[Geomoose-users] using Google layers as background

John Callahan john.callahan at udel.edu
Fri Apr 15 17:01:29 EDT 2011

Thanks Brent.  EPSG:3875 it is.  So the map-source projection parameter in
the mapbook file is for warping the mapserver output to fit the display
coordinates.  Is that correct?  I agree that the server should output maps
in the srs requested and not allow any client-side reprojection.  All of my
WMS services support both my local srs and the various google flavors.

I was looking at both the the GeoMoose demos and noticed in the web mercator
demo, services such as identify and select are not present.  Will those
types of services not work with web mercator?

- John

John Callahan, Research Scientist
Delaware Geological Survey
University of Delaware
URL: http://www.dgs.udel.edu

On Fri, Apr 15, 2011 at 4:48 PM, Brent Fraser <bfraser at geoanalytic.com>wrote:

>  John,
> 1)  Technically they describe the same coordinate system, but 3785 is
> deprecated and replaced by 3875 as the "official" EPSG code.  900913 was the
> original, "user defined" (aka non-offical) code so has been in use longer
> (and some systems may not have adopted the official code yet).  So go with
> 3875 if possible, but you could use 900913 if necessary.
> 2)  You should demand(!) that the WMS servers serve up the data in your
> display coordinate system (it off-loads the re-projection to the servers).,
> but if they don't advertise that they support it, you could get GeoMOOSE to
> warp it on the fly by including a projection='EPSG:4326' option in the
> <map-source> tag.  Be warned that is only does a warp and the layers will
> not line up as you zoom out.  The solution is to set up mapserver to act as
> a WMS client, do the reprojection and serve the result in your coordinates
> system of choice (e.g. 3875).
> 3).  Correct.  And add a PROJECTION block to the LAYER so mapserver knows
> which coordinate system they are in.
> Best Regards,
> Brent Fraser
> On 4/15/2011 1:25 PM, John Callahan wrote:
> I'm creating a GeoMoose application that will use the various Google tile
> layers as backgrounds.  (I originally created a basic app in my local state
> plane projection but then realized that the Google-like backgrounds are
> critical.)   I've downloaded the Web Mercator demo and am looking at
> http://geomoose.org/howto/commercial_layers.html for guidance.  As I go
> through this, a few quick questions:
> 1) Should I use EPSG:3857, EPSG:3785 or EPSG:900913?  Or does it matter as
> long as Proj4 supports it and there's a corresponding file in
> proj4js\lib\defs
> 2) In the mapbook file, should all the data sources (nearly all of WMS
> type) have the same projection attribute, such as projection="EPSG:3857"?
> 3) Just to confirm, my raw data files do not need to be in the "web
> mercator" projection, only the MAP Projection and Extent parameters in the
> map files, correct?
> - John
> ***********************************
> John Callahan, Research Scientist
> Delaware Geological Survey
> University of Delaware
> URL: http://www.dgs.udel.edu
> *******************************
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