[Geomoose-users] Web Mercator

[Len Kne]

Hi Heather
On the quality of the FSA images, check that you are requesting a jpg version from the WMS and that you are serving it from the map file as a jpg or png - look for the IMAGETYPE tag.
The shifting of the non-base map layers is a known issue and a ticket created.  A workaround would be to leave the Google maps layer on and have the WMS image draw over the top of it.  In your case, change the group in the catalog to allow multiple layers or move the WMS out of the group.
I've also seen the problem with measurement error  when using the web Mercator projection.  The error gets worse as you move away from the equator.  Fortunately the error can be somewhat calculated and corrected; I've been working on a script that does this and can share it when it is done...hopefully next week.  The accuracy of measurements in the web Mercator projection will never be that good when at a large scale, a trade off for getting a base map for the entire world.
Len
From: Heather Wirth [mailto:HWIRTH at co.benton.mn.us]
Sent: Friday, April 09, 2010 8:20 AM
To: Len Kne; geomoose-users at lists.sourceforge.net
Subject: Re: [Geomoose-users] Web Mercator

We got the layers to reproject properly, but now have another issue.

The new issue has to do with the LMIC FSA photos.  We reprojected the imagery in a mapfile, and when the page loads, the image is in the correct location, but it looks really bad (see attached LMICFSA.jpg).  Also, when we zoom in, or pan around the map, it doesn't behave as you might expect.  For instance, zooming in on Benton County actually centers the map on the south end of Cass county, and the map does not completely fill the map area in the browser (see attached Browser.jpg).

Finally, we also noticed that the measure distance tool is off.  Measuring a length that should be about 1 mile returns about 1.5 miles.  Is this a units problem, and something we need to change somewhere, or is it a bigger problem?

Thanks again for your help.

Heather

---------------
Heather Wirth
Benton County GIS Specialist
7752 Highway 25 NE, PO Box 247
Foley, MN 56329
Phone: 320-968-5168
Fax: 320-968-5333

>>> Len Kne <lkne at houstoneng.com> 4/6/2010 7:32 AM >>>
Heather
You will want to change the layer type to "mapserver", this will access the data via mapscript instead of making a WMS call to get the data.  If that doesn't fix it, the pink screen usually means that there is an error in the mapfile.  You can track down the problem in Firefox by going to Tools >> Page Info and selecting the media tab.  Find the address that calls the layer in question and copy that address into another Firefox tab and call it.  This should give you an error message to help track down the problem.
Len

From: Heather Wirth [mailto:HWIRTH at co.benton.mn.us]
Sent: Tuesday, April 06, 2010 7:16 AM
To: Len Kne; geomoose-users at lists.sourceforge.net
Subject: Re: [Geomoose-users] Web Mercator

We re-projected the parcel layer that comes with the web mercator download, hoping that if we could get the demo layer to work, we could add other layers.  After making that change, changing the extent in the mapfile (to the "zoom to parcel data" extent from the mapbook), and removing any reference to EPSG 26915 (also tried changing those references to 900913) all we get is the pink screen.

Are we missing something easy?

Also, we noticed in the mapbook's map-source that the parcel layer type is wms; is there a reason to not use the mapserver type?

Thanks for your help.

Heather

>>> Len Kne <lkne at houstoneng.com> 4/5/2010 1:11 PM >>>
Hi Heather
The web Mercator demo re-projects the county boundaries on the client side (that is with GeoMOOSE using OpenLayers).  I've not seen good results re-projecting on the client and can recommend two options:

1.       Re-project the layers will use in GeoMOOSE to the web Mercator projection (in Arc, it is web Mercator (auxiliary sphere)).  This will give the best performance as the layers will not have to be re-projected every time there is a map redraw.

2.       Do the re-projection in the map file.
Len
From: Heather Wirth [mailto:HWIRTH at co.benton.mn.us]
Sent: Monday, April 05, 2010 12:57 PM
To: geomoose-users at lists.sourceforge.net
Subject: [Geomoose-users] Web Mercator

We are just starting to look at the web mercator download and demo, and noticed that there seems to be a problem with how everything lines up.  For instance, if I use the "Jump To" to zoom to the full state of MN, the counties do not line up properly.  Is there a fix for this?  Any help would be much appreciated.

Heather

---------------
Heather Wirth
Benton County GIS Specialist
7752 Highway 25 NE, PO Box 247
Foley, MN 56329
Phone: 320-968-5168
Fax: 320-968-5333
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.osgeo.org/pipermail/geomoose-users/attachments/20100409/01590239/attachment.html