Re: [Talk-ca] Canvec vs. GPS
Being cynical I'd tend to favour CANVEC they tend to have spent more money on their GPS units. Cheerio John On 6 March 2011 20:44, Samuel Dyck samueld...@gmail.com wrote: Hey everyone I am presently preparing a careful import of Canvec data into Mantario area. I have stumbled across a trail that appears to be a GPS track. The problem is that while this trail did not overlap with the old old low detail lake data, it conflicts in some areas with the Canvec data. Which data should I adjust? The overlap between the two ranges for 17cm to 30m. An inspection using Landsat (sadly the best imagery for the region) favours Canvec. I realize that this is a tricky subject. I'm assuming Godwin's law does not apply to this list. Sam Dyck ___ Talk-ca mailing list Talk-ca@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-ca ___ Talk-ca mailing list Talk-ca@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-ca
Re: [Talk-ca] Canvec vs. GPS
On 7 March 2011 01:44, Samuel Dyck samueld...@gmail.com wrote: Hey everyone I am presently preparing a careful import of Canvec data into Mantario area. I have stumbled across a trail that appears to be a GPS track. The problem is that while this trail did not overlap with the old old low detail lake data, it conflicts in some areas with the Canvec data. Which data should I adjust? The overlap between the two ranges for 17cm to 30m. An inspection using Landsat (sadly the best imagery for the region) favours Canvec. I realize that this is a tricky subject. I'm assuming Godwin's law does not apply to this list. Hello, One thing to keep in mind is that GPS tracks are not the ultimate answer to everything. If you want to have reliable data from GPS, you would want to have multiple traces from the same area. A mainstream GPS receiver will have an average precision ranging from 5m to 10m. They can be quite useful though to locate more precisely some features. Also bear in mind that aerial imagery is also not perfect and might not be properly aligned. In the end, I would trust in your case the CANVEC data since it is supported by the imagery, but nothing prevents you at some point to go over with your GPS device to go and take some measurement to check if CANVEC and/or landsat are really accurate. It is a great strength of OSM to be able to import some data and then go and check if it really makes sense on the ground, as it could have changed since the landsat picture was taken. One perfect example is one street in where I used to live which has a roundabout. Only a commercial provider had it right and all aerial imagery that I have seen was not showing it, including the French cadastre. So don't worry too much, import the data if you can and then try to go and check later. Emilie Laffray ___ Talk-ca mailing list Talk-ca@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-ca
Re: [Talk-ca] Canvec vs. GPS
On Sun, Mar 6, 2011 at 6:57 PM, john whelan jwhelan0...@gmail.com wrote: Being cynical I'd tend to favour CANVEC they tend to have spent more money on their GPS units. Based on experience I'd go the exact opposite way as Canvec data can be extremely old and inaccurate. Today I removed a Canvec way describing the Blackmud Creek from the database. Dan Charrois had imported the waterway from Canvec, and the imported way overlapped the existing way. Remnants of that can be seen here for a short while. http://www.openstreetmap.org/?lat=53.4262lon=-113.4888zoom=14layers=M Both renditions can be seen where the creek crosses Ellerslie Road. Hiigher zoom levels have already been rendered. Canvec buildings are horrendous: http://www.openstreetmap.org/?lat=53.42826lon=-113.49479zoom=17layers=M http://www.openstreetmap.org/?lat=53.4145lon=-113.54344zoom=17layers=M http://www.openstreetmap.org/?lat=53.43157lon=-113.54426zoom=17layers=M Feet on the ground are the best judge of accuracy. James VE6SRV ___ Talk-ca mailing list Talk-ca@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-ca
