Display progress bar while waiting for data

Tue May 24 08:38:49 EDT 2005

You could also prevent your aerial layer from being available at full zoom
out by setting the MAXSCALE property of the aerial layer.

-----Original Message-----
From: Gambin Dejan [mailto:Dejan.Gambin at PULA.HR]
Sent: Tuesday, May 24, 2005 8:29 AM
To: MAPSERVER-USERS at LISTS.UMN.EDU
Subject: Re: [UMN_MAPSERVER-USERS] Display progress bar while waiting for
data

I have just created tileindex with gdaltindex if I remember, that is all. It
is obvious that I have to learn a bit more so thank you very much for
gdaladdo link. I really don't know much about overviews and the other things
you mention but I would really like to get some good directions, links,
literature to start learning.

Thanks very much

Dejan

-----Original Message-----
From: Ed McNierney [mailto:ed at topozone.com]
Sent: Tuesday, May 24, 2005 2:22 PM
To: Gambin Dejan; MAPSERVER-USERS at LISTS.UMN.EDU
Subject: RE: [UMN_MAPSERVER-USERS] Display progress bar while waiting for
data

Dejan -

Have you created "overviews" with GDAL, or created other resampled,
lower-resolution copies of your images to be used when the view is zoomed
out?  That's the first thing you should do, in order to fix the performance
problem rather than try to display an animated advertisement for it!

Look at the gdaladdo documentation to start.  It will let you resample the
images to lower resolution versions ONCE rather than doing it on the fly for
every map request.

     - 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 Gambin Dejan
Sent: Tuesday, May 24, 2005 6:08 AM
To: MAPSERVER-USERS at LISTS.UMN.EDU
Subject: Re: [UMN_MAPSERVER-USERS] Display progress bar while waiting for
data

Thanks everybody participating in the discussion of displaying progress bar.
I am aware of the problem but just want to describe something that is
happening on my site.

I have a set of 18 GeoTIFF ortophoto color images, each one has a size of
80MB. I have created tileindex shapefile to increase performance in reading
the data and I have informed the users they should first have to zoom onto
desired extent on the map and activate the ortophoto layer after that to
speed up the loading. But users are just users and many of them are trying
to activate the ortophoto layer before that (while the map is in full view)
so the loading is slow.

I have put a "Loading" message but the point is the following: when I load
the image on the local network, I get the "Loading" message and I have to
wait about 30 seconds, then the image is displayed at once. On the slow
connection I also get "loading" message displayed about 30 seconds and then
the map is displayed incrementally (that is ok). So my problem is those 30
seconds (that can arise to several minutes regarding the number of
simultaneous users of course). Can I do something?

Thanks, Dejan

-----Original Message-----
From: Ed McNierney [mailto:ed at topozone.com]
Sent: Tuesday, May 17, 2005 6:35 PM
To: Gambin Dejan; MAPSERVER-USERS at LISTS.UMN.EDU
Subject: RE: [UMN_MAPSERVER-USERS] Display progress bar while waiting for
data

Dejan -

I'll second Frank's scepticism here.  Most of the "Image Loading" animations
you see on mapping sites are just that - animations.  They're standalone
animated GIFs and the like which cause pixels to twinkle on the user's
screen but which have no relationship to the actual progress of the
application.  The server could burst into flames and the "Image Loading"
graphic would keep dancing.

The site Regina mentions falls into this category.  IMHO, these kinds of
graphics are primarily used to try to cover up slow map servers, and not to
give users meaningful progress feedback.

I think by far the best feedback mechanism for image load time is the map
image itself.  If you simply display the image in a format that browsers can
easily render incrementally, then the user can see the image begin to appear
and will get a good feel for how long it will take just by watching it.
JPEG is NOT a good choice for this, but GIF and PNG images should render
properly on most browsers.

For example, look at this image:

http://www.topozone.com/images/MtMonadnockTopo.gif

Over a slow connection.  You should see the large map image load
incrementally, so you know things are working.  If the image were smaller
and in a frame (to define the final output size) it would be relatively easy
to assess how much progress is being made.

        - Ed

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

-----Original Message-----
From: UMN MapServer Users List [mailto:MAPSERVER-USERS at LISTS.UMN.EDU] On
Behalf Of Dejan Gambin
Sent: Monday, May 16, 2005 5:06 PM
To: MAPSERVER-USERS at LISTS.UMN.EDU
Subject: [UMN_MAPSERVER-USERS] Display progress bar while waiting for data

Hi,

Is it possible to create some kind of progress bar while waiting for raster
data to be displayed. I have some raster data in GeoTIFF format that some
users with a slow connection must wait for. I am wondering if I can show
them a progress bar indicating "estimated" time they have to wait so they
know and they can wait or cancel the process.

Does anyone have a suggestion on what is the best way to inform users?

thanks very much

dejan