SF check route accessibility or current street conditions?
The supplied project description does not say that it checks accessibility, closures, traffic or street conditions. Users should verify those details separately.
Source: hn
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