Sunday, March 31, 2013

GPS backup and waypoints

My first GPS for was the very basic Geko 101 below. Since getting Little Grace I obtained the Garmin Map 76cx and the Geko was demoted to backup.

Garmin Geko 101
Garmin Map 76cx


However, I did not get round to entering the waypoints we amassed during one (2010) and a half (2012) seasons of sailing. This has left the daunting task of manually entering 92 waypoints into the Geko. Apart from being time consuming there is the concern that one wrong digit could get us up close and personal with the hard stuff. As we will now have an infant on board for one of the two of us to look after a backup GPS to verify where we are in relation to the same waypoints marked on the paper charts and pilotage in the real world is a welcome tick in the box of measures taken for getting us all home safely.
Enter the Etrex 10, it is relatively cheap but basic unit. Maps can't be loaded but that is where I started with the Geko and many boats have basic units to use alongside paper charts as their only GPS, so no problem there. The Etrex 10 does have the advantage that way points, routes and tracks can be uploaded from the computer.

I contacted Garmin help to check the Etrex 10's compatibility with Mapsource, the computer program I use to plot waypoints and plan routes to upload to the Garmin 76. I was told that the Etrex 10 was not compatible with Mapsource but I could upload routes and waypoints from Mapsource to the 76, download them into Garmin's free basic map program, Basecamp, then upload them to the Etrex 10. Apparently this process could be reversed but that is of no interest to me.

I tried it and it worked but if a waypoint occurred in more than one route it was listed the corresponding number of times in the waypoints list. I contacted Garmin again and was told I could get round the problem with another Garmin program, Homeport. For €29 this would interface with both the 76 and the Etrex. I was about to pay the €s when it occurred to me to check that the Etrex 10 is not compatible with Mapsource myself. It turns out that waypoints and routes can be upload to it from Mapsource without any problems. I will have to check a few waypoints to ensure they are where they should be but the coordinates are correct.  
Some readers used to sailing in more open waters may be thinking that 92 waypoints is excessive but with so many islands and rocks there's is always plenty of navigation to do.
The appropriate paper chart is always open on the chart table or in its plastic cover in the cockpit, along with the pilotage plans for the tricky bits.
The GPS is used to verify our position and course to the next waypoint by checking it against the chart and the real world. The waypoints are placed where boat routes change course or significant navigation points. In addition to being numbered I have added the description of what buoyage to look for in the real world. For example, 061 PB = WP 61 Port Buoy.  
A  typical part of one of the electronic charts. Click and then zoom to see the detail.

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