MacSailing.net

I was having a chat with a friend of mine who skippers racing yachts, and we came up with what I think would be a great feature for GPSNavX / MacENC.

Already, you can record telemetry from the GPS and instruments to store a track of your progress as you sail or motor, but all you can do is export it, or view it as a line on the chart. What would be seriously awesome is if you could replay that track with your boat position in relative time. In other words, at the end of a sail, you could play back the entire voyage at, say 3x speed, and what your yacht zip along a track.// pretty cool.

OK.. now, imagine that you're sailing, you could import a "track" that you've created or a route, with speed data and play that back at 1x speed while plotting your real course on the chart. This would enable you to:

1. See a "ghost ship" of where you were on a previously voyage, vs where you are now, comparing how effectively you're sailing against a previous journey (great for racers)

2. Upload a passage plan that takes into account tidal flows and track your progress against that.

I've talked in previous posts about GPSActionReplay, a Java application that allows you to replay GPS tracks (in GPX format) saved from your instruments. However it's not particularly intuitive, and does require tweaking to get maps set up etc..

Just a thought.... anyone else find this useful?

A basic replay function should be pretty easy to implement.

Personally, I'm not sure how how useful it is to compare actual against planned or actual against last time--there are so many things that can make you faster, or in my case slower, than you expect. But the basic idea is definitely interesting, particularly for those of us who like to yarn about what happened / might have happened. For instance you could upload tracks from two or more boats and replay their race. Skippers would no doubt be heard saying things like: "Ah yes, that's where we tacked like a cow in a bog at Mark 7. If it wan't for that we'd have been 29th...". Taking it one step further, you could create a sort of illustrated story by linking in photographs taken at the time, synchronised using GPSPhotoLinker.

Endless possibilities...

I like the photo idea... you could even implement integration with iWeb, so that you can automatically publish your track, with comments and photos to the web.

Then, link it up with Speech Recognition, and... move over Captain Kirk!!!

GPSNavX and MacENC do allow you to step through your recorded track. Enable the track to be displayed with the "Show" menu item on the "Track" menu. Select any track record in the Track window and then use the arrow key to scroll through the list. If you have a chart open with the track position you will see a gray ghost position icon move along as you arrow key down or up in the track history. While not a "play" button it does allow one to replay their days sailing at a speed much greater than real-time.

One can also [command] [click] anywhere along the track plot on the chart and that will select the closest track record in the Track window.

This is very closely related to my own recent feature request. I hoped to see a function added to the track window to allow the track line to be automatically saved as a text file at user-defined intervals. That saved track file could then be imported back into a separate track record window, so that the current track remains visible and capture continues while the old track is also visible. I want to save the track periodically and reset the track window so that the current track window doesn't end up with hundreds of thousands of lines as I record continuously.

Having the old track files available separately opens a world of possibilities. In my case, there is no race, but we keep driving over the same grounds. I want to be able to write notes into the notes field of the old and current track windows. This gives some data keeping functionality like a georeferenced logbook, but if the notes were made visible on the screen you could do all kinds of things. For example, you have a tricky entrance to a remote bay that hasn't been properly charted (common in Alaska) so you follow another boat in the first time, and as you capture the track you write notes into the track record window. After saving the track to a text file, you could import it the next time you visit the area, see how your current progress compares to the known safe track, and read the notes attached to the track. I think it would be very cool to see those attached notes on the screen beside their points.

Some of this functionality already exists. As noted above, you can run down your track by scrolling the track window. You can keep your track window open without automatically capturing points, and click the "New" button to manually enter points of interest and then write a note for the position. I think this is as close as MacENC comes to having an event mark button. Of course you can always double click and make a waypoint name as a note at any position, but that isn't quite the same as showing a separate history file on the screen.

For anyone interested in making notes along their track records, this ability has been recently improved in MacENC in response to my request. There had been a problem with the notes field staying selected while a USB GPS was attached. Text can now be entered as track capture continues. When exporting the track records to a text file the default file name is now the current date. That helps me keep each day's notes separated without thinking too much about naming. I also learned to my pleasure that if I want to write a note in the saved text file the notes field is the last thing on each line. You don't need to carefully put your cursor between the correct pair of commas. Just type your note at the end of the line. The text file field order differs from that of the current track window. If this doesn't make sense to you, just look at a track window and a saved text file side by side. I haven't been recording instruments and there is a series of commas in the text file. The active track window would lead you to believe that you must add text file notes somewhere in the middle of that line of commas.

ReeferJon Wrote:What would be seriously awesome is if you could replay that track with your boat position in relative time. In other words, at the end of a sail, you could play back the entire voyage at, say 3x speed, and what your yacht zip along a track.// pretty cool.

OK, I'm going to add to your request (to make it seriously awesomer). What if you could have multiple concurrent tracks, that you could play back in scaled time? Imaging taking all the track data from each boat's gps after a race, loading them all in GPSNavX/MacENC, then recreating the race in 3x time on the clubhouse TV screen?

What's that you say, you didn't foul me? Let's re-watch the race in MacENC.

Oops, just realized that I basically restated what jfewtr said. Guess I should have read the thread instead of just scanning it before posting :oops: