Resources
Google Maps
The “Earth” option (click on lower left corner button, “Earth”) displays a satellite view of the map (or a 3-dimensional globe with the location highlighted.)
You can also enter a latitude and longitude. For example, enter “41 26.00 - 44 13.10” (without quotes) in the search field and it will show you a location in the middle of the North Atlantic Ocean. This would be useful if you are planning an offshore cruise and intend to mark your proposed course on the map.
Waterway Guide
Tide and Current
Windfinder
The iPad app (Windfinder Pro) displays, on a 3-hour basis, wind direction/speed, cloud cover, temperature, wave direction/height, and tide condition. All this information for ‘today’ and forecast for the next 9 days. Access this the day before you start and print.
Magnetic North (compass), True North (charts) & Declination
What is Declination?
“Magnetic declination, sometimes called magnetic variation, is the angle between magnetic north and true north. Declination is positive [if magnetic north is] east of true north and negative when west. Magnetic declination changes over time and with location.“
Finding Declination
Go to this site to find the declination anyplace in the world and enter the location of your ‘cruise’.
Calculation example:
If the declination is 12°, 34'' W, I’d use -13° for our piloting purposes. Here are the formulas to use:
Magnetic North = True North – Declination
If the azimuth on the chart is 327°t, then
Degrees magnetic = 327 minus (-13)
X°m = 327 - (-13)
= 340°m, the heading I would use on the compass.
True North = Magnetic North + Declination
If my compass reads 340°m, then
Degrees true = 340 plus (-13)
X° t = 340 + (-13)
= 327°t, the azimuth I would plot on the chart.
A Row Cruise Example
Google Map of Proposed Route |
The launch site I’ll use is on the east end of Cedar Run Dock Road, so I print a chart, using the Waterway Guide that includes the launch site and Manahawkin Bridge.
Waterway Guide Chart: Launch Site to Manahawkin Bridge |
Rowing north in the Bay, I’ll go from Manahawkin Bridge to Sedge Island and I print that portion of the route.
...Manahawkin Bridge to Sedge Island |
The next chart I print goes from Sedge Island up to Barnegat Inlet, where the lighthouse is located. The Waterway Guide shows two anchorages, one in an enclosed bay west of the light, but only accessible from the north and a second at Conklin Island. I’m not sure which anchorage I’ll use, depending upon how tired I am and which way the wind will be blowing.
...Sedge Island to Barnegat Light |
Detail of Barnegat Inlet Area Along with a Magnetic Azimuth ("81 m") from Conklin Anchorage to the Light |
I do want to explore the Wildlife Refuge, so I print a chart that covers most of the Refuge.
Edwin B. Forsythe National Wildlife Refuge |
Adding 'Compass Azimuths' to a Chart
To do that, I must convert the azimuth reading from the chart to a magnetic reading I'll use on my compass. To get the magnetic azimuth, use the formula:
From the chart, the true azimuth from just northwest of Barnegat Light to the mouth of Forked River is "328°t". Applying these numbers to the formula, m = 328 - (-13) and therefore the magnetic course is 341°m. Disregarding wind and current, if I maintain a heading of 341°m from the tip of the peninsula northwest of the Lighthouse, I'll be at the mouth of Forked River.
But please note, if I use the true azimuth (from reading the chart) on my compass, I'd follow the dotted line (328°m) and end up south of Forked River.
Example of not applying a declination correction |
Tide and Wind Charts
Tide Chart for Barnegat Inlet |
Example of a Windfinder Table |
Other Preparation
Example, using my iPhone Cyclemeter app, I rowed a half mile in 8”35’’’ for a speed of 3.74 mph (a little above average ‘cruising speed’ for me) using 166 strokes, which works out to 15.9 feet per stroke (let’s call it 16 feet per stroke) and a stroke rate of 19 strokes a minute. Of course, how tired I am, wind and current conditions all will affect the outcome, but setting base line numbers (more than just this one base line) for different conditions gives me the ability to estimate distance using just time or number of strokes. We’ll talk more about estimating distance in a later post in this series on piloting.
The ‘speed’ formulas to remember are:
- Distance (in miles/kilometers) equals Speed (in miles/kilometers per hour) multiplied by time (in HOURS)
- D = ST (Think “D STREET”)
- (Divide both sides of the equation by T results in Speed = D/T)
- (Or divide both sides by S results in Time = D/S)
- 60 times Distance (in miles/kilometers) equals Speed (in mileskilometers per hour) multiplied by time (in MINUTES)
- 60D = ST (think “60 D STREET”)
- (Divide both sides of the equation by T results in Speed = 60D/T)
- (Or divide both sides by S results in Time = 60D/S)
Water ‘proof’ the charts you’ve printed out with a clear finish such as Rust-Oleum Clear.
To keep the charts dry, yet available, make a water resistant chart holder.
For example, varnish or paint a plywood base 8½” by 11” (assuming the charts/tables you print are on 8½” by 11” paper). Cut a piece of clear acrylic (Lucite, Plexiglas, etc.) 9” by 11½“. Glue a ¼“ wide piece of self-stick weather stripping around all four sides of the bottom of the acrylic so that the plywood base, and charts, fit inside the weather stripping and up against the acrylic. Hold it all together with spring clips. The weather strip will prevent rain/spray from seeping under the edge of the acrylic (though it will not protect the charts under the acrylic from total immersion).
Chart Case |
The Fine Print
What we’ve discussed here is the basic cruise preparation from a piloting point of view… Preparation of your boat, your fitness, your food and your equipment all must be done in addition to the piloting preparation introduced here.I’m not a professional pilot. I try to be accurate and I check my information, but I’m not perfect. This post is for information purposes and is intended to be only a starting point for learning the skills of piloting. As with any activity with a small boat, there is always the opportunity for ugly surprises. Practice the skills under ideal circumstances and you’ll increase the probability of being able to use the skills during an ugly surprise to keep you and your boat safe.