[mapserver-dev] Use tile index instead of raster geometry

Bill Thorp bill3000 at gmail.com
Sun May 29 06:19:03 PDT 2016

> Please detail the steps you undertook, what result you were expecting, and
> what you got instead.

I'll explain in greater detail...  [Please ignore the similarities in my
test case to potential tile cache solutions.  Tile cache solutions will not
work for me.]

I took two simple 512x512 JPEGs, one visualizing the earth's left
hemisphere, one the right.  I created JGW world files for each JPG by hand,
so that both were correctly positioned using decimal degrees.  I then ran
gdaltindex on the data to create a .SHP tile index.  I used MapManager to
create a MapServer .map file, and added the tile index to the map.  I was
able to see both JPEG hemispheres forming a complete image.  I then deleted
the JGW world files, and attempted to view my map again.  Only one image
appeared, and it was much larger than before.  I interpreted this as
meaning that both images were drawn with any affine transformation, one on
top of the other.  This is the expected behavior, of course, if I had
simply added two images without a world files nor tile index.

My preference would have been that MapServer provide an option to override
the geometries defined within each file, instead using the geometry listed
in the tile index.  This would of course mean that my tile index would have
to be generated through means other than the gdaltindex tool.

Left Hemisphere JGW

Left Hemisphere Tile Index Geometry
  location (String) = 0.jpg
  POLYGON ((-180 90,0 90,0 -90,-180 -90,-180 90))

Right Hemisphere JGW

Right Hemisphere Tile Index Geometry
  location (String) = 1.jpg
  POLYGON ((0 90,180 90,180 -90,0 -90,0 90))

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