[mapserver-users] Split large tiffs (topos) like TopoZone

[Stephen Lime]

Ok, dug out the old script (see attached). It basically uses a layer definition
for a tiled raster layer (e.g. DRGs) to create the small images. What you end
up doing is laying a grid across the state and are using MapServer to render
a map for each grid cell. The script stores images in the same row together
in a directory. One by product of the script is a shapefile that stores each
image location and name. It could be used with MapServer itself but I've 
never done that in practice. It was used more for validation. Since we're
laying a rectangular grid over a irregularly shaped state the script checks
for empty images and deletes them. The server-side script compensates
for the missing data. I ran the gentiles.pl script for each of the DRG layers I
have here. The settings in the attached script are for the 1:24k dataset.

The script generates maps at a single resolution. The cellsize I use comes
from the raw DRGS and gives us output images that show every pixel in
the dataset.

Steve

Stephen Lime
Data & Applications Manager

Minnesota DNR
500 Lafayette Road
St. Paul, MN 55155
651-297-2937

>>> Daniel Ems <dems at terra.sdimaps.com> 10/19/01 07:36AM >>>

On Fri, 19 Oct 2001, Stephen Lime wrote:

> Ed is quite correct (he should be, it's his site). I did the same
> thing for Minnesota (maps.dnr.state.mn.us/tomo, ~300,000 images) and
> it works very well. That script is simple perl script that doesn't use
> MapServer. However, I did use perl and MapScript to compute the 300k
> images (I think I still have the script if anyone want to take a
> look). Took a day. Can MapServer and the TOMO server work together?
^^^^^^^^^^
^^^^^^^^^^ I'd like a look!


> Possibly but you'd be bound by the non-MapServer application because
> of the nature of the underlying data.
>
> Again, TOMO and TopoZone are built to serve one layer very fast, but
> I've been using the exact same datasets (quad-based DRGs) that the
> little images were computed from in a tiled fashion to support a much
> broader range of scales and applications with great success and by
> managing a few thousand images instead of a few hundred thousand. I
> can only imagine what the TopoZone folks go through with 17 million
> images and all the projection headaches.
>
> Steve
>
> Stephen Lime
> Data & Applications Manager
>

<snip>

Thanks!

-- 
Daniel Ems

AM/FM/GIS Technical Support
Spatial Data Integrations, Inc.


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