Merge with other data
Posted: Mon Jul 16, 2012 9:52 pm
I've started using the iBike software feature that lets me merge with, in my case, a Garmin TCX trace of my ride to get Lat and Lon.
I've found a couple of problems with this:
When I use the Garmin timestamps the output often had them a bit jumbled, some timestamps are reused and out of order.
Most of the time the only thing needed to synchronise the two sets of data is to do a small timeshift so it would be good if the merge feature allowed that, maybe even as a manual operation (i.e. type in an offset). Basically I've taken to doing just that by loading the iBike file and the TCX into a spreadsheet and graph speed against time then fiddle with the time difference till they align. Having done that I now have an accurate time difference between them (which happens to be 20 seconds). I also calculate the least squares fit so I know if I'm dialled in right.
Another problem is that whilst iBike does a reasonable interpolation of Lat and Long it only goes to 5 decimal places whereas the Garmin does 6. At least that's how it comes out on the CSV export. So the interpolation tends to appear as a series of "steps" instead of a smooth line. This affects my current pet project where I graph Abs Wind speed against heading to see if I've got the iBike positioned in reasonably "clean air" setup. Just an experiment but having the route moving along at right angles messes up the graph.
I've also tried using GPS Babel to do the interpolation on the TCX file which is better but it has other issues.
So to summarise a couple of features:
1) Allow a simple time offset to merge iBike files with other data
2) Use 6 decimal places on the Lat and Long interpolation (if that's not already happening) and output same to the CSV file
I've found a couple of problems with this:
When I use the Garmin timestamps the output often had them a bit jumbled, some timestamps are reused and out of order.
Most of the time the only thing needed to synchronise the two sets of data is to do a small timeshift so it would be good if the merge feature allowed that, maybe even as a manual operation (i.e. type in an offset). Basically I've taken to doing just that by loading the iBike file and the TCX into a spreadsheet and graph speed against time then fiddle with the time difference till they align. Having done that I now have an accurate time difference between them (which happens to be 20 seconds). I also calculate the least squares fit so I know if I'm dialled in right.
Another problem is that whilst iBike does a reasonable interpolation of Lat and Long it only goes to 5 decimal places whereas the Garmin does 6. At least that's how it comes out on the CSV export. So the interpolation tends to appear as a series of "steps" instead of a smooth line. This affects my current pet project where I graph Abs Wind speed against heading to see if I've got the iBike positioned in reasonably "clean air" setup. Just an experiment but having the route moving along at right angles messes up the graph.
I've also tried using GPS Babel to do the interpolation on the TCX file which is better but it has other issues.
So to summarise a couple of features:
1) Allow a simple time offset to merge iBike files with other data
2) Use 6 decimal places on the Lat and Long interpolation (if that's not already happening) and output same to the CSV file