[Talk-ca] ACQTECH vs. Valdate vs. OSM User imput for CanVec HD

[Calgary Trail Maps]

OK, I'm not sure the big concern.

I've driven that track twice, so the track should be pretty good (see
attached, 2 tracks, different years).  Waterways are not generally that
accurate and yes the creek is at the bend in the track (that bend is the
ford).  The waterway normally comes from the federal Topo maps which were
hand drawn at some point based on aerial photos.  They were never intended
to be GPS accurate and usually do not ever get updated.

John

-----Original Message-----
From: simon at mungewell.org [mailto:simon at mungewell.org] 
Sent: March 12, 2009 9:30 AM
To: Sam Vekemans
Cc: Calgary Area Trail Maps; Simon Wood; Talk-CA OpenStreetMap;
Moreau at mungewell.org; Jean-Sébastien; Dale Atkin; Richard Degelder;
geobc.servicedesk at gov.bc.ca
Subject: Re: ACQTECH vs. Valdate vs. OSM User imput for CanVec HD

> Hi, i have an area, which i found interesting.
> The York Creek (river) ish..

Are you perhaps refering to this spot?
http://www.openstreetmap.org/?lat=49.58793&lon=-114.5186&zoom=17&layers=B000
FTF
http://www.flickr.com/photos/24244464@N03/2777260804/in/set-7215760682069942
4/

Where I sat with my doggie, having lunch on a fine afternoon last summer.

Looking at the sources available to me (OSM, OSM-GPX, CatMP and Canvec), it
appears that the Canvec waterway (coded 1470171) is about 15m too far west.

That said, consumer GPS is not going to be very accurate. Look how the
(only!) GPX track is very noisy here. The only real way is to get multiple
GPS tracks going through the area an visually average/discount them to get
an approximately true location.

One thing that we have on our side when looking at waterways, is that water
is lazy and will take the easy route. So if you look at this area with a
contour layer you might be able to confirm which of the waterways is in the
wrong place.

Cheers,
Simon.
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