RE: [OpenMap Users] Moving the map like Google

From: Jay D. Askren <jda_at_quantumleap.us>
Date: Thu, 10 Apr 2008 10:39:35 -0400

I would be very interested in that code if you could post it somewhere.
I've been wanting to do the first item you mentioned but haven't had a
chance to do it.

Jay


-----Original Message-----
From: owner-openmap-users_at_bbn.com [mailto:owner-openmap-users_at_bbn.com]
On Behalf Of Weisburd, Ben
Sent: Thursday, April 10, 2008 10:12 AM
To: 'F.Bayliss'; openmap-users_at_bbn.com
Subject: RE: [OpenMap Users] Moving the map like Google

Hi Frank,

We are doing something similar for a weather display of the continental
US. It has to display large rasters of radar data and various overlays.
We did several optimizations to make google-like panning/zooming work
faster:
- Since the data was on the local disk, we made the map repaint once
when all layers are done rendering, and prevented the layers from
calling repaint() on themselves. This made interaction smoother and
avoided flicker.
- originally we used OMGraphics for the overlays, but this was slow
because they had to project themselves from lat/lon to pixel coordinates
every time the user panned or zoomed. Since we only needed to look at
the continental US, and had a fixed projection type, we treated the map
as a 2D grid with 0,0 being near Seattle. So we made OMGraphics store
everything in our grid's pixel coordinates instead of lat/lon.
- for the large raster images, we pre-generated tiles at several zoom
steps.

We had to do a lot of subclassing for this, but didn't have to modify
openmap source. Let me know if you want any of that code.

-Ben


-----Original Message-----
From: owner-openmap-users_at_bbn.com [mailto:owner-openmap-users_at_bbn.com]
On Behalf Of F.Bayliss
Sent: Thursday, April 10, 2008 6:12 AM
To: openmap-users_at_bbn.com
Subject: [OpenMap Users] Moving the map like Google

Hello,

I've been asked by my upper management to once again mimic the way
Google allows the user to move the map. I've spent a lot of time on
this, too much, and I don't see anyway it can work. I have several,
several layers and the time it takes to process and draw a map movement
event is slow and that results in a choppy map picture. I've tried
several approaches, the best being drawing the map to an image buffer
and replacing the map with that, letting them move what they think is
the map. But this isn't acceptable because it takes time to create the
image. I was hoping the experts had a better idea.

Thanks
Frank

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Received on Thu Apr 10 2008 - 10:42:43 EDT

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