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Flatten SF is an interactive tool for finding routes between San Francisco locations and comparing how far they are with how much they climb. Its creator says routes are calculated in the browser using elevation data and a street network, with options for walking and biking.
Drew Edwards has published Flatten SF, a browser-based route planner that compares paths between San Francisco locations by distance and climbing. The tool lets users move along a range of route options, from the shortest path to flatter alternatives, and is intended to show the trade-off for people planning to travel on foot or by bike.
According to the Flatten SF website, route calculations run in the user’s browser across more than 160,000 street segments. The underlying inputs include U.S. Geological Survey lidar elevation data at 1-meter resolution and a street network assembled from Overture and OpenStreetMap. The site says its search for San Francisco addresses, places and intersections is built into the page and works offline.
A slider presents routes along a distance-and-climbing trade-off. At one end is the shortest route; moving toward flatter choices does not shorten the route or add climbing, according to the site’s description. Its stated weighting treats one foot of climbing as equivalent to 200 feet of walking distance. The tool counts cumulative elevation gain along a route, rather than simply comparing the elevations at its endpoints.
Flatten SF also distinguishes between travel modes: stairways are included for walking and excluded for biking. Faint lines on the map represent other routes along the trade-off. The source page identifies Edwards as the creator and links to source data and a fuller analysis, but the material provided does not include performance tests or independent evaluation of the routes.
Choosing Between Climb and Distance
San Francisco’s steep streets can make the shortest route a difficult choice for someone trying to limit climbing. Flatten SF makes that trade-off visible rather than presenting a single path as the only answer: users can compare a more direct route with alternatives that involve less cumulative ascent. That may be useful for walkers who want to reduce uphill effort and for cyclists seeking a route that avoids stairs.
The tool’s value depends on how well its mapped routes reflect conditions on the ground and whether its weighting matches a user’s needs. Its stated rule—200 feet of walking distance per foot climbed—is a design choice, not a universal measure of exertion. The route comparison can inform a decision, but users may also need to account for factors not described on the source page, such as current street closures, surface conditions and personal mobility needs.
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How Flatten SF Builds Routes
The source describes a route graph built from Overture and OpenStreetMap street data, paired with USGS elevation measurements. It says the calculations happen locally in a web browser, while location search uses San Francisco place, address and intersection data packaged into the page. The supplied material does not give a publication date, so the tool’s launch timing cannot be stated more precisely.
Rather than ranking routes solely by distance, Flatten SF displays paths that are not beaten by another option on both distance and climbing. In practical terms, a route remains in the set when a shorter alternative would require more ascent, or a flatter alternative would take longer. The slider moves across that set, with the site describing its far end as the flattest route still worth walking under its chosen trade-off.
“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 website
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Limits of the Route Data
The supplied source does not report independent accuracy checks, how often its street and elevation data are updated, or whether its routes account for temporary construction, access restrictions or changing conditions. It also does not specify how the tool handles every type of path beyond its stated treatment of stairways. Users should treat the displayed options as route-planning information, not confirmation that a route is currently open or suitable for every traveler.
The 200-to-1 distance-to-climb weighting is explained, but the source does not say whether users can adjust it or how the tool defines the point beyond which a flatter route no longer counts as worth walking. The page links to a full analysis and source data; those materials could answer technical questions not covered in the provided description.
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Testing Routes on the Ground
Flatten SF is available as a web page, and the next practical step for users is to enter two San Francisco locations and compare the route options for their travel mode. Before relying on a result, travelers can check current access and street conditions through relevant local sources. The website links to its source data and full analysis, which may provide further detail about its calculations; the supplied report does not announce a schedule for updates or additional features.
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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 explore alternatives to the shortest path.
What data does the tool use?
The site says it uses USGS 1-meter lidar elevation data and a street network based on Overture and OpenStreetMap, covering more than 160,000 street segments.
Does the route calculation work offline?
Flatten SF says its search for San Francisco addresses, places and intersections is built into the page and works offline. The supplied description does not clarify every condition needed to calculate or display a route without an internet connection.
How does it handle stairs?
According to the site, stairways are allowed for walking routes and excluded for bike routes.
Does the flattest option always mean the best route?
No. Flatten SF presents a trade-off shaped by its stated weighting of one foot of climbing for 200 feet of walking. Whether that balance suits a particular traveler depends on their needs, and the route data may not reflect current closures or conditions.
Source: hn
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