MapGuide OS with Google Earth

Mon Apr 10 12:36:36 EDT 2006

Hi,

Something that I've recently figured out is that it's a lot easier to
debug Mg errors if you wrap your code in Try/Catch.  Have a look at some
of the code in the mapadmin area, or in the package command line
utilities I posted about yesterday.

I wonder if the geometry column for your data source is the same as the
sample data (SHPGEOM).

You can see what this is supposed to be by looking at a layer based on
that feature source in Studio, under "Feature Data Setup".  You can also
get this information by going into the mapagent/index.html file,
clicking on Feature Service API in the upper left, then clicking on
Describe Feature item, and finally fill in the FeatureSource ID 

Library://Bolsward/Data/Data/totaal_tvg32010101_v.FeatureSource

The sample data definition looks like this:

  <xs:complexType name="HydrographicPolygonsType" abstract="false"
fdo:geometryName="SHPGEOM">

The fdo:geometryName attribute is what you want here.  

A better solution would be to let the code extract the geometry
column... hmm... bit of research later:

You could replace this line:

  $byteReader = $featureReader->GetGeometry('SHPGEOM');

With this:

  $byteReader =
$featureReader->GetGeometry($featureReader->GetClassDefinition()->GetDef
aultGeometryPropertyName());

Note that this isn't very efficient; it checks the default geometry
property on each feature object.  It would be better to do this outside
of the loop, or at the top of the loop in a section that's only executed
once.

Jason

________________________________

From: Willem Schwarte [mailto:willem at giskit.nl] 
Sent: Monday, April 10, 2006 07:38
To: Jason Birch
Cc: users at mapguide.osgeo.org
Subject: RE: MapGuide OS with Google Earth

Hi,

I have tried your sample for Google Earth, and it work fine with the
sheybogan sample data.

If I paste this in my internet Explorer
http://localhost/sites/google_earth\water.php
<http://localhost/sites/google_earth/water.php>  I will get a bunch of
coordinates.

But when I try to use my own data I get an error:

PHP Fatal error: Uncaught exception 'mgobjectnotfoundexception' in
Unknown on line 0

In the water.php file I change this line like so:

$featureReader = $featureService->SelectFeatures(new
MgResourceIdentifier("Library://Bolsward/Data/Data/totaal_tvg32010101_v.
FeatureSource"), "totaal_tvg32010101_v", null);

As you can see in XML below, this does exist.  Do you might know why I
don't get anything ?

Thanks,

Willem

<ResourceId>Library://Bolsward/Data/Data/totaal_tvg32010101_v.FeatureSou
rce</ResourceId> 

  <Depth>4</Depth> 

  <Owner>Administrator</Owner> 

  <CreatedDate>2006-04-07T08:32:36Z</CreatedDate> 

  <ModifiedDate>2006-04-07T08:32:36Z</ModifiedDate> 

-
<http://localhost/mapguide/mapagent/mapagent.fcgi?OPERATION=ENUMERATERES
OURCES&VERSION=1.0.0&LOCALE=en&RESOURCEID=Library%3A%2F%2F&TYPE=&DEPTH=-
1##>  <ResourceDocumentHeader
xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:noNamespaceSchemaLocation="ResourceDocumentHeader-1.0.0.xsd">

-
<http://localhost/mapguide/mapagent/mapagent.fcgi?OPERATION=ENUMERATERES
OURCES&VERSION=1.0.0&LOCALE=en&RESOURCEID=Library%3A%2F%2F&TYPE=&DEPTH=-
1##>  <General>

  <IconName>FeatureSourceSdf</IconName> 

  </General>

-
<http://localhost/mapguide/mapagent/mapagent.fcgi?OPERATION=ENUMERATERES
OURCES&VERSION=1.0.0&LOCALE=en&RESOURCEID=Library%3A%2F%2F&TYPE=&DEPTH=-
1##>  <Security
xsi:noNamespaceSchemaLocation="ResourceSecurity-1.0.0.xsd">

  <Inherited>true</Inherited> 

-
<http://localhost/mapguide/mapagent/mapagent.fcgi?OPERATION=ENUMERATERES
OURCES&VERSION=1.0.0&LOCALE=en&RESOURCEID=Library%3A%2F%2F&TYPE=&DEPTH=-
1##>  <Groups>

-
<http://localhost/mapguide/mapagent/mapagent.fcgi?OPERATION=ENUMERATERES
OURCES&VERSION=1.0.0&LOCALE=en&RESOURCEID=Library%3A%2F%2F&TYPE=&DEPTH=-
1##>  <Group>

  <Name>Everyone</Name> 

  <Permissions>r,w</Permissions> 

  </Group>

  </Groups>

  </Security>

  </ResourceDocumentHeader>

  </ResourceDocument>

________________________________

Van: Jason Birch [mailto:Jason.Birch at nanaimo.ca] 
Verzonden: dinsdag 14 maart 2006 8:19
Aan: users at mapguide.osgeo.org
Onderwerp: MapGuide OS with Google Earth

I've uploaded a pretty basic example of using MapGuide OS to serve KML
to Google Earth, based on an example that Bob Bray provided with the
first preview:

http://www.jasonbirch.com/files/google_earth.zip

This is totally unsupported, but in my experience it works with the
Sheboygan data set.  On a standard Windows/Apache/Php install you should
just have to follow the instructions in the readme.txt file.

I had a better example that worked to return data for the current
bounding box (you can see it in action at http://earth.nanaimo.ca/ ) but
I was unable to get this working with the sample data, so either
something has changed with 1.0 or the sample data is different somehow
than what I'm serving.  I didn't get any error messages, but seeing all
of the exception codes in the API, I guess I should be trapping for
these somehow.  Not enough time to research now though.

My to-do list:

- clean up the code, make it more modular, and possibly use TJ's
KMLDocument class for generating the KML:

http://kml.tjworld.net/downloads.php

- figure out how to read the default scale ranges and symbology from
MapGuide, and return a semblance of those instead of having to custom
code each layer.  

- dynamically rewrite the bounding box, so that it shifts to the
foreground when the view is tilted, allowing delivery of data without
killing the server with a huge extent

- deliver GroundOverlay images as an option for small-scale mapping
where serving vectors is inappropriate

Of course Autodesk could just step in any time now and provide a
template for default delivery of KML :)

Jason

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