Comments on: Switching between mapping APIs and universal zoom levels http://code.davidjanes.com/blog/2008/11/08/switching-between-mapping-apis-and-universal-map-levels/ Fri, 03 Feb 2012 00:50:35 +0000 hourly 1 http://wordpress.org/?v=3.2.1 By: Klokan Petr Pridal http://code.davidjanes.com/blog/2008/11/08/switching-between-mapping-apis-and-universal-map-levels/#comment-106 Klokan Petr Pridal Tue, 19 May 2009 14:44:18 +0000 http://code.davidjanes.com/blog/?p=152#comment-106 Hi, I just would like to mention here the mashup for tile coordinates detection: http://www.maptiler.org/google-maps-coordinates-tile-bounds-projection/ You can search a place, or zoom&pan to it and you will see directly the coordinates of the tiles and bounds in several systems. On the website is also the Python module (open-source) for calculating and conversion of all the systems... Hi,

I just would like to mention here the mashup for tile coordinates detection:

http://www.maptiler.org/google-maps-coordinates-tile-bounds-projection/

You can search a place, or zoom&pan to it and you will see directly the coordinates of the tiles and bounds in several systems.

On the website is also the Python module (open-source) for calculating and conversion of all the systems…

]]> By: Shivaji http://code.davidjanes.com/blog/2008/11/08/switching-between-mapping-apis-and-universal-map-levels/#comment-105 Shivaji Tue, 16 Dec 2008 10:39:23 +0000 http://code.davidjanes.com/blog/?p=152#comment-105 Hi, I need to take a road and buildings all the shapes is that possible for me. And i need all this things are need in SHP files thanks. Hi, I need to take a road and buildings all the shapes is that possible for me.
And i need all this things are need in SHP files
thanks.

]]> By: David Janes’ Code Weblog » Once more with the maps http://code.davidjanes.com/blog/2008/11/08/switching-between-mapping-apis-and-universal-map-levels/#comment-104 David Janes’ Code Weblog » Once more with the maps Sun, 07 Dec 2008 12:48:43 +0000 http://code.davidjanes.com/blog/?p=152#comment-104 [...] Migurski added a very informative comment about tiling levels here, with a pointer to way more detailed information [...] [...] Migurski added a very informative comment about tiling levels here, with a pointer to way more detailed information [...]

]]> By: David Janes http://code.davidjanes.com/blog/2008/11/08/switching-between-mapping-apis-and-universal-map-levels/#comment-103 David Janes Sun, 07 Dec 2008 12:11:03 +0000 http://code.davidjanes.com/blog/?p=152#comment-103 Thanks Michal. And then Askimet ate it, sorry for taking so long to get it up here! Thanks Michal. And then Askimet ate it, sorry for taking so long to get it up here!

]]> By: Michal Migurski http://code.davidjanes.com/blog/2008/11/08/switching-between-mapping-apis-and-universal-map-levels/#comment-102 Michal Migurski Tue, 02 Dec 2008 21:52:29 +0000 http://code.davidjanes.com/blog/?p=152#comment-102 (I just wrote a lengthier version of this comment, then my browser ate it. rewriting, sad.) Eugene's right on the mark with his explanation. We did a bunch of this same exploration about two years ago with Modest Maps, summarized here: http://modestmaps.mapstraction.com/trac/wiki/TileCoordinateComparisons An additional convenience of the scheme used by Google & VEarth gets you is the ability to use simple arithmetic in your exponents with your map code. With the furthest-out zoom level equal to zero, you can easily determine how many tiles your complete map contains at each zoom, and rapidly convert between them. For example, at zoom level zero, 2^0 = 1 tiles across to cover the whole world; at zoom level one, 2^1 = 2 tiles across to cover the whole world; at zoom level two, 2^2 = 4 tiles across to cover the whole world, etc. Yahoo's choice of numbering scheme makes probably the least sense of all, because they've given themselves an implied maximum zoom. The Modest Maps python branch has some of the most succinct bits of code & math for dealing with this: http://modestmaps.mapstraction.com/trac/browser/trunk/py/ModestMaps/Tiles.py http://modestmaps.mapstraction.com/trac/browser/trunk/py/ModestMaps/Google.py http://modestmaps.mapstraction.com/trac/browser/trunk/py/ModestMaps/Microsoft.py http://modestmaps.mapstraction.com/trac/browser/trunk/py/ModestMaps/Core.py#L43 (I just wrote a lengthier version of this comment, then my browser ate it. rewriting, sad.)

Eugene’s right on the mark with his explanation. We did a bunch of this same exploration about two years ago with Modest Maps, summarized here:
http://modestmaps.mapstraction.com/trac/wiki/TileCoordinateComparisons

An additional convenience of the scheme used by Google & VEarth gets you is the ability to use simple arithmetic in your exponents with your map code. With the furthest-out zoom level equal to zero, you can easily determine how many tiles your complete map contains at each zoom, and rapidly convert between them. For example, at zoom level zero, 2^0 = 1 tiles across to cover the whole world; at zoom level one, 2^1 = 2 tiles across to cover the whole world; at zoom level two, 2^2 = 4 tiles across to cover the whole world, etc.

Yahoo’s choice of numbering scheme makes probably the least sense of all, because they’ve given themselves an implied maximum zoom.

The Modest Maps python branch has some of the most succinct bits of code & math for dealing with this:
http://modestmaps.mapstraction.com/trac/browser/trunk/py/ModestMaps/Tiles.py
http://modestmaps.mapstraction.com/trac/browser/trunk/py/ModestMaps/Google.py
http://modestmaps.mapstraction.com/trac/browser/trunk/py/ModestMaps/Microsoft.py
http://modestmaps.mapstraction.com/trac/browser/trunk/py/ModestMaps/Core.py#L43

]]> By: Stefan Knecht http://code.davidjanes.com/blog/2008/11/08/switching-between-mapping-apis-and-universal-map-levels/#comment-101 Stefan Knecht Tue, 02 Dec 2008 19:02:05 +0000 http://code.davidjanes.com/blog/?p=152#comment-101 What a marvellous article -- will crosspost & comment with full kudos! What a marvellous article — will crosspost & comment with full kudos!

]]> By: Eugene http://code.davidjanes.com/blog/2008/11/08/switching-between-mapping-apis-and-universal-map-levels/#comment-100 Eugene Tue, 02 Dec 2008 16:57:17 +0000 http://code.davidjanes.com/blog/?p=152#comment-100 It's extremely likely that Microsoft and Yahoo! followed Google's lead here. But the derivation is actually quite logical. The first ingredient is the Mercator projection, which is the best projection suited for slippy maps like these since it preserves shape and angles. (Google once used a plate caree projection for the satellite maps but quickly abandoned it because circles became ellipses far from the equator.) The second ingredient is using a quad-tile implementation with 256-pixel-width map tiles; it's also quite convenient that a square cut of the Mercator projection of the world spans from ~85°S to ~85°N, which covers most of the places most people would be interested at (too bad for the poles). What's not logical is the fact that Google uses a spherical approximation of the WGS84 datum (which is actually not too inaccurate) for computational efficiency. The question is whether Microsoft and Yahoo! also uses this spherical approximation. If not, there will be places on the three maps that will be off. It's been confirmed over at http://cfis.savagexi.com/2006/05/03/google-maps-deconstructed that Microsoft also uses a spherical approximation. Yahoo is likely doing the same thing. It’s extremely likely that Microsoft and Yahoo! followed Google’s lead here. But the derivation is actually quite logical. The first ingredient is the Mercator projection, which is the best projection suited for slippy maps like these since it preserves shape and angles. (Google once used a plate caree projection for the satellite maps but quickly abandoned it because circles became ellipses far from the equator.) The second ingredient is using a quad-tile implementation with 256-pixel-width map tiles; it’s also quite convenient that a square cut of the Mercator projection of the world spans from ~85°S to ~85°N, which covers most of the places most people would be interested at (too bad for the poles).

What’s not logical is the fact that Google uses a spherical approximation of the WGS84 datum (which is actually not too inaccurate) for computational efficiency. The question is whether Microsoft and Yahoo! also uses this spherical approximation. If not, there will be places on the three maps that will be off. It’s been confirmed over at http://cfis.savagexi.com/2006/05/03/google-maps-deconstructed that Microsoft also uses a spherical approximation. Yahoo is likely doing the same thing.

]]> By: Online Maps Share Same Zoom Levels | Maps & Atlas http://code.davidjanes.com/blog/2008/11/08/switching-between-mapping-apis-and-universal-map-levels/#comment-99 Online Maps Share Same Zoom Levels | Maps & Atlas Tue, 02 Dec 2008 06:06:24 +0000 http://code.davidjanes.com/blog/?p=152#comment-99 [...] David Janes: “Did you know that Google Maps, Yahoo Maps and Virtual Earth all use the same map tile resolutions? That is, you can actually seamlessly switch between mapping systems and have everything line up exactly the same way.” Examples provided. Google has one wider zoom than the others; Yahoo lacks the two closest levels of Google and Virtual Earth. Via Global Nerdy. [...] [...] David Janes: “Did you know that Google Maps, Yahoo Maps and Virtual Earth all use the same map tile resolutions? That is, you can actually seamlessly switch between mapping systems and have everything line up exactly the same way.” Examples provided. Google has one wider zoom than the others; Yahoo lacks the two closest levels of Google and Virtual Earth. Via Global Nerdy. [...]

]]> By: Craig Dunn http://code.davidjanes.com/blog/2008/11/08/switching-between-mapping-apis-and-universal-map-levels/#comment-98 Craig Dunn Mon, 01 Dec 2008 20:51:24 +0000 http://code.davidjanes.com/blog/?p=152#comment-98 Cool post - I've often wondered whether this was just coincidence or some sort of 'standardisation' (or a function of sources/providers of the imagery and maps). The same is true of OpenStreetMap tiles, and the 'overlays' used by Google (for streets & streetview) and Yahoo. Google Moon & Mars also use the same tile system, but with fewer zoom levels (6 or 7). In other countries (ie. outside the USA) the 'lowest' zoom level varies as they don't always have high-resolution imagery for each country (and across the oceans). You can play interactively at http://silverlightearth.com/2/ (although due occasional updates by the tile servers some selections occasionally won't load). For example, you can overlay Googles 'blue glow' streetview indicator over OpenStreetMap or overlay Googles roads over Virtual Earth's or NASAs satellite imagery... http://conceptdev.blogspot.com/2008/08/silverlightearth-gets-openstreetview.html Cool post – I’ve often wondered whether this was just coincidence or some sort of ‘standardisation’ (or a function of sources/providers of the imagery and maps).

The same is true of OpenStreetMap tiles, and the ‘overlays’ used by Google (for streets & streetview) and Yahoo. Google Moon & Mars also use the same tile system, but with fewer zoom levels (6 or 7). In other countries (ie. outside the USA) the ‘lowest’ zoom level varies as they don’t always have high-resolution imagery for each country (and across the oceans).

You can play interactively at http://silverlightearth.com/2/ (although due occasional updates by the tile servers some selections occasionally won’t load). For example, you can overlay Googles ‘blue glow’ streetview indicator over OpenStreetMap or overlay Googles roads over Virtual Earth’s or NASAs satellite imagery…
http://conceptdev.blogspot.com/2008/08/silverlightearth-gets-openstreetview.html

]]> By: Universal Zoom Levels for Google Maps, Live Search Maps and Yahoo! Maps http://code.davidjanes.com/blog/2008/11/08/switching-between-mapping-apis-and-universal-map-levels/#comment-97 Universal Zoom Levels for Google Maps, Live Search Maps and Yahoo! Maps Sun, 09 Nov 2008 15:13:53 +0000 http://code.davidjanes.com/blog/?p=152#comment-97 [...] article Switching Between Mapping APIs and Universal Zoom Levels at David Janes’ Code Weblog explains that the mapping systems differ in their zoom [...] [...] article Switching Between Mapping APIs and Universal Zoom Levels at David Janes’ Code Weblog explains that the mapping systems differ in their zoom [...]

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