Google maps w/ satellite imagery

[Ed McNierney]

Mike -

Well, TopoZone is a MapServer user who STOPPED using tiled imagery
several years ago.  We went the other way, from a pre-tiled proprietary
map image server to using pretty plain vanilla MapServer maps.

It all depends on the application.  What I'll call "TerraServer-style"
tiled images (since they're the first implementation I know of, in 1998)
are fast, and they provide good incremental drawing feedback - you know
something's happening because you see the image appear in pieces.

To get that, you give up arbitrary zoom scales (they're all precomputed)
and you give up the ability to center the map on any point.  DHTML has
fixed the latter problem at the cost of some wasted bandwidth, since
you're downloading images you don't display and may never display.  The
precomputed tiles also create a data management problem, since you need
to reprocess the imagery when you get updates, and that can be just a
bit tricky.  Depending on your update frequency and size, this may not
be an issue.

Google's approach also wastes a lot of bandwidth downloading data that's
never used.  I do not know if that is related to the fact that I've been
getting lots of broken-link images from Google's "satellite" imagery.

You also don't see any UI on Google to turn those various data layers on
and off, right?  Sure, that could be done the same way, but you need to
balance the precomputing overhead with the degree of user control over
the map rendering.  If you're going to give the user many options for
controlling the map display, and do that with a large geographic area,
it might not be worth it.

As in most things in life, there are tradeoffs.  One of my favorite bits
of professional advice came from a former manager of mine who observed,
"All of your problems are caused by solutions."

        - Ed

Ed McNierney
President and Chief Mapmaker
TopoZone.com / Maps a la carte, Inc.
73 Princeton Street, Suite 305
North Chelmsford, MA  01863
Phone: +1 (978) 251-4242
Fax: +1 (978) 251-1396
ed at topozone.com 

-----Original Message-----
From: UMN MapServer Users List [mailto:MAPSERVER-USERS at LISTS.UMN.EDU] On
Behalf Of Mike Davis
Sent: Wednesday, April 06, 2005 8:25 PM
To: MAPSERVER-USERS at LISTS.UMN.EDU
Subject: Re: [UMN_MAPSERVER-USERS] Google maps w/ satellite imagery

I am curious who on the list has been using an AJAX approach to mapping
with mapserver.

As users of my web applications discover google maps and the speed at
which it delivers imagery, I am starting to hear rumblings about the
performance of our in-house applications.

Tools or techniques to tile imagery and pre-cache on the client would be
especially useful.

-Mike

On Apr 6, 2005 5:20 AM, Fawcett, David <David.Fawcett at state.mn.us>
wrote:
> Perhaps there is an opportunity (formal or informal) at the MUM 2005
for people to show how they have been using an AJAX-esque approach to
MapServer applications.
>
> David Fawcett
> Minnesota Office of Environmental Assistance 
> david.fawcett at moea.state.mn.us 651.215.0200
>
>
> -----Original Message-----
> From: UMN MapServer Users List 
> [mailto:MAPSERVER-USERS at LISTS.UMN.EDU]On
> Behalf Of Pascoe,Tim [Burlington]
> Sent: Wednesday, April 06, 2005 8:01 AM
> To: MAPSERVER-USERS at LISTS.UMN.EDU
> Subject: Re: [UMN_MAPSERVER-USERS] Google maps w/ satellite imagery
>
> Take a look at:
>
> http://adaptivepath.com/publications/essays/archives/000385.php
>
> I believe this is the technology behind the Google Maps interface.
>
> Tim
>
> -----Original Message-----
> From: UMN MapServer Users List [mailto:MAPSERVER-USERS at lists.umn.edu] 
> On Behalf Of Charlton Purvis
> Sent: April 6, 2005 8:18 AM
> To: MAPSERVER-USERS at lists.umn.edu
> Subject: [UMN_MAPSERVER-USERS] Google maps w/ satellite imagery
>
> For those of you who haven't seen it, you're missing out.
> http://maps.google.com has satellite imagery that performs 
> spectacularly.
> Enter an address; the satellite option is a link in the upper RH 
> corner of that page.
>
> Even the dingbat public is tuned in to the site, 
> http://www.cnn.com/2005/TECH/internet/04/05/google.maps.ap/index.html.
>
> Charlton
>