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Non-standard tile sizes and Euclidean projections.

Dec 23, 2008 at 3:59 AM

I'm very interested in converting an existing mapping project that I and a few colleagues have created over to DeepEarth from a Google Maps based map.

There are a few issues though and they are:
  1. We do not use 256x256 tiles.  We currently use 320x320 tiles because of technical reasons.  I was looking at Deep Zoom and it apparently uses 256x256 tiles.  Is it possible to use tiles that aren't the standard, but still square?
  2. Is it possible to make it work with projections besides Mercator?  We currently use a Euclidean (the world we are mapping is flat) projection.  Is it possible to use a projection not associated with general geography?
Any responses would be greatly appreciated!


Joshua R.
Dec 23, 2008 at 6:31 AM
Deep Zoom, specifically the MSI control can accept different tile sizes and even an overlap.
Now we did start down the track of allowing any tile size but every data source we used and all the tile making tools were 256px.

In our BaseLayer class you will see we have this defaulted to 256px, you can override this for your new base layer, but I must admit I havn't tested it with anything but 256px.
The good news is this project is open source so if you're really keen, download the source and see what is needed. If there are some small changes needed post them here and I'll make sure it happens. Our focus for the next release is on Geometry and drawing tools so we won't be looking into this in the next few weeks.
Dec 23, 2008 at 8:29 AM
Thanks for the information on the tiles.  I will definitely look into making it work with our tile sizes.  We had tried 256x256 tiles, but we actually wound up with more images overall taking up more disk space.  The tiles at the edge of the area being mapped were also only partially covered, so we had a substantial amount of wasted disk space to account for those edge tiles.

Any information on projections, would be appreciated.
Dec 23, 2008 at 7:01 PM
I'll like to report that DeepEarth definitely works with non-standard tile sizes.  The 320x320 tiles are working great with DeepEarth.  Just working on changing the projection so that coordinates appear correctly.
Dec 23, 2008 at 10:07 PM
Thats great! Yes with the projection again we did try to set it up in  way that it could be changed, but we only ever needed mecator and clearly you can't mix projections as we have no way to do tranforms on layers in the MSI.
Again please do let us know if their are some changes we should make to accomidate what you need, we will be added all sorts of functionlaity in the comming months.
Dec 23, 2008 at 11:26 PM
Could you also let us know what changes you made (either briefly or in detail) so we know what to change on our end for better interoperability with different size tiles. Thanks and great job!
Dec 24, 2008 at 3:50 AM
Overriding the projection for the map was actually rather simple.  Much simpler than that Google Maps API, for my purposes.  I just derived from IProjection.

As for allowing 320x320 tile sizes, I changed DefaultTileSize in BaseLayer to protected, so it could be overridden in derived classes.  There's probably a better way to do it, my change was just the simplest, quickest hack I could think of for the time being.  Overriding the value to 320 was all I had to do get it working with DeepEarth.

I want to thank you all for your great work on DeepEarth!  I've considered rewriting this project in Silverlight for quite sometime, and your work just made it much easier to work with.