Post by: wayne on February 20, 2007, 07:53:53 AM
Many GPS's have a large track log, and smaller saved logs. Ex: Garmin 76CS has a 10,000 point active log, but a 500 point saved log. The GPS reduces the track size (with no user control) on save. DeLorme's PN-20 lets you save full 10k unreduced track logs, but they take up a lot of memory with too much data. (Yes, I can expand from a 2G to 4G card, but that's not my point, or the solution to every problem).
You seem to have some sort of a "reduce" function with the networks, but I'm suspecting (after playing with it) that it just reduces points based on overlapped routes, not a true "reduction" forumla. I would like the ability of the tool expanded. I'd like a way to better manage / average tracks. Examples:
• Track Reduction. Active track logs can be reduced by using the reduction tool, little by little. But the Garmin GPS (and others) have a saved-log limit of 500 points per saved log. Allow me to say I want it reduced to "X" number of points, and TopoFusion will reduce the full tracklog from it's current size to 500 points via an intelligent mathematical function. I know you have some of that already, but some suggestion are:
- When I travel in a straight line, you could eliminate most in-between points until there's movement in the perpendicular direction.
- When I stop and sit for a few minutes, I wind up with dozens of points that describe the same location. These could be reduced/eliminated.
- No two points withing "x" distance" of each other, even on turns. (When I import my 10k Garmin track log, it seems to make extremely descriptive low-speed turns, even while making less accurate descriptions on higher speed tighter turns).
• Allow me to remove "x" number of points. While the Garmin default method set on "Very High" logging produces many points, the DeLorme track logs (Street Atlas/Topo/PN-20 GPS) have many, many times more detail (and often too much detail, but I don't want to keep stoping and changing the logging method....and you can't change the logging method when you're 4x4ing with the laptop software version of the program). This grows very large files. As a starter, I might remove every 1 of 2 points, or every 2 of 3 points, before I apply other advanced reduction methods.
Post by: Krein on February 20, 2007, 10:54:48 AM
This functionality is already in TopoFusion, albeit not in an obvious place!
Right click on any track in the map and choose "Simplify/Spline". You can set the slider or enter the number of points you wish to simplify the track to. Splining is a little different, you may want to check the docs on how it works, but basically it *adds* points to the tracks.
The simplify algorithm is well tested and close to optimal for the sitatuations you describe. Give it try.
What is missing is a way to split and simplify a track for upload to saved tracks. Garmins, for example, have twenty 500 point tracks that can be used. Often you want the most detailed track available, so you really want to take a 10,000 point track and split it into chunks of 500 points. I have code to do this (since I often need it myself) but no user interface, so only I can use it.
But I plan to make it available to everyone.
Post by: wayne on February 20, 2007, 02:55:29 PM
I'd also suggest you include the tool in the Analysis section (with network) then maybe have a "click to select track" arrow pop up. I'm trying to think of a way to make it more obvious. Maybe a "tools" section with Network, Simplify, and Playback.
One thing I noted was that where I sat around a gate a little bit (averaging waypoints with one GPS) and have many points in one spot (from the 10k points GPS), TopoFusion reduced the number of points but didn't 'sense' was was hovering in one spot and completely eliminate them. That was reduced with the Trail Network tool, however.
For your 10k limit, could you upload your points to the active memory instead of a shared slot? If you were using the "wrap" function, your new track would wipe out your old track by the end of the trip. Or you could simplify to 7500 points and upload to the active track memory, then use the first 2500 for your new track.
I also have a software friend; he wrote his own email client and is the king of very neat software that is only useable by him since he did it.
Splining might have been an issue in the past, but now that i have a GPS that stores 10k track logs, I will most likely only be reducing information.
On a side note, I have googled John Krein and received either trail information, or the obit of a guy in Canada. I noticed you also use his name as your admin account. Can you point me to a link to learn more?
Side note 2: I live just south of Ajo/Kinney. On the rare occasions I leave work by 5, I hit the park (and have sent you some trail updates; I'll fill out the east end sooner or later and get it to you). My question is, how do I get a job like yours so I can get on the trail all the time!
Side note 3: Though I only use the network property (I use a competing product for map needs that comes with maps and allows me to add a notes layer), and now the reduction property, I'm getting closer to sending you money anyway. I've now found another reason to use this product.
Post by: Krein on February 20, 2007, 07:41:25 PM
Quote from: wayne,Feb. 20 2007,2:55
| Quote |
| One thing I noted was that where I sat around a gate a little bit (averaging waypoints with one GPS) and have many points in one spot (from the 10k points GPS), TopoFusion reduced the number of points but didn't 'sense' was was hovering in one spot and completely eliminate them. That was reduced with the Trail Network tool, however. |
Yep, you're right, simplifying doesn't try to eliminate "standstill" gps points.
| Quote |
For your 10k limit, could you upload your points to the active memory instead of a shared slot? If you were using the "wrap" function, your new track would wipe out your old track by the end of the trip. Or you could simplify to 7500 points and upload to the active track memory, then use the first 2500 for your new track. |
Genius! I can't believe I didn't think of that before...
For my longer trips (e.g. riding the entire Arizona Trail), 10,000 points is really not enough. But I should at least be able to use part of the active log to store some points.
Using all 10,000 may be risky. If you're tracking, and get off your route too much you may start overwriting exactly the data you need (what's just in front of you!).
| Quote |
Splining might have been an issue in the past, but now that i have a GPS that stores 10k track logs, I will most likely only be reducing information. |
Splining is interesting sometimes because it better approximates the actual path you took with the GPS. This can sometimes add distance/climbing to a track. But it's not a commonly used feature of TopoFusion. I actually wrote the code for a semester project in a math class.
| Quote |
On a side note, I have googled John Krein and received either trail information, or the obit of a guy in Canada. I noticed you also use his name as your admin account. Can you point me to a link to learn more? |
It's a mystery...
... actually I just really like the trail with his name. I have also tried to find more info about it, but I think he's just a guy that lives in Tucson and possibly built the trail.
| Quote |
Side note 2: I live just south of Ajo/Kinney. On the rare occasions I leave work by 5, I hit the park (and have sent you some trail updates; I'll fill out the east end sooner or later and get it to you). My question is, how do I get a job like yours so I can get on the trail all the time! |
Simple: accept a lower standard of living.
Then you have plenty of free time. TopoFusion doesn't make what most people would call a decent living. But I'm still used to the student lifestyle and I have time to go on huge bike trips, i.e. enjoy my life.
Post by: wayne on February 27, 2007, 03:02:59 PM
• It makes sense to right-click because you perform the operation to one track at a time. However, you might make a tools menu and include just the tools (like track network), including a menu item for Reduction. Reduction could have a pop-up box saying "select track (or right click on a track at any time)" Not an elegant solution, but a little more obvious for new users and would point them to the easier selection. I don't care so much now that I know where it is.
• The reduction worked great. I experimented with dividing DeLorme GPL logs by 10 to 3. I settled on divide by 5 for offroad 4x4 use. This reduced tracks to 20% of their original size, while maintaining near perfect mapping data at high zoom.
Offroad 4x4
- Div by 9 decent for general use where memory is scarce.
- Div by 7 very good for curved roads, very good at zooms up to 15.
- Div by 5 virtually indistinguishable at zoom 15, great even on switchbacks. Very good even at zoom 16 and 17 (max).
When combined with the Average/Network tool to average out where I went the same place twice, your outstanding tools reduced track sizes to about 10-15% of original size (depending on how many times I backtracked), with no loss in quality.
This lets me store more locations on my GPS, and speeds up 3D rendering on my computer.
Great job, and thanks for the help.