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

Sat Feb 6 01:06:15 GMT 2010

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

jsmart09's diary
*2010-02-04<http://www.openstreetmap.org/user/jsmart09/diary/9477>
*

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parts are just as out of date in the newest edition (well actually they're
more out of date!).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<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%5Btextzoom03%5D%3DFEATURE+POINTS+2169671.31541+142309.976588+END+TEXT+%22Oromocto%2BRiver%22+END%26map.layer%5Btextzoom46%5D%3DFEATURE+POINTS+2169671.31541+142309.976588+END+TEXT+%22Oromocto%2BRiver%22+END%26map.layer%5Blineresultzoom0%5D%3DDATA+fap_rivers%26map.layer%5Blineresultzoom1%5D%3DDATA+fap_rivers%26map.layer%5Blineresultzoom2%5D%3DDATA+fap_rivers%26map.layer%5Barrowzoom03%5D%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 <http://www.openstreetmap.org/user/jsmart09> at Fri, 05
Feb 2010 02:51:03 +0000 in English
(English)<http://www.openstreetmap.org/diary/en>
------------------------------
Comment from acrosscanadatrails<http://www.openstreetmap.org/user/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
OpenStreetMap IRC: http://irc.openstreetmap.org
@Acrosscanadatrails
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