Course map, elevation profile & surface
Fly the course
Follow the route over 3D terrain, mile by mile.
Race-day light
For a 13:45 finish (an estimate) · starting 7:00 AM Mar 19 · headlamp mi 58–the finish. Dark means the sun below civil twilight.
Climbs
15 climbs · 10,874 ft totalbiggest firstElevation gain, measured two ways
| Source | Gain | vs lidar |
|---|---|---|
| Course file (GPX) | 12,998ft | +7% |
| USGS lidar, 1 m | 12,107ft | reference |
They differ because a GPS file picks up noise on every wiggle and often takes its heights from a coarse terrain model, while lidar maps the ground itself to about a metre. We sampled this route every 98 ft against USGS 3DEP and counted each rise of 10 ft or more, on Oct 25, 2026. The planner still uses the course file.
Aid stations as published on the course file
| Aid station | Mile | km |
|---|---|---|
| START - Fort Baker | 0.0 | 0.0 |
| A AS1 - Rodeo Beach | 6.6 | 10.5 |
| A AS2 - Muir Beach | 12.4 | 20.0 |
| A AS3 - Cardiac Hill | 19.6 | 31.6 |
| A AS4 - Stinson | 22.6 | 36.4 |
| A AS5 - Tam Summit | 30.9 | 49.7 |
| A AS6 - Lagunitas | 36.5 | 58.8 |
| A AS7 - Azalea Hill | 39.9 | 64.1 |
| A AS8 - Fox Hollow | 49.0 | 78.9 |
| A AS9 - Big Rock | 53.8 | 86.6 |
| FINISH - Marinwood Community Ctr | 62.5 | 100.6 |
Badge colours match the markers on the map above — always confirm locations and cutoffs with the race organizer.
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Conditions typical race-day weather for Mar 19 at the start
Typical = the median of 2016–2025 for Mar 19 ±3 days at the start line; a wet day has 1 mm of rain or more. Historical weather from Open-Meteo.
Race almanac the sky on race day
Next race day Fri, Mar 19, 2027 · 7:00 AM start
First and last light are civil twilight, the sun 6° below the horizon. The moon is lit as at midnight after the start; headlamp hours count a typical finish from the start while the sun is below civil twilight. Worked out for the start line.
Reviews what runners who have been there say
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About this course
The Big Alta 100K — 2027 covers 62.5 mi (100.6 km) with 12,998 ft of elevation gain. That is about 208 ft per mile of climbing, and 12,939 ft of descent. The course tops out at 2,388 ft and bottoms out at 10 ft. The surface is 48% gravel, 46% trail and 6% paved. There are 9 aid stations on course; the longest stretch between aid is 9.2 mi. The profile has 15 sustained climbs; the biggest is the climb from mi 22.6, +1,545 ft over 2.7 mi at 10.7% on average (steepest stretch 26%). Race day is March 19, 2027, starting at 7:00 AM; the sun rises at 7:16 AM and sets at 7:21 PM. Typical race-day weather at the start: a high of 59°F and a low of 48°F, with a 31% chance of a wet day. The interactive map above shows the full route with its elevation profile and aid stations, built from the course's GPS file.
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Course history
- Sep 10, 2026Added to the catalog
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