[Imports] Fw: Re: tiff, dwg and nad83

[Frank Cox]

On Sat, 14 Apr 2012 13:44:15 -0700
Paul Norman wrote:

> I'll link to http://wiki.openstreetmap.org/wiki/Import/Guidelines at the
> start since it contains the guidelines.

Thanks.  There are six million pages of stuff on the wiki and finding what I
need to know on my own appears to be next to impossible.  Of course, I don't
yet know enough about this to form intelligent questions so that's a big chunk
of the problem right there.

> It's generally best if a local user converts and uploads the data. 

I guess that would be me.  If I can find out how to do that conversion and
upload.

> If they have tiffs and DWG files they likely have aerial photos (GeoTIFFs)
> and geodata. The standard format for geodata from GIS departments is in a
> shapefile (.shp) but it should be easy to convert between .dwg and .shp.

He did mention aerial photos of some kind but again, I didn't know enough about
it to follow that aspect up at the time.

If that's what we actually want, then I can certainly ask him about it this
week.

> Both can be useful. City aerial photos tend to be more accurate than Bing
> and frequently higher resolution. Geodata can sometimes be useful for
> importing, but it takes some work to get it converted to .osm.
> 
> There are essentially two parts to the conversion, there's the conversion of
> the geometry and the conversion to OSM tags. The first is easy, there's
> several programs that will do it.

Dandy.  I was thinking that at least some of this should be as simple as running
a conversion program.  And if it takes a while to run, meh.  I've got lots of
computers; they might as well be earning their keep.

> The second requires looking at the
> shapefile tags and converting them to OSM tags. Local knowledge helps here.
...
> You have to write a translation file for it. This requires knowing, for
> example, that what the city calls a "Collector" road is what OSM calls
> highway=tertiary. 

Is there some kind of a glossary or reference to what these things are or are
expected to be?  I'm not an engineer, surveyor or even a GPS hobbyist.  I run a
movie theatre and play with computers.

> Legally, the easiest would be if they provided the data on their website
> under a license like PDDL. This is what some cities locally have done with
> their open data initiatives.

I would really like to have some reasonable level of confidence that I can
actually do this before making an official approach to the City.  I don't want
to get an official go-ahead from the City Council, create a set of
expectations (that will probably end up getting reported in the local
newspaper), and then find out that it won't work for whatever reason. 

If I can get a set of directions that tell me to do x, then do y, my idea is to
get a small subset of test data from the engineering department and try this
thing out. If it works, dandy, lets roll the bandwagon.

> Running linux is an advantage. Most of the instructions are for Ubuntu, but
> you should be able to adapt them to Centos easily enough. The shapefile
> conversion tools are easy to install. If you want to serve the geotiffs to
> yourself there are a few options but it would be best to see how big they
> are first. Geotiffs can range from a few gigabytes for a city to a few
> hundred gigabytes. The techniques for hosting vary depending on the size.

Since I wouldn't know a geotiff (or a shapefile) if I met one on the street, I
can't provide any more information about that without asking more questions on
this end.

What questions I should be asking?

> Something else you might want to look at is
> http://wiki.openstreetmap.org/wiki/CanVec. CanVec is best when it's used by
> a local in combination with their area and it can save a lot of otherwise
> tedious work.

If I understand what I've just looked at, it appears that this data is probably
something similar to the engineering maps that I started this topic to discuss,
with (perhaps) less detailed data included.  Is that correct?


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-- 
MELVILLE THEATRE ~ Real D 3D Digital Cinema ~ www.melvilletheatre.com
www.creekfm.com - FIFTY THOUSAND WATTS of POW WOW POWER!