[fdo-users] Spatial conversion

Tue Feb 13 13:57:39 EST 2007

In order to have some Coord. System information, one must use a .PRJ file.
For the Hawaii dataset there is one in the SHP provider /TestData/Hawaii/ folder. For convenience, it is attached.

Dan.

-----Original Message-----
From: Ytse [mailto:bill_gfr at yahoo.fr] 
Sent: Tuesday, February 13, 2007 6:05 AM
To: Dan Stoica; Gavin Cramer; fdo-users at lists.osgeo.org
Subject: Re : [fdo-users] Spatial conversion

Dan> 
Hum first of all I forgot to mention I'm working on SHP files (guess that can change things, as spatial context is only listed as "get spatial context = Y" in provider capabilities)

everything is empty ("") except for name which is "Default"
Here's the code I use
            // spatial context
            IGetSpatialContexts get;
            ISpatialContextReader screader;
            get = (IGetSpatialContexts)connection.CreateCommand(OSGeo.FDO.Commands.CommandType.CommandType_GetSpatialContexts);
            screader = get.Execute();
            while (screader.ReadNext())
            {
                Console.WriteLine("Context Name : " + screader.GetName());
                Console.WriteLine("Context Description : " + screader.GetDescription());
                Console.WriteLine("Context Coordinate System WKT : " + screader.GetCoordinateSystemWkt());
                Console.WriteLine("Context Coordinate System : " + screader.GetCoordinateSystem());
            }
I have only one shp file in the directory, "hawaii.shp" from the internet (I've also tried with 

Gavin> thank you, I'll try to investigate this (would you recommend focusing on PROJ.4 or trying teh more recent LIBPROJ4 ?)

I'm using Mapguide Server 6.5 but never had to use its API before (exwcept fo SdfToolkit and MapGuide Viewer). I had found another conversion library (ConversApi.dll) but I can't use it as it requires to write into the registry during runtime.

----- Message d'origine ----
De : Dan Stoica <dan.stoica at autodesk.com>
À : Gavin Cramer <gavin.cramer at autodesk.com>; Ytse <bill_gfr at yahoo.fr>; fdo-users at lists.osgeo.org
Envoyé le : Lundi, 12 Février 2007, 17h42mn 44s
Objet : RE: [fdo-users] Spatial conversion

" ... but I haven't obtained anything else that "Default" in GetName() for my test files ?"

GetName() returns the name of the Spatial Context.
Look for GetCoordinateSystem() and GetCoordinateSystemWkt() for info pertaining the Coordinate System.

Dan.

-----Original Message-----
From: fdo-users-bounces at lists.osgeo.org [mailto:fdo-users-bounces at lists.osgeo.org] On Behalf Of Gavin Cramer
Sent: Monday, February 12, 2007 11:28 AM
To: Ytse; fdo-users at lists.osgeo.org
Subject: RE: [fdo-users] Spatial conversion

FDO does not itself support coordinate conversion.  What you will get from the Spatial Context is the name or definition of a coordinate system.  There are several ways to get do what you want...

1.  If you are using MapGuide, its API can do it.  The open-source version effectively results in the next approach...

2.  Use OGR directly.  Both this solution and #1 above will result in calls to PROJ.4 (http://www.remotesensing.org/proj/).

3. Spin your own solution, using whatever general solution (like PROJ.4) that you have available.  You can save time coding access to the FGF content by using a handy example class that sits in GeometryTest.cpp, in the FDO unit test.  Look for the GeometryConverter class.  You just have to fill in or override the ConvertPosition() methods to call whatever conversion package you choose.

I haven't worked much directly with the components for #1 or #2 above, so hopefully someone else will give more details if one of those fits your case.

Gavin

-----Original Message-----
From: fdo-users-bounces at lists.osgeo.org [mailto:fdo-users-bounces at lists.osgeo.org] On Behalf Of Ytse
Sent: Monday, February 12, 2007 9:38 AM
To: fdo-users at lists.osgeo.org
Subject: [fdo-users] Spatial conversion

Hi everyone, 

are there any ways to convert coordinates from one system to another using FDO ? 
(In my case that would be from LAMBERT IIe to WGS84)

By the way I know my files are in this system, but is it possible to detect it using FDO ? 
I thought I'd be able to do this by using using OSGeo.FDO.Commands.SpatialContext but I haven't obtained anything else that "Default" in GetName() for my test files ?

thank you

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