• Sonoma Valley Regional Park (map)
  • 38.35231120506429, -122.52076320390259
  • Glen Ellen, CA, 95442
  • United States

2024 Nav-X Challenge @ Sonoma Valley

Quick Info

  • Date: Monday, 1 April to Friday, 31 May; Suggested race time is Saturday, 11 May at 10am. Pre-printed maps will be available.

  • Location: Sonoma Valley, CA

  • Courses: 3h & 6h GPS Map Trek

  • Start location: 38.3523, -122.5205

  • Price: $14 (3h) & $20 (6h)




Get a double dose of Nax-X this April, our second event of 2024 opens on April 1!

  • We have set up a course with 53 checkpoints on an updated topo map in the Sonoma Valley area near Glen Ellen, CA.

  • The event is designed for you to get as many checkpoints as you can in either 3 or 6 hours. The course will extend farther west than the 2022 course to the upper reaches of the map near the summit of Sonoma Mountain.

  • Our suggested race time is Saturday, 11 May at 10am. We will have a Nav-X team member there to hand out pre-printed maps (no extra charge) if you register by May 9. Since this is not an official event, there will be no signage so just meet the Nav-X staff member at the start triangle on the MapRun course 30 min before the mass start time of 10am.

  • We will be using a Smartphone app named “MapRun” to record your visit to each checkpoint. The app will record a “punch” automatically using your GPS position.

  • Results from each competitor are tabulated into a results list.

  • All the instructions including directions to the Start are below. Be safe and have fun!

Register now at https://eventreg.orienteeringusa.org/eventregister/register/start/2024-nav-x-2



Event Information

  • MAPRUN - Please see this page for instructions on how to use the MapRun smartphone app.  It’s important that you load the course while you still have Internet service.  Search for “2024 Nav -X GPS Map Trek Sonoma Valley” and pick the right course (3 hr or 6 hr). Or you can click one of the links provided above to load the course.

  • DIRECTIONS TO START: The start/finish is located closest to this parking spot. (The start/finish is just far enough from the parking area so that you don’t accidentally trigger it when you park or doing loops on the course). From highway 101 or I-80, take highway 37 to highway 121 near Napa and head north. After 6.6 miles, continue straight onto highway 116 for 1.6miles, then take a slight right on Arnold Drive. Continue on Arnold Drive for 7.4 miles, passing through Sonoma Developmental Center (SDC) buildings and crossing a bridge over Sonoma Creek. 

  • PARKING  - Park along the east side of Arnold Drive after crossing the bridge. The parking here is free, but it is possible that all parking spots will be taken on popular weekends. If this is the case, turn around and drive south and park in one of the Sonoma Developmental Center lots. Be sure to obey all parking signs as many lots in SDC are not open to the public.

  • BATHROOMS - There are portapotties and a water fountain in the Sonoma Valley Regional Park parking lot on Highway 12 at the north end of the map but nothing near the start/finish area. There may be bathrooms available in the Sonoma Developmental Center buildings.

  • GEAR RECOMMENDATION - We recommend participants bring the following:

    • Smartphone - goes without saying since we are using an app for timing

    • Compass

    • Long pants or at least gaiters for the tall grass, brush, and poison oak

    • Snacks & Water, especially if you are on the 6-hr course

    • Whistle for safety

  • TRASH - While on the course, practice Leave No Trace (LNT) - bring all trash back to the parking area.

  • BE DISCREET - We don’t have a permit to use any of the parks so try not to be too noticeable when entering or exiting off-trail areas.



MAP & COURSE NOTES

  • VENUE - The event venue comprises 3 separate “parks”: Sonoma Valley Regional Park, Sonoma Developmental Center (SDC), and Jack London State Historical Park. Sonoma Developmental Center served as a state institution for the developmentally disabled for 130 years but has recently been decommissioned. There is a campus of buildings on both sides of Arnold Drive and 2 areas of mostly undeveloped land, the Lake Suttonfield area east of Arnold Drive and the area west of Arnold Drive up to Fern Lake. There is an ongoing effort to determine what will happen with the property (930 acres, 3.8 km^2) but in the meantime, it is open to the public. In a new development, the SDC open space land west of Arnold Drive has been transferred to Jack London SHP. There are some old signs which say no trespassing, etc. but you can ignore them. The map accurately shows what is open to the public and what is forbidden. 

  • PROHIBITED AREAS: Residences, maintenance yards, etc. Observe the restricted areas (hashed purple lines on map). 

  • TERRAIN - Open grassland, oak wooded areas, redwood forests, and some built up areas with roads. The area is split into 2 sections. The area east of Arnold Drive (Sonoma Valley Regional Park and the Lake Suttonfield part of SDC) is a lovely, open grassland and oak wooded area which features a beautiful lake (reservoir). It is not too steep, very runnable, and has little poison oak. The area west of Arnold Drive (SDC + Jack London State Park) is also beautiful this time of year but quite a bit more rugged. It is steeper, thicker, and has more poison oak. But it does have some beautiful groves of redwood trees which tend to grow in the deep valleys.

  • MAP - The map was just created in March 2022 and updated in March 2024. It has 5 meter contours, vegetation density (3 shades of green), cliffs, and water features based on high quality LIDAR data. Roads, trails, fences, and other features were added using Google aerial imagery, Open Street Map, and Strava Global heatmap. Other features were added and adjusted during field checking but the map lacks most orienteering-level detail such as boulders, knolls, rootstocks, single trees, etc. The dark green is in fact pretty thick and should be avoided. One important point to note is that the narrow ride symbol is used to denote an old road grade. These are generally overgrown with no trail but are still useful for navigation.

  • COURSE - The course was designed by Heidi Cusworth and the checkpoints were visited by Bill Cusworth. There are 53 checkpoints varying in point value from 10 to 100 points. The approximate straight-line distance to get them all is about 21 km. Generally, higher value controls are farther from the start, harder to find, or some combination of both.

  • POISON OAK - There are some small poison oak areas in the area east of Arnold Drive, but are avoidable on this course. However, the west side of Arnold Drive has considerable poison oak, except for the high elevation open areas near the western edge of the map. Most of the poison oak is a shin-high carpet that covers about 75% of the forested areas. It’s best to devise routes that take advantage of roads/trails, open areas, and spurs as much as possible and avoid crossing creeks in the forested areas. You’ll definitely want to wear long pants and/or gaiters as it is impossible to avoid on several legs. If you are really allergic, it is recommended to stick to the east side of the map.

  • START - The start area is shown on your map as a triangle and is on a trail just east of Arnold Drive. Do not approach the start until you are ready to go! Your GPS device will start you automatically and alert you by beeping once you are within ~15 meters of the spot. 

  • SCORING:  Just like our other events, each checkpoint has a point value reflecting the difficulty (higher point value for tougher checkpoints).  The point value is the “10 part” of the checkpoint code.  Examples:  33 = 30 points, 50 = 50 points, 88 = 80 points, etc. Late penalty is 10 points per minute or any part of a minute (1:01 late = -20 pts)

  • MARKERS - All checkpoints are marked with one piece of biodegradable ORANGE flagging with “Nav-X” written on it. Be aware though that as time goes by, animals and hikers may remove some of the flagging, so it is not guaranteed to be present. The start/finish does not have flagging because it is in a public place.

  • FINISH - the finish is marked on your map with a double circle and is located at the same place as the start. When you are within ~15 meters of the spot, your GPS device will register a finish. Do not approach the finish until you are ready to end your course. (Depending on the device, it may be possible to continue the course after this, for example if you approached the finish spot by accident. However, this might not work for you, so we recommend you don’t go near the finish until you are done.) Remember to upload your result after you finish (if it doesn’t happen automatically).

  • MAP PRINTING - You will need to print your own maps. We are providing a Zip file with the map documents in PDF format. The text control descriptions are on the map, and we are also providing a separate PDF with the symbolic control descriptions. The Zip package contains 3 files: the course map at 1:15,000 scale (portrait format, 2 pages),  the course map at 1:10,000 scale (landscape format, 4 pages), and separate symbolic control descriptions.


If you want to report any problems with the course, please email info@navxchallenge.com. Also, here’s a link to some pictures of the area.

Important Safety Info

  • YOU ARE DOING THIS AT YOUR OWN RISK - WE TAKE NO RESPONSIBILITY FOR ANY INJURIES OR DEATH.  HAZARDS INCLUDE STEEP HILLS, LOOSE ROCKS, CLIFFS, OCCASIONAL DENSE AND SHARP BRUSH, POISON OAK AND RATTLESNAKES.

  • CELL COVERAGE - There is cell phone coverage in most locations on the map.

  • WHISTLE - Due to the self-serve format, you may be completely on your own when you run your course. Be aware of this! You should bring a whistle in case of an emergency.  

  • WATER - There are no open water spigots at the start/finish. The creeks are very full and there are several ponds on the map but the water should be treated before drinking. It is recommended to bring all the water you need with you.

  • FENCES - Do not try to climb over fences, ONLY go under.

  • ROAD CROSSING - The course takes you on both sides and (most likely) along Arnold Drive, a busy road. Be careful when crossing.

  • POISON OAK - is very prevalent on the west side of Arnold Drive, except for the open areas on the far west portion of the map. See map notes for more details.

  • TICKS - are present at this time of year and were encountered during course setting.

Thanks for reading, and have fun! - Bill & Heidi and the Nav-X team