I think I see where you're coming from Chris, and I'm for standards
and existing toolsets. I think what we're talking about here is much
more simple.
Eventually we'll (hopefully!) get to the point where we want to define
polygon boundaries for Geo records and that sort of thing, and doing
so with Well Known Text (or even GML) might be a great way to go and
would simplify the data model a lot.
For now all we're looking for is a point location for an address, and
possibly other things too. Actually, I kind of like the idea of having
another ContactMechType for a terrestrial position, and maybe add some
sort of positionContactMechId to the PostalAddress entity to point to
it for an address.
In any case, we want to keep this simple because chances are we will
not use it with a GIS package, unless perhaps to pass the coordinates
to something to determine if it is within a boundary or something.
More likely we'll use really simple square or circle boundaries and
such which are a lot easier to search within using any database using
numerical coordinates, and those are easy since we're just talking
about point coordinates.
Of course, if someone wants to get into real GIS stuff and enhance the
Geo and other entities in OFBiz for that... by all means please go for
it!
-David
On Jul 2, 2008, at 4:42 PM, Chris Howe wrote:
David,
I stand corrected on the significant digits used in TIGER. It seems
there is a slight difference in unit specificity in the projection
that I assumed versus what TIGER provides
4269 degree Unit = 0.01745329251994328
Tiger degree Unit = 0.017453292519943295
This threw off the retrieval calculation of the coordinates and
didn't result in round numbers at the 6th decimal place and thus was
calculated to the maximum significant digits of the library (15
digits).
In regards to what I'm suggesting: I am simply suggesting that we
use the standards that have existed for over a decade for the
storage of geometrical data, namely Well-Known-Text or Well-Known-
Binary. The reason I am suggesting this is because you've already
submitted a desire to perform calculations that have been optimized
under libraries that use WTK/WTB. The other reason that I am
suggesting this is that latitude and longitude is not the only
coordinate system that would benefit from using the standard. For
instance, if someone has an RFID grid in their warehouse, they could
benefit from the same conventions being used.
In regards to "What about the other databases?": I can't imagine
the other databases with spatial extensions would require approaches
that were much different to benefit from GIS. PostGIS happens to be
an implementation of the OGC standards, so databases that have an
implementation of that standard would benefit from code written to
that standard.
The GeoTools Module Matrix plugins should give you an idea if you're
concerned about connecting to other databases.
http://geotools.codehaus.org/Module+Matrix
David E Jones <[EMAIL PROTECTED]> wrote:
Here is what I found in a quick search:
"Coordinates in the TIGER/Line® files are in decimal degrees and have
six
implied decimal places. The positional accuracy of these coordinates
is not
as great as the six decimal places suggest."
That is from near the bottom of page 6 of this document:
http://www.census.gov/geo/www/tiger/tigerua/ua2ktgr.pdf
Or are you referring to a different TIGER?
BTW Chris, I'm having a lot of trouble understanding your posts. I
don't know if others are running into the same thing, but much of the
time I'm not sure quite what you're getting at or what you propose as
many of these seem to be little snippets of thought instead of entire
thoughts... could explain a little more of what you have in mind?
Also: I looked at the postgis stuff you added, and... what's the
point? If it only works with postgres how is that useful for OFBiz?
-David
On Jul 2, 2008, at 4:31 AM, Chris Howe wrote:
In addition, TIGER road data is to 15 significant digits as is US
data for county political boundaries.
Chris Howe wrote: Roland wrote: Hi David,
as I wasn't really sure about what to answer to your question, i
looked a bit
around:
http://geocoder.us/blog/2006/03/23/how-many-digits-are-enough/
if their data is correct: 0.000001 degrees are 4.37184 inch or
11.1044736
centimeters
that ought to be enough for everyone ;-)
seriously: I think for applications like mapping out addresses that
should be enough for years, but there may be other use cases i can't
imagine right now.
--Roland
640K ought to be enough for anybody. This reminds me of another
benefit to WTK/WTB. WTK and WTB are not dependent on the coordinate
system you are using. Whether your coordinate system is the
latitudinal and longitudinal circles of the earth or whether they
are the coordinate system of your RFID enabled warehosue, WTK and
WTB handles them the same. Same data format, same use of
projections, same reliability in application you build. Why record
the same type of information in 15 different formats based on their
use?
