G'Day all,
Sorry to start with a basic context problem, but I don't seem to be able to get myself oriented by reading the OpenLayers docos.
Here's the quick version of the problem:
- We already have a full Geoserver (and GeoNetwork) installation. And we're busy loading data layers into GeoServer and creating metadata in GeoNetwork. So that's going fine.
But the GeoNetwork interface is basically a very geeky catalog. What we need is a very simple/clean map viewer/explorer. I'm trying to set up a single View on OpenLayers to provide this.
- There are about 20 important layers that we'd like users to be able to turn on/off, and there are about 4 different baselayers that would be useful.
All of the layers (baselayers and overlays) are available via WMS (either from our own GeoServer install or from a national agency's WMS)
I have defined the a few of the 20 overlay layers using the [Layers] tab, so they should be available for addition to the map display.
- So the approach we've used is to establish a Preset called Atlas. I expect to define which Base layers and which Overlay layers will be available.
Defining the Atlas Preset...the first snag I hit is the question of projection. The instructions point out that most base layers are 900913, and this is what Google Maps et al provide by default. The Display Projection is set to 4326, which I leave set.
Now I want to add layers...but they are not available in the Overlay selector pane. When the Map Projection is set to 4326, all the base layers are lost, but we get all the overlay layers available.
So: daft question.....how is this supposed to work?
I can't re-project Google's 900913 baselayer, and all my overlays are 4326 (as noted by the instructions).
Is it not possible to get these two projections on top of each other?
It seems like I have to re-project all my overlays to 900913 in order to get them to appear in the Overlays selector...and that just doesn't seem right.
What am I missing?
Thanks in advance!
Comments
I can't re-project Google's
Yes; this is how the OpenLayers module intends to work. Image-based layers (WMS, Google, any other commercial provider) cannot be reprojected in-browser, since that would require the browser to both do complex math quickly, and to warp images, neither of which are possible. Same thing with Drupal; PHP's image processing is not usable for the purpose.
So, all image-based layers need to be in the same projection. Reproject your overlays to 900913 if you want to use Google Maps, or use a 4326 baselayer (there are a few; no attractive ones) if you don't want to reproject your overlays.