[Cdt-l] accurate GPX track based on the new mapbook data?

Scott Parks public at postholer.com
Sun Mar 27 19:14:34 CDT 2011


First, here are 3000+ way points viewable in google maps. These include 
Dan's, journalists, SPOT users, and others who have contributed their 
data. This is a shot-gun blast of way points. The trail trace is a 
hybrid of various sources and does not necessarily reflect the official 
route. Warning, this CDT google map showing waypoints may kill your 
browser, be patient, works great in FireFox 4 and IE9:

http://postholer.com/gmap/gmap.php?trail_id=2&zoom=5&dist=0&markertype=14&vw=0

Thoughts on trail traces and maps. Imagine looking at a 7.5 minute map 
(1:24K). Imagine the trail trace drawn on the map. The colored line 
(trail trace) is going to be a least 20 feet wide, and more like 30. 
Assuming accurate data, having a lat/lon point more frequently than 20 
feet gains nothing in map quality as it wouldn't be displayed. If I had 
hourly accurate tracks with 10K data points I'd grab only points that 
were 20 feet apart and toss the rest. That's 264 points per mile. Much 
more manageable without sacrificing quality. From a 1:24K map 
perspective, 50 points per mile is quite fine.

The GPX data format is just that, a format. It speaks nothing of data 
quality. The GPX format will hold accurate and inaccurate data equally 
well. It will also hold professional and recreational data equally well! ;)

I've been dragging my feet about making some 1:100K and 1:250K overview 
maps available for the CDT. If anyone has a need for these, let me know. 
I could use the motivation.

-postholer

-- 
www.postholer.com



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