[Talk-ca] Users in Ottawa and Geobase

[Richard Degelder]

Ladies and Gentlemen,

James Treacy mentioned

On the other hand, there are many areas that have had the occasional,
inexperienced mapper enter a few roads. These are generally of low
quality and make a mess of the geobase import. These people are not
on talk-ca so never had a chance to say, 'replace my work as it is
of dubious quality.' Fixing the roads can be a lot of work in this
case. Much more than simply replacing the work and then fixing a few
modified intersections and moving some roads using data from gps
traces.

In spite of the second case, anyone asking about poor quality roads is
given the party line that the existing work should stay.

The data contributed by all contributors should stay regardless of the
apparent quality.

The OpenStreetMap wiki about imports (
http://wiki.openstreetmap.org/wiki/Bulk_Importing ) clearly states:

  "Bulk imports are undertaken as a supplement to data collected by
individual volunteers, and their data and ability to work in an area *always
* has priority."

which should be well regarded as a guideline for all of the imports in
Canada and abroad.  They do not differentiate between good quality and poor
quality work nor about the apparent quality of the imported data.  And the
imported data varies in quality as well.  Some of it is very high quality
Differential GPS but other areas are of a lower quality.  James Ewen has
stated, recently (Oct 25, 2009),

  "...  I tracked thousands of kilometres of
highway in the year before GeoBase became available, adding it to the
database, or replacing low resolution imagery tracings. Those highways
still exist in the OSM database, describing the route of the highways
in higher resolution than the GeoBase data does."

and, again from James Ewen (Oct 25, 2009),

"...One can not automatically
assume that the GeoBase data is of higher quality than the OSM data
simply because there are more tags associated. In some cases, the
positional accuracy of the GeoBase data is better than OSM data, but
in other instances, the OSM data positional accuracy is better than
GeoBase. It all depends upon the amount of effort expended during the
input process."

Among the tags for the GeoBase import there is usually a tag describing the
source of the original data from the municipality and it varies with age and
location.  Now do you want to replace higher quality data submitted by a
user, even if that user has contributed little and nothing for a while, with
something from GeoBase that is not really accurate?  I have updated data
that was imported as part of the GeoBase import that was certainly not as
accurate as it should, and could, have been so I personally know that the
GeoBase import is not always the best source of data.  On the other hand I
am grateful for the data being available sine it is sometimes the only way
we are going to get data for some areas within a reasonable time frame, or
even our lifetimes.

If you are in the area that you are looking at the best, and really only,
option is to check out the area yourself with a GPS and to correct any
discrepancies regardless of if they were made by a individual mapper or as
part of the GeoBase import.  It is possible to modify the data regardless of
the source and doing so improves the map.  Replacing all of the user
contributed data automatically with GeoBase data is not the answer and can
even cause errors because the GeoBase data is not always the most current
either.  So update, and correct, the data regardless of the source by
physically checking it, preferably with a GPS.
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