search

vicb / VisuGps3

Display GPS tracks on top of Google maps
MIT License
36 stars 13 forks source link

Add an option for displaying the track enveloppe #10

Open JFLarvoire opened 8 years ago

JFLarvoire commented 8 years ago

For track shapes that are very different from a triangle, I'd like to know what's the geometric enveloppe of my track. (The enveloppe is like a giant rubber band wrapped around the track.) Would it be possible to add an option for displaying the enveloppe and its length? For example, a small button with a lasso in it, below the other green buttons in the top-right corner of the map, would show/hide the enveloppe on the map, and a message box somewhere with the enveloppe length and its opening lengths. (The opening length is the distance between the start and end waypoints.)

vicb commented 8 years ago

Not sure what you exactly mean ? Do you have an exemple / known OSS implementation ?

JFLarvoire commented 8 years ago

Here's an example of a flight track, where I manually added the enveloppe in green. enveloppe de jfl

vicb commented 8 years ago

What is the purpose ?

JFLarvoire commented 8 years ago

The purpose is to get an evaluation of the track length that is more realistic than with the standard geometric shapes now used for distance scoring. With a fixed number of sides (3 for FAI triangles, or even 4 as were allowed in the past by French CFD rules), many "interesting" tracks (those with many extrema, or with convex shapes like a circle) do get widely under-evaluated. The example image above shows that well on such a track, with the green enveloppe much longer than the blue FAI triangle. On the other hand, tracks with just 3 points will often have an enveloppe almost identical to their FAI triangle. This is the case for most of the top tracks in the CFD this year.

I proposed that idea publicly last spring in a letter that was published in the #166 issue of Parapente Mag. Then last week, I was happily surprised to learn that a Paramotor association had adopted it and implemented it for their own distance scoring. See their new rule here: [http://cfdm.forumperso.com/t141-reglement-de-la-cfdm] And here's an example of a paramotor track with the enveloppe shown. [http://cfdm.forumperso.com/t130-0001-13-08-16-julien-heyl-79-6-km-homologue]

So now my request is to add that capability to VisuGps as an optional feature. People who don't care will see no change. And people interested can visualize their envelopes, and get its length, by clicking on a button.

Note that I've heard that many graphic libraries do already have functions for drawing envelopes. If you do use such a library, this may be relatively easy to implement. Else it'll be more work. I'm a developer, so I volunteer to contribute if needed.

vicb commented 8 years ago

Looking at your ex your previous reasoning does not seem valid.

If the question is how to better reflect "real" distance for recreational pilots, may be there are better options ? (ie more segments).

I'll probably be quite busy for the 2 coming weeks but nappy to discuss this after.