Jekyll Shallows - GPX Route

(major update 7/24/2016, see below)
I've been through Jekyll Creek a dozen times and although there is a channel with 5.7 MLW depth, the problem has always been how to find it. This time through I found a good fit using ENC charts as displayed on the iPad app, Charts and Tides. I would think that any app that used NOAA ENC charts would display the same route (my laptop with ENC charts showed the route correctly).

At Jekyll Creek just south of the bridge
Sitting at anchor just south of the bridge on 4/22/216, we were astounded when we saw two huge tugs with several hundred feet of dredging pipe go through Jekyll at dead low tide, one tug on each end of the pipes. I followed in my dinghy. The mud stirred up was incredible. They stopped multiple time and rev'ed up the engines and plowed through. It took 20 min to round G19. In other words, they created the channel and successive runs is what keeps the channel open.

After they passed I got in my dinghy to measured the deepest spot by G19, R20 and R20A, going side to side with a portable depth sounder and found that 80 to 100 ft off each mark was best, at least now after the two tug plow team.

Route notes:
- Do not hug any marks, stay off R20A,  R20 and R19 by 80 to 100 ft.
- Garmin charts are useless here but NOAA ENC charts work well.
- The depth readings were taken the day after two tugs passed (plowed!) through.
- A GPX file of the route is available at GPX Routes named BJekyll.
Route depths:
Bridge  10.6 MLW, use as a check on general water depth, the bridge height gauge read 65 ft (it was near high tide when I passed through but all readings have been corrected to MLW)

Heading north:
1/2 way   6.7 MLW
R20A       8.3 MLW
1/2 way   6.2 MLW
R20         6.6 MLW
By docks  9.2 MLW
1/2 way    8.1 MLW
G19          5.7 MLW (80 ft off )
At shoal mark  7.6 MLW
G17         9.1 MLW
R16          7.8 MLW

Deeper the rest of the way north.
I don't claim this is the best route but it worked on 4/22/2016 for 5.7 MLW.

For more background on why the critical turn at G19 can be such a problem, take a look at the charts below.The blue line is the route I took in the spring of 2016 using the GPS coordinates of each chart. For the most part, the spacing between G19 and the route is fairly constant in all the charts, it's the depicted channel that moves around on the chart relative to G19 and the route.


At left is the NOAA raster chart at G19 in Jekyll Creek, greatly over zoomed. Note the position of the G19 mark, it's right in the middle of the shown channel. If you follow the magenta line you would hug G19 (with disastrous results at low tide)

The blue line is the GPX route I followed for the depths listed above. South of G19 it's on the red edge of the shown channel. By G19, it's 100 ft to the west.











At left is the NOAA ENC digital chart of the same area around G19 as displayed by the OpenCPN charting program. The blue line is once again the GPX route I took in the spring of 2016. Note that it's right down the middle of the channel shown on the ENC chart and stands off G19.

The blue line is my GPX route and it passes G19 by 100 feet. G19 is shown correctly positioned in both the ENC and BSB charts, it's just the channel that is shown differently.









At left is the Navionics presentation of the NOAA ENC chart around G19 in Jekyll Creek. Note that it's just like the NOAA ENC chart shown earlier displayed by a different program above.

It's encouraging to note that of several programs I have that display NOAA ENC data, they all show the channel around G19 the same including Navimatics Charts and Tides. It's when the chart manufacturers try to put their own spin on the charts that things seem to get shifted, at least for Jekyll Creek.




At left is the Navionics chart around G19. The channel is shown displaced to the east. The blue line is the GPX route.

If you followed the channel shown you would be too close to G19. For the Navionics two charts, I entered the route and just switched between Govt charts and Navionics charts and took a snapshot of each.








The Garmin chart as shown in their iPad app is at left. If you followed the channel you would be too far away from G19 coming from the north.


I want to emphasize that the NOAA ENC charts are not always correct and in some places they are shifted even more than the Garmin or Navionics charts. In several cases, the Garmin chart is dead on and it's the NOAA ENC charts that are off. No one chart supplier is always correct. NOAA's ENC and BSB charts don't even agree with each other near G19 in Jekyll Creek.

I've been using the GPX route I made from my spring of 2016 run north as the standard for the deepest water. As I've cautioned many times, things change on the ICW. What worked in the spring of 2016 may not work for the deepest water in the fall of 2016. Pay attention to the wind direction (east is good, west is bad) and you may want to check the water level height station at Fernandina to see the general water level in the area. If you find different depths by all means post on Active Captain.