[Mapserver-users] Terra Server WMS

[Dylan Keon]

Ed - great post.

Erich - one downside is that the Terraserver DOQ imagery is JPEG (read: 
24-bit).  So it only looks good if you render it as 24-bit within your 
MapServer app, which means you can end up pushing some pretty large 
images to the user.  What I do is render all output as 8-bit unless the 
DOQ layer is displayed - then I switch to 24-bit.  This keeps images at 
respectable sizes until a DOQ is requested.  I just use a bit of PHP 
MapScript code to do this.

You will need to use MS 4.0 beta along with the latest version of GD to 
get 24-bit capabilities.

The upside is that it saves a lot of disk space, as you mentioned.

--Dylan


Erich Schroeder wrote:
> Thanks Ed, this makes it clear that I'll have to experiment. When I 
> develop things, I'll be dealing with Illinois which spans zones 15 & 16. I 
> have access to a doq set projected into an extended 15 (if I remember 
> right), so I might have to use that. Still, I was liking the idea of using 
> Terraserver if that was possible, thereby saving my disk space.
> 
> Erich
> 
> On Tue, 17 Jun 2003, Ed McNierney wrote:
> 
> 
>>Erich -
>>
>>Yes, but be careful.
>>
>>When you say "spanning two UTM zones", do you mean displaying maps in
>>each of two different zones, or displaying maps that cross the boundary
>>between two UTM zones?
>>
>>Your MAP file (or querystring parameters) will specify the OUTPUT
>>projection of your map.  The PROJECTION blocks in each layer (including
>>the WMS layers) specify the INPUT projection of each data layer.
>>MapServer will automatically reproject the requested output area into
>>the projection of each source layer and select the appropriate data from
>>that layer (if any) and reproject it to the output projection.
>>
>>With Microsoft TerraServer's WMS interface, each UTM zone is served as a
>>WMS layer in its "native" projection.  So if you want data for two
>>adjacent zones, you create two WMS layers, each with the appropriate
>>projection block (the NAD83 UTM EPSG codes are 269xx where the last two
>>digits are the UTM zone number, with a leading zero if needed, as in
>>Dylan's example).
>>
>>HOWEVER, Microsoft TerraServer pads the edge of each UTM zone with
>>"clouds" - their "no-data" imagery.  Here's an example:
>>
>>http://terraserver.microsoft.com/image.aspx?Lon=-72&Lat=43&w=1&ref=G|-72
>>,43
>>
>>This shows a spot at the edge of UTM Zones 18/19.  The projection is UTM
>>Zone 18, and the area to the east of the zone boundary is "clouds".  If
>>you use Microsoft TerraServer's imagery this way, you should realize
>>that you will never see an image that correctly straddles a zone
>>boundary (it's certainly possible - we've done it on TopoZone for years)
>>and that any image that crosses the zone edge will look like this.  If
>>you moved a little east you'd see imagery on the right and clouds on the
>>left.
>>
>>Part of the problem is that the TerraServer WMS service reports this
>>area as "data" and therefore serves an image to you, even though there's
>>no real imagery there.  The WMS interface doesn't seem to add the
>>"clouds" but simply returns a solid white area where there's no data.
>>
>>If it fits your application, you might try using the OFFSITE statement
>>to make the color white transparent in the WMS layers.  This would then
>>allow the layer "underneath" to show through.  You would need to make
>>your map background white, or add a solid white layer underneath the WMS
>>images, in order to allow the REAL white on the images to be displayed.
>>
>>	- Ed
>>
>>Ed McNierney
>>President and Chief Mapmaker
>>TopoZone.com / Maps a la carte, Inc.
>>73 Princeton Street, Suite 305
>>North Chelmsford, MA  01863
>>Phone: (978) 251-4242  Fax: (978) 251-1396
>>ed at topozone.com
>>
>>
>>-----Original Message-----
>>From: Erich Schroeder [mailto:erich at museum.state.il.us] 
>>Sent: Tuesday, June 17, 2003 11:38 AM
>>To: Dylan Keon
>>Cc: mapserver-users at lists.gis.umn.edu
>>Subject: Re: [Mapserver-users] Terra Server WMS
>>
>>On Tue, 17 Jun 2003, Dylan Keon wrote:
>>
>>
>>>   PROJECTION
>>>     "init=epsg:26910" #NAD83 UTM zone 10N
>>>   END
>>
>>This is great! I'll be saving this message for future use!
>>
>>In my case, I would be spanning two utm zones. How would I handle this?
>>Should there be two doq layers, one for each zone, and then the html
>>form
>>turns both on when the user asks for DOQs?
>>
>>Erich
>>
>>
> 
> 

-- 
************************************************
  Dylan Keon
  GIS/Database Specialist
  Northwest Alliance for Computational
  Science and Engineering (NACSE)
  Oregon State University
  Corvallis, OR 97331
  keon at nacse.org        (541) 737-6608
************************************************