[mapguide-users] RE: RE: Wish List

[Jim O'Leary]

Here's another PHP solution. Make a  MgCoordinateSystemTransform object and
use it with the
Transform() method of the geometry object that you get from
$featureReader->ReadNext().
In this case I'm transforming whatever the map's SRS is into BC Albers,
which is metric.

$BCALBERS =
'PROJCS["BC_Albers",GEOGCS["LL83",DATUM["NAD83",SPHEROID["GRS1980",6378137.000,298.25722210]],PRIMEM["Greenwich",0],UNIT["Degree",0.017453292519943295]],PROJECTION["Albers_Conic_Equal_Area"],PARAMETER["false_easting",1000000.000],PARAMETER["false_northing",0.000],PARAMETER["standard_parallel_1",58.50000000000000],PARAMETER["standard_parallel_2",50.00000000000000],PARAMETER["latitude_of_origin",45.00000000000000],PARAMETER["central_meridian",-126.00000000000000],UNIT["Meter",1.00000000000000]]';
$coordSysFactory = new MgCoordinateSystemFactory();
// Assuming you have opened the map...
$source = $coordSysFactory->Create($map->GetMapSRS());
$target = $coordSysFactory->Create($BCALBERS);
$transform = new MgCoordinateSystemTransform($source, $target);
// make the feature reader, and then...
while ($featureReader->ReadNext())
{
    $byteReader = $featureReader->GetGeometry('GEOMETRY');
    $geometryReaderWriter = new MgAgfReaderWriter();
    $geometry = $geometryReaderWriter->Read($byteReader);
    // Transform to BC Albers
    $geometry = $geometry->Transform($transform);
    $area = $geometry->GetArea();
}// end while
With further tests, you could determine if your geometry is a line or
linestring, and extract the length
instead of the area with $geometry->GetLength()



Kori Maleski-3 wrote:
> 
> Here is how to get area with a coordinate transform:   
> 
>  
> 
> Say - if my map is projected, but my data is in Latlong.
> 
>  
> 
>  
> 
>  
> 
>             If l_ofeatures.ReadNext() Then
> 
>  
> 
>                 Do
> 
>  
> 
>                     Dim l_oMgByteReader As MgByteReader =
> l_ofeatures.GetGeometry("Geometry")
> 
>                     Dim l_oGeometryReaderWriter As New MgAgfReaderWriter
> 
>                     Dim l_oMgGeometry As MgGeometry =
> l_oGeometryReaderWriter.Read(l_oMgByteReader)
> 
>                     Dim l_oMgPolygon As MgPolygon = l_oMgGeometry
> 
>  
> 
>  
> 
>                     'Get Current map projection
> 
>                     Dim l_sWKTproj As String = p_oMap.GetMapSRS()
> 
>                     'Create Coordinate System object to Reproject 
> 
>                     Dim l_oMGCoordinateSystemDestination As
> MgCoordinateSystem = l_oMGCoordinateSystemFactory.Create(l_sWKTproj)
> 
>  
> 
>   Dim l_sWKTproj As String =
> "GEOGCS[LL84,DATUM[WGS84,SPHEROID[WGS84,6378137.000,298.25722293]],PRIMEM[Gr
> eenwich,0],UNIT[Degree,0.01745329251994]]"
> 
>                     Dim l_oMGCoordinateSystemSource As MgCoordinateSystem
> =
> l_oMGCoordinateSystemFactory.Create(l_sWKTproj)
> 
>  
> 
>                     Dim l_oMGTransform As MgTransform
> 
>                     l_oMGTransform = New
> MgCoordinateSystemTransform(l_oMGCoordinateSystemSource,
> l_oMGCoordinateSystemDestination)
> 
>                     l_oMgPolygon.Transform(l_oMGTransform)
> 
>                     Dim l_dArea As Double = l_oMgPolygon.Area
> 
>  
> 
>                 Loop While l_ofeatures.ReadNext()
> 
>  
> 
>             End If
> 
>  
> 
>             l_ofeatures.Close()
> 
>  
> 
>  
> 
>  
> 
> a'la PHP flavour:
> 
>  
> 
>  
> 
> function GetTransform()
> 
>       {
> 
>             $coordSysFactory = new MgCoordinateSystemFactory();
> 
>             $resourceService =
> $this->site->CreateService(MgServiceType::ResourceService);
> 
>             
> 
>             $map = new MgMap();
> 
>             $map->Open($resourceService, $this->args['MAPNAME']);
> 
>             
> 
> $source =
> $coordSysFactory->Create("GEOGCS[LL84,DATUM[WGS84,SPHEROID[WGS84,6378137.000
> ,298.25722293]],PRIMEM[Greenwich,0],UNIT[Degree,0.01745329251994]]");
> 
>             $target = $coordSysFactory->Create($map->GetMapSRS());      
> 
>             
> 
>       
> 
>             return new MgCoordinateSystemTransform($source, $target);
> 
>       }
> 
>  
> 
>  
> 
>  
> 
>  
> 
> ________________________________
> 
>  
> 
>  
> 
>  
> 
>  
> 
> Kori Maleski
> 
> Senior Application Developer
> 
> WEBSOFT DEVELOPERS, INC.
> 
> P: (530) 759-8754 ext 114
> 
> F: (530) 759-0923
> 
> kori.maleski at websoftdev.com
> 
> ________________________________
> 
>  
> 
>  
> 
> -----Original Message-----
> From: mapguide-users-bounces at lists.osgeo.org
> [mailto:mapguide-users-bounces at lists.osgeo.org] On Behalf Of Jason Birch
> Sent: Tuesday, April 10, 2007 2:24 PM
> To: MapGuide Users Mail List
> Subject: RE: [mapguide-users] RE: Wish List
> 
>  
> 
> Hi Jim,
> 
>  
> 
> That's giving you the area in degrees, which is a nonsense number.  
> 
>  
> 
> You need to transform your LL geometry into a projected system like UTM
> 
> (or maybe BC Albers for your application?).
> 
>  
> 
> Jason
> 
>  
> 
> -----Original Message-----
> 
> From: Jim O'Leary
> 
> Subject: [mapguide-users] RE: Wish List
> 
>  
> 
> However, the number that I get is:
> 
>  
> 
> 0.00022107919307102
> 
>  
> 
> which does not seem meaningful.
> 
> _______________________________________________
> 
> mapguide-users mailing list
> 
> mapguide-users at lists.osgeo.org
> 
> http://lists.osgeo.org/mailman/listinfo/mapguide-users
> 
> 
> _______________________________________________
> mapguide-users mailing list
> mapguide-users at lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/mapguide-users
> 
> 

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