[mapserver-users] projections [shpmidx] [shpmidy]

[Armin Burger]

Another possibility for re-projecting shapefiles are the shapelib tools
(http://gdal.velocet.ca/projects/shapelib/) the 'shpproj' executable can
project shapefiles quite fast. There is also a compiled version for
Windows.

Armin

> Another little issue that has bothered me over time. Should shpmidx
and
> other similar parameters be returned in the map projection or their
> native projection. You've found out that the latter is the current
> behavior. I'd appreciate opinions one way or another. I've always
viewed
> query output as being pure, but if you look at the way WMS works you
> certainly have that control. I'd like to get this resolved for 3.7.

> Projection-wise, you'll definitely see better performance if you
> pre-project. On windows I don't know a tool, other than ArcView and
such
> that you can do this with. I submitted a perl script to the Wiki to do
> this with MapScript on the UNIX side of things. If you've got a linux
> box laying around you could make use of that.

> What I, or someone else should do is set up a projection service on a
> website. Upload a shapefile with a projection definition and return a
> new shapefile.
> Anyone? Anyone? (it would be easy with that perl script...)

> Steve

> Stephen Lime
> Data & Applications Manager

> Minnesota DNR
> 500 Lafayette Road
> St. Paul, MN 55155
> 651-297-2937

>>>> "Marco" <marco at mediaeval.nl> 09/11/02 02:14AM >>>
> Hi list,

> If the next question is a stupid one, excuse me. I am newbe.

> context:

> I use mapserv CGI (no mapscript) and a Apache webserver with PHP (on a
> windows machine for testing). I am building a web-application with
> dynamic maps.

> problem:

> I use a template file to get information about the map-features on the
> current map. The tags [shpmidx] and [shpmidy] provides information on
> the exact position of a feature (see
> http://mapserver.gis.umn.edu/doc36/template-reference.html ).

> With simple lineair algebra it is possible to calculate the
xy-position
> of this feature on the actual generated image. (a lineair
transformation
> from "real world" lat-lon coordinates to "image" x-y
pixelcoordinates).
> I use these information to create some kind of javascript rollover
> interface; if the mouse hovers a feature, the webapplication respons
> immediately, without the need of connecting to the server.

> So far so good. Everything works fine. So now for the problem. If I
> deploy a projection ("proj=stere") Nothing works anymore. That is
> because [shpmidx] and [shpmidy] gives the lon-lat stuff, but i need
the
> xy coordanates on the generated image of the map. Sure it should be
> possible to write transformations for projected maps (a lot of sinus
and
> cosinus, arctangens etcetera i suppose) but i believe that's a ticket
to
> the nearest snake pit.

> Is there a solution for this (withhout the need of writing my own
> transformation formulas)

> Or, if I have to write transformation, does anybody now the formulas
> for this projection:

> PROJECTION

> "proj=stere"

> "lat_0=52.156160556"

> "lon_0=5.387638889"

> "k=0.0000999908"

> "x_0=0.000"

> "y_0=0.000"

> "ellps=bessel"

> END




> Cheers,

> Marco




> Marco Pieck, marco at mediaeval.nl
> Mediaeval Vorm & Visie
> http://www.mediaeval.nl/
> postbus 1050, 6501 BB  Nijmegen,  the Netherlands
> tel: ++ 31 24-3818196, fax: ++ 31 24-3818183