[Talk-ca] Intro and a question

Bégin, Daniel Daniel.Begin at RNCan-NRCan.gc.ca
Thu Mar 1 19:19:38 GMT 2012


Bonjour Steve and Bernie,

Agreed with Bernie, I'll go a bit deeper in what has already been said...

NRCan highway=(vehicle) were obtained using GPS (better than 5 meters 90%)
NRCan highway=footway have been obtained from aerial photography (30 meters 90%) and are usually more that 30 years old.

Standard GPS device will usually give an accuracy better than 10 meter 90% in good conditions (no obstacles - mountains, buildings, trees)

It would not be unusual to get a GPS track off by quite a few meters in forest/mountain area. Imagery can also be affected by distortion in such areas - if no appropriate corrections were done. 

However, if you have many GPS tracks that seem glued together, take yours !-)

Best regards,
Daniel


-----Original Message-----
From: Connors, Bernie (SNB) [mailto:Bernie.Connors at snb.ca] 
Sent: March 1, 2012 14:04
To: 'Steve Roy'; Talk-CA OpenStreetMap
Subject: Re: [Talk-ca] Intro and a question

Steve,

	I have had a look at your GPS trace and the OSM data in the Lac Le Jeune area with the Potlatch 2 editor.  It appears to me that your GPS trace matches quite well with the Bing imagery in the area.  Since you are familiar with the area you could accomplish more by simply digitizing from the Bing imagery and supplementing with GPS traces when necessary.  I would trust your GPS trace to be more accurate than the CanVec data in the area.  It is really up to you to decide if you want to reposition existing data or delete it and digitize new features.  I find that sometimes the CanVec data has many nodes and it is time consuming to reposition each node.  The CanVec data is using the tag "highway = footway" where it appears that it is suitable for vehicles.  I suggest "highway = track" is more appropriate.  It looks like another user has already digitized some "highway = track" in this area and created some duplicate ways such as this one:

http://www.openstreetmap.org/user/SRW/traces/1187039

	With your local knowledge it should be easy to identify these duplicate ways and remove the less accurate data.

Bernie.
--
Bernie Connors
New Maryland, NB
bernie.connors at unb.ca

-----Original Message-----
From: Steve Roy [mailto:steve at ssni.ca]
Sent: Thursday, 2012-03-01 14:14
To: Talk-CA OpenStreetMap
Subject: [Talk-ca] Intro and a question


Hi

I thought I'd introduce myself and also ask a couple of questions. I 
live in New Westminster BC and spend a lot of time in the Lac Le Jeune 
area as we have a family cabin there.

I want to start adding data in the Lac Le Jeune area that I collect with 
my GPS when out hiking, biking, 4x4ing, sledding etc. There are numerous 
trails and roads in the area that aren't on OSM.

I have managed to add a couple of forestry roads so far but want to know 
the best way to combine my edits with current roads and tracks on the 
map.There are parts of existing roads and tracks shown on the map and 
they are from NRCan-CanVec-7.0.Some match with my GPS track, others are 
off by quite a few meters.

Should I:

-Leave the existing NRCandata as is and add my data (i.e. my track lays 
over the NRCan track)

-Combine the two and move the nodes of the NRCan?

-Or leave the existing NRCan track as-is and join bits of my track to 
nodes on the NRCan data?

This is the area where I want to add tracks and trails:

http://www.openstreetmap.org/?lat=50.4798&lon=-120.4541&zoom=14&layers=M 
<http://www.openstreetmap.org/?lat=50.4798&lon=-120.4541&zoom=14&layers=M>

This is a GPS trace I have uploaded:

www.openstreetmap.org/user/SRW/traces/1187039 
<http://www.openstreetmap.org/user/SRW/traces/1187039>

Thanks

Steve


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