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Flatten SF is a browser-based tool for finding routes between San Francisco locations and comparing how far they travel with how much they climb. Its creator says routes are calculated on the user’s device using USGS lidar elevation data and an Overture/OpenStreetMap street graph. The supplied report does not identify a launch date or provide independent testing of the tool’s accuracy.
Flatten SF, a browser-based tool by Drew Edwards, lets users compare routes between San Francisco locations by both distance and cumulative elevation gain. The site says it calculates routes in the browser across more than 160,000 street segments, giving people a way to weigh shorter travel against less climbing.
Users enter a starting point and destination, then move a slider across routes that represent different distance-and-climb trade-offs. According to the site’s explanation, each displayed route is one that cannot be beaten by another route on both measures at once. Moving the slider toward a flatter option does not produce a shorter route or add climbing; instead, it moves along the set of routes where reducing ascent comes at the cost of distance.
The elevation data comes from U.S. Geological Survey 1-meter lidar, while the street network is based on Overture and OpenStreetMap data, the site says. Route calculations run locally in the user’s browser. The site also says place search works offline because San Francisco intersections, places and addresses are included in the page.
Climbing is measured as cumulative elevation gain, not simply the height difference between the two endpoints. The site’s model assigns a walking-distance cost to climbing: at the far-flat end, a foot of ascent is treated as equivalent to 200 feet of walking. It says routes beyond that point stop qualifying as routes. Stairways are included for walking directions and excluded for bicycle routes. Faint map lines show other routes along the distance-climb trade-off.
Choosing Between Distance and Climbing
For people walking across San Francisco, elevation can change how demanding a trip feels even when two destinations are close together. Flatten SF makes that factor visible alongside distance, allowing users to decide whether a longer path with less ascent better suits their needs. That may be useful for walkers planning around hills, people carrying items, or anyone who prefers to limit climbing.
The tool presents alternatives rather than declaring one route best for every traveler. Its slider makes the trade-off explicit: selecting less climbing can mean walking farther. That distinction matters because a route optimized for flatness may not be the quickest or shortest choice, and users still need to judge conditions such as traffic, accessibility and surface quality.
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How Flatten SF Builds Routes
The source describes a route planner focused on San Francisco and its steep street network, rather than a general-purpose navigation service. It combines a street graph with detailed elevation measurements to compare routes between points. The calculation is described as browser-based, and the site says its built-in search data allows place lookup without an internet connection.
Its route options are based on a specific mathematical trade-off between distance and climbing. The site calls the displayed options routes that are not surpassed on both measures by another available route. The 200-feet-per-foot figure is part of the tool’s stated weighting for the flattest option, not a claim that all users experience elevation in the same way. The supplied report credits the project to Drew Edwards and links to source data and a fuller analysis, but gives no publication or launch date.
“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 supplied information does not state when Flatten SF launched, how often its street and elevation data are updated, or whether the routes have been independently checked against on-the-ground conditions. It also does not provide measured accuracy figures or explain how the tool handles temporary closures, construction, steps that are inaccessible, or other changing street conditions.
The site describes the data sources and route logic, but the report does not establish how well the results serve different users, including people using wheelchairs or mobility aids. Its walking mode permits stairways, while its bicycle mode excludes them; the available description does not specify a separate accessibility setting or guarantee that a low-climb route is fully accessible. Those details should not be assumed from the elevation comparison alone.
Checking Routes Before a Trip
Users can enter two San Francisco locations and compare the available routes on the site’s distance-and-climb slider. Before relying on a result for a particular journey, they should check current street conditions and confirm that the route fits their mode of travel and mobility needs. The source links to the project’s data and full analysis, which are the places to look for further details about its methods.
No future release, update schedule or additional feature is identified in the supplied report. Whether the creator will publish testing results, expand the map beyond San Francisco or add accessibility-specific routing remains unknown.
Key Questions
What does Flatten SF do?
It compares routes between San Francisco locations by walking distance and cumulative elevation gain, letting users choose a point along that trade-off.
How does the tool measure climbing?
According to the site, it totals cumulative gain across the route, rather than calculating only the elevation difference between the starting point and destination.
What data does Flatten SF use?
The site says its calculations use USGS 1-meter lidar elevation data and a street graph from Overture and OpenStreetMap, covering more than 160,000 street segments.
Does the flattest route always take less time?
No such guarantee is given. The tool compares distance and climbing; it does not state that its flattest option is the fastest, and choosing less ascent may mean walking farther.
Can cyclists use the route planner?
The site says stairways are excluded on a bike and allowed on foot. The supplied description does not provide further details about bicycle-specific routing or accessibility features.
Source: hn
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