sanitizing cardio trainer tracks for sharing?

I have some cardio training tracks; I want to publish them,
but with all the points within about 200 meters of my house
elided for privacy.

I put together this Makefile stanza:

---8<---
HOME_LAT=30.1234
HOME_LON=-90.1234
NEIGHBORHOOD_RADIUS=200M
cardio_20apr_pub.gpx: CardioTrainer_Apr-20-2009_03-20PM.gpx
	$(GPSBABEL) -i gpx -f $< \
		-x radius,distance=$(NEIGHBORHOOD_RADIUS),lat=$(HOME_LAT),lon=
$(HOME_LON),exclude \
		-o gpx -F $@

---8<---

(The actual LAT/LON that I'm using are different; I'd rather
not include them in this message to www-archive.)

And this converts it from gpx format to KML format:
---8<---
.gpx.kml:
	$(GPSBABEL) -i gpx -o kml $< $@
cardio_20apr_pub.kml: cardio_20apr_pub.gpx

---8<---

But when I look at the resulting .kml in Google Earth,
all the points are there, even the ones within 200 M of
my house.

Clues? help?


-- 
Dan Connolly, W3C http://www.w3.org/People/Connolly/
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