GPS navigation for kayak fishing

Author: Holger

Category: Safety & navigation

Published on Saturday, 05 December 2009 11:36

Written by Holger

The Global Positioning System (GPS) is one little electronic device that has gained a lot more popularity over the past few years. So much so that nowadays many couldn't imagine going anywhere without one. And what a practical and little useful device it is! Among other things it can tell us where our favourite fishing spots are and help us find that secret reef, shows us where and how fast we're paddling or drifting. When day turns to night or when the weather turns nasty it can guide us back to the ramp. It can even tell us the moon phases and best predicted fishing times! Yes... I am talking about the not so humble GPS.

The GPS is a satellite based navigation system, developed by the United States Department of Defence that can now be used freely by civilians for navigation purposes. Since becoming fully functional in 1993 the GPS has been used for various tasks including navigation, surveying and map-making as well as numerous hobbies... such as kayak fishing! The GPS consists of 24 Satellites on 6 orbits that send out a signal to allow the GPS receiver to calculate it´s precise position (down to a couple of meters), course, speed, as well as show your trip kilometres & duration, record your track, or find the way back for you.

The satellite signal consists of a satellite ID, an almanac, and the (very, very) precise time. Because the receiver knows where the satellites are it can calculate the runtime of the signal and via that the distance to the satellite. With the help of at least 4 signals and a process called trilateration the receiver calculates it's position in 3D.

There are two sorts of GPS, the 'Hand-held' displays the position in the form of coordinates (latitude/longitude) on it´s little screen, and relies on you to transfer it onto a map/Marine chart. The 'chart plotter' shows the position on a map on the built in screen (as well as Lat/Long). There are also combo units with combined GPS/sounder available. Prices start around $150 and raise to several thousand. Most units are waterproof and the Handhelds are generally shock and dust proof too.


In terms of differences in display there are 2 choices: black & white or colour screen. Black & white screens are easier to read in direct sunlight, cheaper and consume less power (which helps battery runtime). But a high resolution colour screen with a built in map is in a league by it's own. Resolution, clarity and readability of  the new screens are simply stunning.

How do I use a GPS? On a typical day I would first save the position of the ramp/starting point on the beach before I head out. That way I can always find my way back, even when the weather and or visibility turns bad. While I'm out I'd track my every movement and mark reefs and points where I catch or see many and or good fish. Over time through sticking to this habit a very interesting map of fishy spots and reefs has formed. The next time I head out I can find my way straight to one of these spots again by simply pressing a button and following the arrow. I can position the kayak and monitor that the drift goes straight over the chosen spot - too easy! It's also easily possible to pre-program well-known fish-holding waypoints into the unit before heading out - all you need is the correct coordinates and the GPS will take you straight there. With the help of navigation software I can read a lot more information out, like trip duration, distance covered, speed at any given moment and display it all on the computer, as well as archive it.

How can I transfer a waypoint from my GPS into a Chart/ map, or read the coordinates of a waypoint out of a map? Obviously you need a chart / Map with a grid printed on, which shows the Latitudes and Longitudes. A calculator, led pencil and ruler are also required. How was that again with the latitudes and longitudes? Which was which?

Longitudes (also called Meridians) run from pole to pole and are divided in 180 easterly and 180 westerly longitudes. The longitude 0 (also called the prime Meridian), runs through Greenwich in London/ UK. Longitudes have always the same length.

Latitudes (also called Parallels) are the ones running horizontal around the world, with the Equator in the middle as prime Latitude. They are divided in 90 northerly (up) and 90 southerly (down) Latitudes and get shorter towards the poles.

The distance between each latitude or longitudes is called one degree. Each degree equals 60 minutes. A minute equals 1.852 km = 1 Nautical mile. (Equator is 40000km : 360 = 1 Degree; 1Degree :60 = 1 minute = 1.852km)

M =Minutes
S = Distance between the full degrees = 60 minutes
A= Distance from the smaller degree to the waypoint.

Transfer a waypoint into a map:   S(mm) : 60 x M = A(mm)


Find the full latitude / longitudes on the map. Now you know the square in which the waypoint must be. To pinpoint the exact spot you'll need to use the minutes.

Measure the distanced between the latitude ( I use mm), and divide the result by 60 to get the length of 1 minute ( in mm). Then multiple it with the (latitude)minutes of our coordinate we want to transfer, to get the distance between the smaller latitude  and the WP ( in mm). Draw a line. Then we do the same process for the longitude, where the lines cross is the waypoint.

Reading a waypoint out of a map:  60 : S(mm) x A = M (minutes)

Divide 60 by the distanced between the full latitudes ( mm), and multiple that with the distance between the smaller latitude and the waypoint (mm), to get the minutes. A good way to practice with your GPS, and learn how to use it before you head out is Geocaching. And it's (family) fun too!! 

All in all GPS is a very useful, affordable and precise form of navigation. It´s a ripper in the bag of navigation tools and sometimes addictive too! But because GPS is an electronic device which can fail or run out of power (carry spare batteries) it can never fully replace good old-fashioned navigation with chart and compass (which I highly recommend learning to use if you don't already know) but should be seen as a very good addition to it.

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