[Talk-ca] Modifying GeoBase Ways.

[Bégin, Daniel]

Hi James,

I have two comments ...

1- replacing ways
I don't know the accuracy of a Blackberry but using a garmin gpsmap 60csx (waas on), I sometime get a 10 meters offset between tracks for the same way!  

So, be cautious before deleting a way that doesn't match your gps track, unless you have multiple tracks that confirm the way is wrong.  For your information, accuracy of geobase/canvec road segments over Alberta is usually within 2-6 meters.


2- using geobase/canvec attributes
If you consider that the way should still be replaced with your gps track, then it is yours! I dont see why geobase/canvec stuff would be kept.  

If you keep the original way but change lanes=2 for lanes=1.5 (let say lanes=1!), I would then keep geobase/canvec stuff.  I thing that the osm database will keep a record that you had changed the value of the "lanes" tag. 

By the way, lanes=2 seems to be a kind of default value when data source is Orthoimage.

Daniel





-----Original Message-----
From: talk-ca-bounces at openstreetmap.org [mailto:talk-ca-bounces at openstreetmap.org] On Behalf Of James Ewen
Sent: 15 novembre 2009 18:52
To: talk-ca
Subject: [Talk-ca] Modifying GeoBase Ways.

Okay, I need some advise...

I drove a nice little twisty back road today, and captured it with my Blackberry. I have the trace uploaded to OSM, and have looked at it in relation to the GeoBase way.

GeoBase Way
http://www.openstreetmap.org/browse/way/31847379

GPS Track
http://www.openstreetmap.org/user/VE6SRV/traces/566355

The GeoBase way has an acquisition source of Orthoimage, and it is a little less than a perfect representation of the real way. My GPS track would appear to do a better job of representing the actual way.
If I were to replace the existing way with a copy of my GPS track, what should I do with the tags? Do I copy all the tags over?

I would plan on replacing the existing way with a track made from my GPS trace.

highway:tertiary, is_in: Camrose County, name:Range Road 204a, surface:unpaved will all stay, as they are all still valid descriptors.

Should attribution stay? The way is no longer from GeoBase, but the tag information would be.
Same for the source tag... some information is from the Geobase_Import_2009, while some is not.
geoBase:acquisitionTechnique is no longer Orthoimage, but should this be replaced by a tag stating that it is now GPS tracked?
Do I leave the geobase:datasetName:NRN:Alberta, or should that go?
I think the geobase:uuid tag should stay to allow future identification against the GeoBase database.
lanes:2 probably needs a tweak. The twisty part of this road is not what I would consider 2 lanes. Meeting a regular sized vehicle would require both vehicles to nearly stop, and pass each other with two wheels in the ditch each. I would call this at best 1.5 lanes wide.

So, what to do, what to do???

James
VE6SRV

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