[OSM-talk] A plea for meaning ful changeset comments

[John F. Eldredge]

Well, in my area at least (Nashville, TN, USA), the aerial images seem pretty well aligned with the actual street locations.  The corrections I am speaking of tend to be needed only here and there, not overall.  Much of the street location info on the OSM map in my area originated in the TIGER import (data collected, over decades, by census-takers), and some of the original mappers were pretty sloppy.  You will have a neighborhood where all of the streets align with the aerial view, for example, except for one street that will be mapped 15 meters or so to the side of its actual location.

-------Original Email-------
Subject :Re: [OSM-talk] A plea for meaning ful changeset comments
From  :mailto:a.errington at lancaster.ac.uk
Date  :Sat Jul 31 01:29:02 America/Chicago 2010


On Fri, 30 Jul 2010 21:27:43 John F. Eldredge wrote:
> I have to admit that I am bad about not bothering to enter a comment,
> particularly if all I have been doing is fixing the alignment of streets to
> better conform to the Yahoo aerial view.

<snip>

Don't forget, the Yahoo! aerials might not be exactly aligned in all areas.  I
have found here in Korea the aerials are a little off in some places, but
correct in others.  I generally move the aerial layer until some obvious
feature lines up with a GPS trace (either my own, or downloaded), then I
start tracing other features from the aerials.  For example, in my town the
aerials are off by about 10m south and 8m east.  I have to slide the layer up
and left to align to the GPS.

Of course, it's true the GPS traces are also off by 5, 10, or more metres, but
you can overcome this by taking the average of many traces along the same
road.  In my case, the obvious aerial feature I use is an oval running track.
I have collected several GPS traces of this track, and they all agree with
each other.

I apologise if you silently inferred that "of course I align the aerials first
before I start fixing streets", but maybe this is new information for some
people.

Best wishes,

Andrew

PS I always try and put some changeset comment in, but I had/have no idea if
anyone reads them.  I also make mistakes such as not changing the comment if
I do two changesets in a row, or sometimes leaving the comment blank.  Oh
well.

_______________________________________________
talk mailing list
talk at openstreetmap.org
http://lists.openstreetmap.org/listinfo/talk

-- 
John F. Eldredge -- john at jfeldredge.com
"Reserve your right to think, for even to think wrongly is better than not to think at all." -- Hypatia of Alexandria