Re: [Gpsbabel-misc] using the discard filter

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

> i wonder about the discard filter,
> are there any limitations to this filter,
> e.g. that it depends on HDOP and VDOP data
> not stored by all GPS's?

It does rely on the DOP data.   Most common GPS receivers (the
kind with screens and keypads) do not record this data and instead =

do their own such filtering.   This filter is useful mostly to the
data logger class of products that just scribbles NMEA sentences
every second or two without any actual processing of that data.


> my challenge is that sometimes i notice data points
> that are completely off, probably due to lack of satellite
> fix, typically after starting the GPS or covering the unit,
> or standing close to a precipice (or between two) or at the
> bottom of a canyon.

We've discussed adding "smoothing" filters in the past, but I
can't recall that any programmer types have actually tackled
it.

> when using the radius filter, is it possible to have
> gpsbabel draw the circle into the output, e.g. KML?
> this is of course outside the scope of gpsbabel,
> but might be useful for debugging and documenting
> results of the filtering command.

It's not the kind of thing we've done, but it's an interesting
idea.   The various filters could create a little stack of records
showing what they did and certain output modules could look in =

those for an audit trail and introduce additional markup showing
what we did.   It would probably be hard to describe well internally
without blurring the dividing lines between filters and output modules
that we've tried to keep pretty strong.

I'll put that on my mental list of midnight projects to tackle.