A couple of points...
Brad Douglas wrote:
On Sun, 2007-10-07 at 23:08 +0100, Dave H wrote:
O.k thanks for that - I'm no geo-whatever expert - in fact most of the
acronyms
floated in here mean very little - i suspect to many this side of the
Ocean.
I am a geo-whatever expert. ;-) Most of acronyms used here are used in
the Geographic Information Systems (GIS) and geo-informatics industries.
It's a small, large industry in the sense that it is everywhere, yet few
have heard of it.
Glad to have you. I do a little in the industry, too, with the
technical committee of the Open Geospatial Consortium. I'm currently
active on the Defense-Intelligence working group and Sensor Web
Enablement. I'm also working with the somewhat fractious Coordinate
Transformations ad hoc group, which I think will achieve a working group
status in December.
It seems to me your so lucky in the US that your public-tax-$
investments in
geo-data collection - the data seems to be handed back freely back to
you..
Certainly in the UK either we have no of our own or its damn-secret or
we
have to pay a second time.
This is true that the US has been inherently blessed in the past with
good quality data. This is changing at a fast (and IMO, alarming) rate.
There really hasn't been truly freely available orbital data since
LANDSAT-7 and the SRTM shuttle mission.
Depends on your sources. Data here in Texas are good, free, and readily
available.
Street and feature data extracted from Census data is really a byproduct
of the Census, complete with varying amounts of error. This error can
be easily demonstrated on this page a friend did on the subject:
http://casoilresource.lawr.ucdavis.edu/drupal/node/433
Nice site. Had not seen that before, but it's interesting.
Unfortunately, Census, who uses the old DRG/STDS mapping info from USGS,
also munges the data for their purposes. I really wish they'd not made
their data widely available and so discoverable since they don't
maintain good (or adequate or even minimal real) metadata.
Unfortunately, a simple affine isn't always satisfactory, nor is the
affine transform matrix consistent for more than a small area (with
"small" being somewhat relative). Wish it was true but to correct all
of Tiger, you'd not only have to do all the county offerings, but
actually would end up subsetting some and doing unique transformations
to get them all right.
I've suggested that at a minimum, OSM should include metadata specifying
projection parameters, but it falls on deaf ears. It would be much
better if users either uploaded data consistently (and rejected
outliers) or the system reprojected upon upload.
I'd be able to come up with a minimum metadata list, but I fear I'd hit
the same response as you already have. At a minimum I'd love to know
what datum is being used and then transform to a common datum, ITRF2000
or WGS84 (2005).
OSM may be a useful last resort for Xastir in areas where better data
does not exist.
Unless you're thinking you'd get better data in Europe with OSM than you
can find now, OSM looks too sparse to be of a lot of use, anyway.
Xastir in the UK is often poor looking simply due to lack of decent
map sources
and probably zero overlays. Either we don't have them or some buggers
got
copyright over things we paid for once already. We get desperate or
use outlines
for lack of much else.
Aside from Census data, that is largely the case here in the States,
too.
Ordinance Survey tell me (and I asked specifically about this at the
summer OGC meeting) they are working on a policy statement and fee
structure to provide data of this sort to certain users at solely cost
recovery. Should happen this calendar year. And radio amateurs are now
added to the list. I confirmed this 2 weeks ago at the Fall OGC meeting.
I don't know how things of this nature function in the UK, but here we
are able to request data from local municipalities. I've had no trouble
getting needed data for projects that local governments have collected.
Have you tried asking various levels of government for a Shapefile of
roads? Try asking for street center-lines, first. They are generally
high accuracy. Be specific of what you want so that you aren't creating
work that they don't need to do...and they might respond to you
favorably in the future.
Lots of municipalities here and over on the other side of the pond have
a fee-recovery system. Sometimes I can get their data by asking,
sometimes by paying, and sometimes I have to use other means, like going
to their state or the Feds. I expect you'd see the same thing in UK.
gerry
--
Gerry Creager -- [EMAIL PROTECTED]
Texas Mesonet -- AATLT, Texas A&M University
Cell: 979.229.5301 Office: 979.458.4020 FAX: 979.862.3983
Office: 1700 Research Parkway Ste 160, TAMU, College Station, TX 77843
_______________________________________________
Xastir mailing list
Xastir@xastir.org
http://lists.xastir.org/cgi-bin/mailman/listinfo/xastir
