

Reprojected Zoomable Raster Tiles - mbostock
http://www.jasondavies.com/maps/raster/

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mbostock
Jason’s work here is so exciting because it demonstrates another path to
escape the tyranny of Mercator’s projection. Using reprojection on the client,
you can take any Mercator tile source (that’s nearly all of them) and refit it
to a projection more appropriate for your application. For example, Alber’s
conic projection is equal-area, which is a good choice for choropleths.

In effect, client-based reprojection gives you the convenience of multi-
resolution tiled geospatial data without being beholden to a specific
projection. This is huge.

For a visual explanation: <http://www.jasondavies.com/maps/tile/>

For an example with vector tiles (may fall over under load, YMMV):
<http://www.jasondavies.com/maps/us-rivers/>

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natevw
Years ago I wrestled against similar problems trying to make a completely
visual map-based photo organizer, with only partial success:
<http://calftrail.com/mercatalog.html>

So I can tell you that what Jason Davies has been doing in this realm recently
is 1) really hard, 2) really legit and 3) really exciting. While Mercator was
a great choice for tile maps due to its local properties, at medium and global
scales it'd rarely be one's first choice.

Now, it doesn't have to be.

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cscheid
Awesome work, as usual!

I guess the next feature would be to remap the UI interaction to
transformation of the projection, and not just the 2D window. For example,
Albers' projection includes a latitude and longitude 'center'. So it would be
better to change the latitude and longitude instead of the 2D window into the
static projection. This would minimize the distortion when away from the
natural projection center. The mercator doesn't have a natural center
precisely because it's conformal, but other projections do.

If you already have the projection functions and their inverses, using
automatic differentiation is the obvious choice. I think it might be simply a
matter of computing the inverse projection's change in longitude and latitude
respect to dx and dy, in pixels. That will give you the right numbers, for
very little effort.

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cwmma
Seriously, this is awesome, most of my data and paper maps is in a local
projection, Massachusetts State Plane, super easy to extend this to that.

<http://bl.ocks.org/calvinmetcalf/5629742>

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jasondavies
Just added another example showing raster tiles reprojected using the
satellite projection:

<http://www.jasondavies.com/maps/raster/satellite/>

Unfortunately zooming is not supported for this one due to issues with
distortion, but it's something I'd like to fix.

And another (zoomable Mollweide watercolour):

<http://www.jasondavies.com/maps/raster/mollweide/>

