[Talk-ca] jsmart09's diary (canvec/ geobase discussion)

Sat Feb 6 02:04:30 GMT 2010

Hello Sam

Yes I took an initial look at this stuff back in
November or so but got stuck at a python problem. Taking another look at it
now. I decided to try to write a few notes in my diary to record my
learning experience, mostly for my own benefit at this time. I had not
realised at first that it is a public diary but I did see that later.

At this point I am learning, with a view to contributing some to the
map. Eventually I will probably put some Canvec data in and improve
some of the NB mapping (roads) that are there. If I have any questions
I'll be sure to ask. Probably if I do stick some data in I will ask for
people to review it to be sure I am doing the "right" thing.

I have also browsed talk-ca a bit and there is much more I could learn in there I'm sure. I see your name in there a lot :)

John

________________________________
From: Sam Vekemans <acrosscanadatrails at gmail.com>
To: Talk-CA OpenStreetMap <talk-ca at openstreetmap.org>
Sent: Fri, February 5, 2010 9:06:15 PM
Subject: [Talk-ca] jsmart09's diary (canvec/ geobase discussion)

Hi, Just forwarding this message,
It looks like we have someone interested in helping solve the CanVec.Geobase Hydrography delema :-)

jsmart09's diary2010-02-04

Today I have looked through the Canvec documentation, which is here: http://geogratis.cgdi.gc.ca/geogratis/en/collection/28954.html
In particular, the Data Product Specifications http://ftp2.cits.rncan.gc.ca/pub/canvec/doc/CanVec_product_specifications_en.pdf
and the Feature Catalogue: http://ftp2.cits.rncan.gc.ca/pub/canvec/doc/CanVec_feature_catalogue_en.pdf
I want to understand these so that I can understand the rules files that Sam Vekemans has set up.
Incidentally Geobase or Canvec? From what I can see Geobase is an
initiative, to bring in data from multiple authorities. There is a
variety of types of geo data. Canvec is basically the NTS topo map data
but it has been reformatted / remodelled. New editions of Canvec are
brought out, apparently every 6 months. We are onto edition 4 for NB at
least for Fredericton area. The actual spatial data rarely seems to
change and some parts are just as out of date in the newest edition
(well actually they're more out of date!). 
NRN (National Road Network) has been incorporated into Canvec so
there seems to be no difference in the data whether you get roads from
Canvec or from NRN files.
How to figure out what SHP file some entities / objects are in? Two
letter code indicates general theme e.g. HD is hydrography, TR is
transportation, TO is toponymy. Within the theme, there is a 7-digit
code that indicates the entity type (what I'd think of as "object
class"). E.g. 1480009 is the generic code for a Waterbody. Geometry
(point, line, area) is split out into separate SHP files. So we have
e.g.
021g15_4_0_HD_1480009_2.shp for:
NTS tile 021G15 
Edition 4 
Version 0 
HD for hydrography 
1480009 for waterbody objects 
2 for area geometry
Inside this SHP file there are all the waterbody objects for the area of 021G15.
To encode the particular types of waterbody object there are further
7 digit codes, stored as the value of the CODE attribute. E.g. a CODE
1480272 is an "unknown / non-isolated" waterbody. A 1480092 is a
"liquid waste, isolated" waterbody (i.e. a sewage holding pond)
Hydrography: I thought it might be simple to get lakes and rivers
out of Canvec, but some of the data is a bit strange. In 021G15 I have
Mactaquac Lake and a big chunk of the St John River as the same area
object. In Edition 3 it all had the name "Mactaquac Lake". Edition 4
has removed the name. Likewise for the Oromocto River, a bunch of lakes
adjacent to the river are all bundled into the same area object as the
river. 
So how does Toporama -
 http://atlas.nrcan.gc.ca/site/english/maps/topo/map?mapsize=1150%201350&lat=45.85204497&long=-66.48944242&mapxy=2170329.14209+130644.561916&scale=5000000&feature_na=Oromocto+River&location1=13&unique_key=0c803390849c20c3b25c26ef7b645fbd&searchstring=oromocto%20river&entity=RIV&layers=fapfeature+nodata_ntdb_50k%20north_arrow%20other_features%20roads%20hydrography%20boundary%20builtup%20vegetation%20populated_places%20railway%20power_network%20manmade_features%20designated_areas%20water_features%20water_saturated_soils%20relief%20contours%20toponymy%20contour&urlappend=%26unique_key%3D0c803390849c20c3b25c26ef7b645fbd%26map.layer[textzoom03]%3DFEATURE+POINTS+2169671.31541+142309.976588+END+TEXT+%22Oromocto%2BRiver%22+END%26map.layer[textzoom46]%3DFEATURE+POINTS+2169671.31541+142309.976588+END+TEXT+%22Oromocto%2BRiver%22+END%26map.layer[lineresultzoom0]%3DDATA+fap_rivers%26map.layer[lineresultzoom1]%3DDATA+fap_rivers%26map.layer[lineresultzoom2]%3DDATA+fap
_rivers%26map.layer[arrowzoom03]%3DFEATURE+POINTS+2169671.31541+142309.976588+END+END
manage to get nice-ish looking lake and river names? Answer: there
are TO (toponymy) theme point objects which have been digitized
someplace inside the waterbody. As I mentioned above the waterbody
could encompass multiple lakes and rivers. There is no relationship at
all between the toponymy objects and the waterbodies.
TO objects seem to have a generic theme number 1580009. Each object
also has a CODE but its value always seems to be 1580010, for all the
names I've looked at. There is an additonal attribute, CONCISECODE, and
this is the one which differentiates e.g. French Lake (the lake,
CONCISECODE=150) from French Lake (the hamlet, CONCISECODE=80).
Actually if you look at the Feature Catalogue you can see that 80 is an
"unincorporated area).
How does OSM deal with area names? It seems it's all free and easy
and varies depending on your mood. I looked at a lake or two in Maine
and the area objects had no names but there were point names, like
Canvec has. I also looked at a couple of lakes in Switzerland and saw
that they had names as attributes of the lake edges. The Osmarenderer
seems to pick up those attributes for display as names (if you zoom in
far enough...) (Which raises another topic: where are the rules for the
renderer? If I knew that, I could figure out what attributes are useful
to include and what names to give them.. I think).
Back to the Canvec data. If I want to use the hydrography, I just
don't like the approach of the unrelated point objects. I'd prefer to
make the name an attribute of the area object. That would mean I had to
split up those humungous waterbodies into separate lakes and rivers.
More work. Should I do it the simple way first then make another pass
later to improve? Seems like the better approach.
Maybe tomorrow I shall take another look at Sam Vekeman's rules
files with a view to running the shp-to-osm.jar app to generate some
.osm from one or two .shp files. Then I'll look at those in e.g. GM.
I'll get a feel for what attribution the .osm is going to have. I
should try to find whether there is any accepted standard for
attribution for Canada at least. 
Question (to myself, rhetorical!): do we want to 
Posted by jsmart09 at Fri, 05 Feb 2010 02:51:03 +0000 in English (English) 
________________________________

Comment from acrosscanadatrails at Sat, 06 Feb 2010 01:04:33 +0000
Hi, I've emailed the talk-ca at openstreetmap.org list, and copied your
message, please join the list, as im sure others would be interested to
hear from you.
Cheers, 
Sam Vekemans 
acrosscanadatrails at gmail.com

Twitter: @Acrosscanada
Blog:  http://Acrosscanadatrails.blogspot.com
Facebook: http://www.facebook.com/sam.vekemans
Skype: samvekemans
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@Acrosscanadatrails
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