[Talk-ca] GeoBase import woes...

James Ewen jewen at shaw.ca
Thu Jan 22 05:46:25 GMT 2009


On Wed, Jan 21, 2009 at 8:58 PM, Dan Putler <dan.putler at sauder.ubc.ca> wrote:

> You shouldn't be ashamed. The guys who do this for a living do know
> something (and have really nice Trimble differential gps units).
> Besides, you are in Alberta, and the Alberta government (and the
> municipal governments in Alberta) has/have been one of the most
> cooperative with the Geobase effort up to this point.

Well, if you actually look at the quality of the data, you wouldn't be
that impressed. The quantity of data is impressive though.

I know one thing for sure... I'm going to beat the data around Fort
McMurray to death before I'm finished with it.

So, I tried another tack... I blew away some of my data that I had
traced out with my GPS, and inserted the GeoBase data. That works good
for getting the attributes in there, and stiches things together.
However, the quality leaves something to be desired.

Manually rearranging nodes, adding new ones to make the way more
accurately represent the real location of the roadway.

I'm thinking that perhaps a little from column A, and a little from
column B might be the best bet.

Playing with the data now has enlightened me a little bit. I'm
understanding a little more about how the GeoBase data is represented.
Ways represent a roadway between intersections, and can include any
number of nodes required to describe that way. At minimum, two nodes
are required, to define the ends of the way. GeoBase NIDs only are
associated with ways.

So, I'm thinking it should be possible to take a poorly defined
GeoBase way, and add more resolution to the description by adding more
nodes to the way. Anyone that has done some OSM editing will know that
it is probably easier to rip up a poor way, and start from new. So,
that leaves me wondering... do I add all the attributes to existing
GPS traced ways, or try and fix poor GeoBase ways.

I'm wondering if I should upload GeoBase ways on top of the GPS traced
ways, copy the attributes over, and align/stitch, then remove the
GeoBase way. I would also need to cut the GS traced ways into sections
that mimic the GeoBase ways. This is based on using Potlatch as my
editor. I'm not sure if there's a way to do the same thing in JOSM.

While the GeoBase data may have been collected by what is supposed to
be a higher accuracy data acquisition technique, I can sure find
places that do not support that observation. I also do not like the
fact that GeoBase depicts dual carriageways as parallel ways, but when
it gets to an intersection, it connects both ways to a single node.

James
VE6SRV




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