Thread: does GIS DMS data type already exist?

does GIS DMS data type already exist?

From
vandewal@dhc.net
Date:
Hey,

I am builing a system that is going to be dealing with a large
amount of GIS (geographic) data from USGS.  Some of their data
provides lattitude and longitude in the DMS (degrees minnutes seconds)
format, other provides lat/lon in decimal format.  The decimal is
obviously not a problem for postgres, but the DMS is.  I am going to
need to be doing queries based on the DMS data, and will need it
treated as numeric instead of just a text string.

Soooo (to get to my question already!) what I want to know is
whether anyone else has already coded up a data type to do this
kind of thing or whether I just have to do it myself.

I search around but didn't find one.

Thanks for you time.

dv


// David E. Vandewalle          | The best diplomat I know is a fully
// vandewal@skyblue.com         | activated phaser bank.
// david.e.vandewalle@lmco.com  |     -- Scotty

Re: [GENERAL] does GIS DMS data type already exist?

From
Peter Eisentraut
Date:
Funny, just today I was thinking "Hmm, a DMS data type might be useful to
implement."

Right now there is no such thing (in the official sources anyway). Unless
you want to walk the long path of making up your own datatype (which we'd
appreciate, of course), you might be better off creating a conversion
function or two in the backend or letting the frontend handle the
conversion.

(Of course, if you do create conversion functions in the backend, you are
already half-way to having your own datatype.)

On second thought, perhaps you could abuse the time datatype. Of course
it's more like HMS, but perhaps you could make a spin off.

    -Peter


On Sat, 13 Nov 1999 vandewal@dhc.net wrote:

> Hey,
>
> I am builing a system that is going to be dealing with a large
> amount of GIS (geographic) data from USGS.  Some of their data
> provides lattitude and longitude in the DMS (degrees minnutes seconds)
> format, other provides lat/lon in decimal format.  The decimal is
> obviously not a problem for postgres, but the DMS is.  I am going to
> need to be doing queries based on the DMS data, and will need it
> treated as numeric instead of just a text string.
>
> Soooo (to get to my question already!) what I want to know is
> whether anyone else has already coded up a data type to do this
> kind of thing or whether I just have to do it myself.
>
> I search around but didn't find one.
>
> Thanks for you time.
>
> dv
>
>
> // David E. Vandewalle          | The best diplomat I know is a fully
> // vandewal@skyblue.com         | activated phaser bank.
> // david.e.vandewalle@lmco.com  |     -- Scotty
>
> ************
>
>

--
Peter Eisentraut                  Sernanders vaeg 10:115
peter_e@gmx.net                   75262 Uppsala
http://yi.org/peter-e/            Sweden


Re: [GENERAL] does GIS DMS data type already exist?

From
"Gene Selkov, Jr."
Date:
> On Sat, 13 Nov 1999 Peter Eisentraut wrote:
>
> Funny, just today I was thinking "Hmm, a DMS data type might be useful to
> implement."
>
> Right now there is no such thing (in the official sources anyway). Unless
> you want to walk the long path of making up your own datatype (which we'd
> appreciate, of course),

The path is not very long if you just want to solve the problem by
writing an extension in the form of a shared object. You'll have to
write a couple screenfuls of c code, a simple Makefile and a sql
script to craft your data type into the postgres schema. An
entry-level c student with two days of experience can easily do
this. I agree the documentation on extensions is somewhat lean, but I
can guide everyone wishing to write their own types through the entire
process. Contact me directly, we'll do a few iterations, then report
to the list.

However, if you plan on making your type a backend built-in or if you
want to make a configurable and portable extension, you and I could
use some help. I only know how to build shared objects for linux,
freebsd and sun/solaris. Someone's got to know how to add a built-in
type: there were much fewer types at the time when postgres left
Berkeley.

> you might be better off creating a conversion
> function or two in the backend or letting the frontend handle the
> conversion.

doing the conversion in the front end seems like a plausible idea if
you pick an adequate base type to represent your data. I would
advocate using the box type *both* for locations and rectangular areas
in geography -- that will account for efficient indexing and uniform
usage. Same idea if you build your own type -- make it equivalent to
the box type. One can also try and derive the type from the built-in
by writing special i/o and interface functions.

> On second thought, perhaps you could abuse the time datatype. Of course
> it's more like HMS, but perhaps you could make a spin off.

the time datatype is ok as long as your degrees are between zero
and 24. also, you won't be able to do the geometrical indexing on
it. Like I said, do your own, it's going to be fun!

--Gene

> On Sat, 13 Nov 1999 vandewal@dhc.net wrote:
>
> > Hey,
> >
> > I am builing a system that is going to be dealing with a large
> > amount of GIS (geographic) data from USGS.  Some of their data
> > provides lattitude and longitude in the DMS (degrees minnutes seconds)
> > format, other provides lat/lon in decimal format.  The decimal is
> > obviously not a problem for postgres, but the DMS is.  I am going to
> > need to be doing queries based on the DMS data, and will need it
> > treated as numeric instead of just a text string.
> >
> > Soooo (to get to my question already!) what I want to know is
> > whether anyone else has already coded up a data type to do this
> > kind of thing or whether I just have to do it myself.
> >
> > I search around but didn't find one.
> >
> > Thanks for you time.
> >
> > dv
> >
> >
> > // David E. Vandewalle          | The best diplomat I know is a fully
> > // vandewal@skyblue.com         | activated phaser bank.
> > // david.e.vandewalle@lmco.com  |     -- Scotty
> >
> > ************
> >
> >
>
> --
> Peter Eisentraut                  Sernanders vaeg 10:115
> peter_e@gmx.net                   75262 Uppsala
> http://yi.org/peter-e/            Sweden
>
>
> ************
>
>