Track Point Reduction

[wayne]

Right now, you right click on a track and you can reduce it.  I love the function as it lets me take detailed measurements in the field (every 10 feet) then get a great representation after reduction, and it's much smaller when pushing back into a limited memory GPS.

In general, this is what I've found for 4x4 use:
Div by 9 (11.1% of original) decent for general use.  Use when memory is at a premium.      
Div by 7 (14.3% of original) good on curvy roads, overall pretty good representation for zoom 15.      
Div by 5 (20.0% of original) virtually indistinguishable from original tracks at zoom 15, great even on switchbacks.  Very good even at zoom 16 and 17.      

My suggestions are:
- Right now I use a spreadsheet for the math.  I have to right click the track, see how many points, do the division, and then type the answer in and have TF reduce the track.  Have a universal "divide by" operator so I don't have to do this.  I can default it to "5" or "9" (the program will remember this) and the track suggested size will be 1/5 of the original.

- Allow me to use an arrow to select a group of tracks (or if it's easier, just apply to all tracks) and let me reduce all selected tracks at once.

- Put it up on the Analysis toolbar and let me reduce all tracks in the open GPX document at once, without having to select a single or group of tracks.

[Krein]

Wayne,

That's funny, I've only ever wanted to reduce tracks to a certain number -- never thought about dividing them by a certain amount.

We sure could add that calculation to the dialog.

I am 100% with you on a way to select multiple tracks, even if only from within one file.

I envision a new dialog, in analysis, for these tasks, perhaps leaving the current one as is for single track operations.  One thing I've been meaning to add for some time is the ability to simplify and split a track for upload to a Garmin unit's 'saved tracks' memory area.  I have code to do this in the program, but it's only accessible to me so far.  This would be a good place to have that function as well.

E.G. you have a 20,000 point track and want it simplified to 10,000 and split into twenty 500 point tracks.

I hope to start working on this soon.  Thanks.

[wayne]

Although it's probably clear from the above, my track lengths are wildly different in size, which is why I like the percentage.

Reducing a 10,000 point track to 500 points is not the same as reducing a 750 point file to 500 points.

Thanks for looking into it / adding in the future.

[wayne]

As an FYI, this is reduction function.  This is what I do when logging is set to high resolution while gathering track points.  High resolution to me means:
- point every 10 feet
- point every 2 seconds
I run the reduction after I average the tracks.  (and usually after I re-join tracks that form a line end-to-end)

Offroad 4x4 driving.  Take original track and….  (% of original track points)
• Div by 9 (11%) decent for general use.  Use when memory is at a premium or you don't need a perfect map.
• Div by 7 (14%) good on curvy mountain roads, overall pretty good representation for high zoom (Zoom 15 in DeLorme Topo)
• Div by 5 (20%) virtually indistinguishable from original tracks at zoom 15, during 'regular' dirt roads.  Is great on switchbacks.  When going to zoom 16 and 17, it's still very good.

Mountain Biking / Hiking  (% of original track points)
If there aren't a lot of side trails (low trail density) you can obviously use the greater reductions above.  If there are a lot of trails, you probably want greater resolution so you can more quickly figure out if you took the correct fork in the trail.
• Div by 3 (33%) and it's nearly indistinguishable from the original even at the highest zooms.
• Divide by 2 (50%) and it's near perfect to the GPL.  This gives one point about every 20 feet but intelligently reduced to give more points on curves, less on straights.  I would question even using this resolution, however, although it does cut track sizes in half.  This is the "compulsive-attentive" level of logging (unless you count not reducing track sizes at all).

As a reference, I was in the Blue Spring/Cape Solitude area of the Grand Canyon.  I had the "in" track and the "out" track, along with some other tracks from exploring and turning the GPS on and off.

I started with DeLorme track logs  >> Saved to GPX.  (Saves point every 2 seconds, even when not moving)

Opened GPX in TopoFusion and used the Network function to automatically:
- Average tracks where I drove the same road twice.
- Remove stubs where I pulled down a road/trail for a second then got back on.
- Doing this reduced the GPX file from 1.3 meg to 1.1 meg and made multiple-track roads more accurate.

I then used the reduction function where you can specify how many final points to have.  Since it was for off-road driving use, but not in an area with much confusion over rods, I used "Divide By 7"

Final file size was 232k and was virtually identical to the 1.3 meg original.  Unfortunately, I didn't note the starting and ending number of track log points.