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A web tool called Flatten SF lets users compare routes between San Francisco locations by distance and cumulative elevation gain. Its route calculations run in the browser and draw on USGS elevation data and the Overture and OpenStreetMap street graph. The site describes a trade-off slider, but its accuracy and route recommendations have not been independently verified.
Flatten SF, a web-based route planner for San Francisco, lets users compare paths between two locations by distance and cumulative climbing. The tool says it calculates routes in the browser using more than 160,000 street segments and elevation data, offering a way to weigh a shorter trip against a less hilly one.
The site presents a slider spanning the trade-off between shortest and flattest routes. According to Flatten SF, each position represents a route that is not beaten by another option on both distance and climbing. Moving the slider to favor less climbing does not produce a shorter route or add climbing, the site says. It describes one point on the scale as treating a foot of climb as equivalent to 200 feet of walking; beyond that, routes stop being practical walking routes by the tool’s definition.
Flatten SF says route calculations are performed in the user’s browser, using USGS one-meter lidar elevation data alongside the Overture and OpenStreetMap street graph. The site also says faint lines display alternative routes along the distance-climb trade-off. Place search is built into the page for San Francisco intersections, addresses and places, and works offline, according to the project description.
The tool distinguishes between travel modes: stairways are allowed for walking and excluded for biking. Climbing is measured as cumulative elevation gain along a route, rather than simply the net elevation difference between its starting and ending points. The site credits the project to Drew Edwards and links to its source, data and full analysis.
Planning Around San Francisco Hills
San Francisco’s steep streets can make two routes of similar length feel very different. By putting distance and uphill gain on the same screen, Flatten SF gives residents and visitors another way to plan trips around the physical effort they are willing or able to take on. That may be useful for walkers seeking a gentler path, cyclists comparing alternatives, or anyone trying to understand why the shortest route is not necessarily the easiest.
The feature is a planning aid, not evidence that a particular route is safe, accessible, or suitable for every traveler. The available source describes how its calculations work, but provides no independent evaluation of their accuracy or of whether the routes account for conditions such as construction, sidewalk quality, traffic, or accessibility barriers.
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How the Route Trade-Off Works
Rather than returning a single path, the tool describes a range of routes where distance and climbing are traded against one another. These are routes that, according to the site, cannot be improved on both measures at once: a route with less climbing may take longer, while a shorter option may involve more ascent. The slider lets a user explore that range instead of relying on one default answer.
The elevation measure is cumulative gain. A trip that climbs and then descends can have substantial total climbing even if its destination is close to the starting elevation. The site says its elevation input comes from USGS one-meter lidar, while the streets come from the Overture and OpenStreetMap street graph. It does not provide, in the supplied description, a date for the data or a separate account of how often the street network is updated.
“Routes are computed in your browser over 160,000 street segments.”
— Flatten SF website
Accuracy and Access Details
The supplied project description does not give a publication date, independent accuracy testing, or a comparison with other routing services. It also does not specify when the underlying elevation and street data were collected or how frequently the map is refreshed. Users should not assume the displayed route reflects live conditions: the source does not describe real-time closures, construction, traffic, or sidewalk and path conditions.
The site’s description says the slider covers routes along the distance-climbing trade-off, but the supplied material does not explain every routing constraint or how it handles all possible barriers. It also does not claim that a low-climb route is step-free or accessible. Those details matter for travelers who need an accessible path or must avoid particular surfaces and crossings.
Check Routes Before Traveling
Users can enter two San Francisco locations and adjust the slider to compare the available balance of distance and climbing, with stairways treated differently for walking and biking. The project links to its source code, data and full analysis, where readers can examine more of the method. The supplied material does not announce a release schedule, planned features, or a next update. Travelers should confirm current conditions and accessibility needs through other reliable sources before setting out.
Key Questions
What does Flatten SF do?
It compares routes between two San Francisco locations, showing a trade-off between distance and cumulative climbing rather than only presenting one route.
What data does the tool use?
Flatten SF says it uses USGS one-meter lidar elevation data and the Overture and OpenStreetMap street graph, covering more than 160,000 street segments.
Does a flatter route always take less time?
Not according to the information provided. The tool compares distance and climbing, but the source does not say it estimates travel time. A route with less climbing may be longer.
Does it include stairs?
The site says stairways are included for walking routes and excluded for biking routes. It does not say that routes are step-free or accessible.
Are the routes verified for current conditions?
The supplied description does not mention live updates for construction, closures, traffic, or path conditions, and it provides no independent accuracy assessment. Check current conditions separately before traveling.
Source: hn
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