Re: [Gpsbabel-misc] BBOX calculation

[Robert L. <rob...@gp...>]

On Tue, Jun 1, 2010 at 1:47 PM, John Robert Peterson <jr...@gm...>wrote:

> Does anyone here know the best way to find the BBox of a file? (max/min lat
> long AND time)
>
> I have implemented somthing that uses the simplify filter to bring the file
> down to 2 points, then uses a custom stylesheet to output the times. I then
> export the original file as GPX, and pull out the bbox from the header using
> (if i recall) grep. (this was 2 completly separate implementations that i
> pulled together later)
>
> The result: I have to go and make a cofee while it's working, and at the
> end of the day it's a complete mess.
>

We compute bboxes for the formats that need it.   See waypt_add_to_bounds()
and friends in waypt.c for the details.   The computations should certainly
not take you from coffee time to the end fo the day.   I've experiemented
with files containing millions of waypoints.  Somewhat predictably, virtual
memory becomes the limiting factor.   If you have test cases that produces
that kind of performance for any reasonable data set on any kind of
reasonable computer (please don't submit test cases of a million trackpoints
andn complain that it's slow on a nokia 770) please submit for profiling and
study.


I've never heard of the concept of a bounding box containing time.  It would
be trivial to add to that function if needed and useful.

RJL