Southern California is a short list of big harbors with long open water between them. Los Angeles Outer Harbor, Long Beach and San Diego Bay are working commercial ports, and most of a weekend here is spent either inside a breakwater or on the far side of a crossing, off Santa Catalina or further out at Santa Rosa and San Miguel. What sits under you in between is mostly rock. The chart for this region carries 2,989 charted underwater rocks against 269 wrecks, and that comparison is the one to hold onto. The thing that hurts a boat here has been in the same place since the survey. You find it by drawing a line too close to it.
Helm builds the Southern California pack from 76 official NOAA ENC cells and it comes down at 12 MB. Inside are 62,883 individual soundings, 5,524 charted depth areas, 6,289 depth contours, 589 lights, 154 lateral buoys, 158 lateral beacons, 132 dredged areas and 112 charted anchorages. There are also 39 NOAA tide prediction stations inside the region, from Point Arguello at the northwest corner to Imperial Beach at the south end.
Underwater rock is the category where this region sits high. 2,989 of them are charted here, which puts Southern California 7th of the 18 US regions Helm packs. Wrecks come to 269 and charted obstructions to 908, so rock outnumbers both other hazard classes combined.
That difference is not cosmetic. A wreck breaks up, shifts in a bad season and gets resurveyed. A charted rock is the same rock at the same depth it was last year, so the danger here is fixed and already written down, and the only variable left is how close you pass it.
So on a plan in this region the distance to the charted hazards is the figure to read. When a leg runs within 100 m of them for a stretch, Helm says so and gives the length of the stretch, which at chart scale is a band you would otherwise never notice. The survey grade carried inside the chart matters for the same reason. It states how much of the ground between the soundings was actually measured, and rock is exactly the kind of thing that hides in that gap.
| In the chart pack | Count |
|---|---|
| NOAA ENC cells | 76 |
| Charted soundings | 62,883 |
| Depth areas | 5,524 |
| Depth contours | 6,289 |
| Lateral buoys | 154 |
| Lateral beacons | 158 |
| Charted lights | 589 |
| Anchorage areas | 112 |
| Bridges | 183 |
| Overhead cables | 20 |
| Dredged areas | 132 |
| Charted wrecks | 269 |
| Charted obstructions | 908 |
| Underwater rocks | 2,989 |
| Restricted areas | 324 |
| NOAA tide prediction stations | 39 |
Counted from the Helm chart pack for Southern California, built from official NOAA electronic navigational charts. The pack downloads at about 12 MB.
132 dredged areas are charted in this region and their depths do not cluster. The shallowest reads 0.7 m, the deepest 16.6 m, and the median sits at 5.0 m. One word is covering ship water and a small entrance you could touch bottom in at the wrong hour.
The median is the number worth remembering, because half of the dredged water in Southern California is shallower than 5.0 m. Helm reads the charted value for the dredged area you are in and puts it against the draft you entered, so the deep commercial channel and the thin harbor edge do not come out as the same shade of blue.
183 bridges and 20 overhead cables are charted in the same box. Overhead clearance is checked against the air draft you entered, and where a bridge carries no clearance figure in the chart Helm reports it as unknown instead of printing zero.
NOAA publishes 39 tide prediction stations inside this region, and here the spacing matters more than the count. The height at a mainland pier is not the height at an island anchorage a crossing away, and the back of a big harbor is not its outer basin. The station list runs like this:
The other figure that places high here is anchorage. 112 anchorage areas are charted in this region, 6th of the 18 regions in the app. Against them sit 324 restricted areas and 14 marine farming areas.
Both counts belong on the same plan. Where you may stop and where you may not go are both chart objects in this water, and a route drawn on depth alone is reading half of it. Helm steers a leg around a restricted area and then tells you how much of it the straight line would have crossed, so the detour is one you can look at and overrule rather than a line that quietly bends.
Coming back in from offshore, the safe water marks are the objects that put you on the correct approach, and 13 of them are charted across the whole of Southern California. That is a small set to work from. Everything else that is lit does its work after you are lined up: 589 charted lights, 154 lateral buoys and 158 lateral beacons, most of it inside the channels.
All of it lives in the 12 MB pack, which means the marks are on the screen at the entrance at two in the morning with no signal on the phone.
These counts describe what the chart pack carries, not the state of the water today. Charted data ages, channels shoal and marks move. Keep a lookout and verify locally.
Avalon and Catalina Harbor are both NOAA prediction stations and both are in the Southern California pack, along with Bechers Bay on Santa Rosa Island and Cuyler Harbor on San Miguel Island. The region carries 39 stations in total, so the height you read at an island anchorage comes from a station on that island rather than from a harbor gauge across the channel.
Yes. The pack carries 2,989 charted underwater rocks, 908 obstructions and 269 wrecks, which puts this region 7th of the 18 US regions for rock. Because rock outnumbers wrecks and obstructions combined here, Helm calls out a leg that runs within 100 m of charted hazards and reports how long that stretch is.
132 dredged areas are charted in the region. The shallowest carries 0.7 m, the median is 5.0 m and the deepest is 16.6 m, so the same word covers ship channel and small harbor entrance. Helm reads the charted value for the area you are in and puts it against your own draft.
Helm Boating