Detail displey when zoom in
Bruno Patini Furtado
bpfurtado at GMAIL.COM
Mon Aug 14 10:10:13 EDT 2006
Thanks for the clarification :)
On 8/14/06, Fawcett, David <David.Fawcett at state.mn.us> wrote:
> I would say that zoom is still meaningful in describing MapServer. When
> you 'zoom', you either request a layer that shows more (or less) earth area
> in your fixed-size map window.
> Overviews do not relate directly to the map image being returned by
> MapServer. They are used as part of a raster data source to help make your
> application more efficient. An overview is useful when you have images that
> have a high resolution and you want to use as a data layer on a relatively
> low resolution map.
> For example, if you have an air photo that is 1,000,000 x 1,000,000 pixels
> and you want to use it at full extent in your map image that is 100 x 100
> pixels. Every time that you request a map image, MapServer or one of it's
> components has to look at the big image and figure out what color to make
> each of the pixels in the 100 x 100 pixel layer. That takes a lot of
> Instead, you can pre-build overviews, either inside or outside of the
> image file for your data layer. That way, when you request a map image like
> above, MapServer (or OGR) can decide to just use the pre-built overview.
> -----Original Message-----
> *From:* UMN MapServer Users List [mailto:MAPSERVER-USERS at LISTS.UMN.EDU] *On
> Behalf Of *Bruno Patini Furtado
> *Sent:* Monday, August 14, 2006 7:50 AM
> *To:* MAPSERVER-USERS at LISTS.UMN.EDU
> *Subject:* Re: [UMN_MAPSERVER-USERS] Detail displey when zoom in
> One thing that might help is knowing that the MapServer terminology for
> zoom is Overviews as can be seen in http://mapserver.gis.umn.edu/docs/howto/raster_data/#building-internal-overviews
> Also, the GDAL uses the same term in http://www.gdal.org/gdaladdo.htmlwhere:
> The gdaladdo utility can be used to build or rebuild overview images for
> most supported file formats with one over several downsampling algorithms.
> On 8/13/06, Hooi <wchoonhooi at gmail.com> wrote:
> > I intend to do something like Google Local where when user zoom in, he
> > can see same area but more details. How can I achieve this in Mapserver?
> "Minds are like parachutes, they work best when open."
> Bruno Patini Furtado
> Software Developer
> webpage: http://bpfurtado.net
> software development blog: http://bpfurtado.livejournal.com
"Minds are like parachutes, they work best when open."
Bruno Patini Furtado
software development blog: http://bpfurtado.livejournal.com
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