[ Ø ] Harsh Prakash – GIS Blog

Quiet Musings On Applied Spatial (Health, Disaster, Technology, Planning et al.)

Follow Up [1]: Map Viewer and Google

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A quick note on the happenings at Google: Yesterday, Google added satellite imagery to its mapping. For speedy displays, 256px*256px JPEG image-tiles scanned at different zoom-levels and each weighing around 30 KB, coupled with some nifty AJAX come handy.

Such a drag-and-drool tiling paradigm, although practised for some time now by website developers to load large images, when applied to internet mapping represents a refreshing out-of-the-box approach. The GET HTTP request method uses a cryptic naming convention to fetch these image-tiles from a preexisting pallette, like so:

http://kh.google.com/kh?v=1&t=TILE…

WHERE in one instance, TILE zooms closer from [tqtsqr] to [tqtsqrtssssrq] and still closer to [tqtsqrtssssrtrttr].

Unlike for its regular mapping where Google predictably uses GIF image-tiles each sized at 128px*128px, for its satellite imagery, Google’s preference for JPEG over another competitive format PNG, is worthy of a second glance: As is common knowledge, JPEG supports millions of colors, but is infamous for its lossy compression. PNG on the other hand, is lossless while supporting millions of colors. However, PNG is currently not supported by all browsers and depending on compression settings, may end-up weighing more.

–π

- [ Ø ]

    Written by Harsh

    April 5th, 2005 at 7:29 pm

    Posted in GIS,Mashup

    Tagged with ,

    One Response to 'Follow Up [1]: Map Viewer and Google'

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    1. adobe should make moves into the gis industry. now.

      chris3495

      6 Apr 05 at 8:28 PM

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