Confusion concerning Climbing Analysis

[bobmaloney@compuserve.com]

I have some questions concerning the Climbing Analysis routine.

First, if the Presets is set to Straight Dem, what are the differences between the various DEM sources:
    -Use local Dem files, if available
    -Download/cache
    -Download/cache, force SRTM ?

I get significant differences in elevation gain depending on which source I choose. Is there a recommended choice?

Second, I understand that the first 3 selections of DEM interpolation methods are different mathematical interpolation techniques. However, what does the 4th technique, "From loaded tracks", imply?

Thanks for a great product,


                                                             BobM

 

[ScottMorris]

Hi Bob,

The recommended choice is "Download/cache" as long as you aren't interested in an area that is near any US border.  There are two elevation datasets available from the server.  One is 30m NED data for the whole US, and another is SRTM 90m data for the rest of the world.

TF automatically chooses between the two, but if you had a track that crosses the US border you'd need to force it to only us SRTM.

The other option, Local Dem files, is only pertinent if you have downloaded and set up your own DEM files.  For most people this won't apply, but some users do have their own DEM collections (this is separate from the now 'local' DEM files that TF automatically caches for you).

"From loaded tracks" was supposed to be removed!  It was removed from 3D options, but apparently not climbing analysis.  Thanks for pointing it out.  It was a very early attempt to create elevation data by interpolating GPS collected elevations.  An interesting experiment and perhaps useful before TF had the elevation download/caching system.

Thanks for the questions.

[bobmaloney@compuserve.com]

Thanks for the quick reply which leads to several more questions.

 First, is the preset TOPO USA the Delorme system or the National Geographic system?

  Next, what is the preset Training Center ? What are its characteristics?

  Third, what does the BOX FILTER WIDTH do?


                            BobM

[ScottMorris]

1. Topo USA.
2. Training center primarily uses the Box Filter to remove noise from the calculation.
3. It controls how much smoothing of the signal (elevations) is performed.  The wider the filter, the more smaller total climbing should be.

All of the 'presets' for different software are simply approximations / best guesses for what the programs are do.  I don't actually know what they are doing.