Tuesday, 6 March 2012

Collecting and displaying GPS tracks

This plot was captured with iNavX on my
iPhone, then emailed to myself, and the
.kml file opened in Google Earth.
If I record a track in iNavX using the background option it seems it will usually keep recording while I do other things, but not always. I'm not sure what switches the recording off, maybe running another app that steals control of the GPS? Once I have a track I can email it to myself as a .kml file and open it in Google Earth. From there the display options would seem to be huge. When emailing a track it also sends it in .gpx format, which should result in a bunch more options. Again, too many choices ;-)

This plot is Google Earth showing a
.kmz file from Navionics on the iPad 
Navionics on the iPad also let me record a track, but it only records while it is the foreground app, which may actually make it more predictable. It draws dotted lines between points while in background. It will also send a track to email as a .kmz file, which can also be opened with Google Earth.

More important perhaps is that Google Earth allows me to load and display both tracks at the same time so I can mix and match. Of course, this means I can't play with the images unless I have net connectivity, but that's probably OK.

X-Traverse provides another way to exchange data between devices and have access to the full chart library purchased through XT on various devices, including iPad, iPhone, Fugawi on PC, etc., although I don't know if it will work with my ancient Fugawi.

Epiphany Moment: My computer doesn't need to know current positions in order to view charts and make plans in great graphical detail and my portable display doesn't need to show great detail in order to provide immediate guidance, as long as the plan can get from the computer to the portable display.

Sunday, 4 March 2012

An Embarrassment of Options

There is such a thing as too much choice in electronic navigation. In the best possible world I would have have a continuous, detailed history of the boats position from launch to haulout, readily accessible on all my various devices, but I could spend an enormous amount of time, money, and electrical power doing that and it's way more than I need for practical navigation and documentation.

For safe operation, I need to be able to:
  • see where I am on a chart and which direction I'm going
  • monitor position at anchor and generate an alarm if it changes too much
For navigational convenience, I want to be able to:
  • know how far I am from my immediate waypoint
  • know how far I am from today's planned destination waypoint
  • ETA is convenient, but I can divide by speed in my head
For fun, I want to be able to:
  • show a pretty map of where I am now
  • with a track of where I went today
  • or a track of where I went this week
  • or a track of where I went this summer
So I am playing with iNavX on my phone and Navionics on the iPad  to see how the "pretty map"part of the charting works out. Navionics will only record a track while it's the active application and fills in a dotted straight line while it's not. iNavX appears to be doing a good job of listening and tracking in background, while sucking down the phone's battery.

A new app for called Drag Queen (really!) seems to provide a pretty comprehensive anchor alarm, with a better UI than my old GPS 76 and an audio alarm siren much more likely to wake me.

New C-Map NT+ charts for the Navman should provide good coverage at the helm in Lakes Huron and Michigan.