[mapserver-users] Image Speed Questions---Generic

[Stephen Lime]

Hi Lowell: Option 1 sucks so don't even consider that. I've used 2 stratagies
here, the image catalog and single images at multiple resolution. Both certainly
have their place and work well under the right circumstances. We serve USGS
DRGs and DOQs for the entire state (~1200 tiles) using tiled GeoTIFFs. Works
great as long as you display at appropriate scales which isn't much of an issue
with those datasets since they're only useful over a limited number of scales. The
DOQ dataset is about 20Gb, the 3 DRG datasets are about 6Gb.

We also have a LandSat TM mosaic. We serve those using a pyramid type system
where each reduced resolution image is a layer tied to a scale range. Finally there
are the source images that are handled using tiling.

Neither LizardTech nor ERMapper (ECW) are forthcoming with anything but Windows
APIs so don't look for support there. The ERMapper folks do have a demo out there
that uses MapServer on top of their imagery using a plugin they developed. Perhaps
JPEG2000 will be ready soon.

Steve

Stephen Lime
Internet Applications Analyst

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

>>> "Ballard,Lowell" <LBallard at YesVirginia.org> 07/26/01 12:15PM >>>
Say, for example, you needed to display/serve high-res imagery (on the
Internet) for a large spatial extent (e.g., a state or region).  There would
be several ways to get this done.  

For example:

1. You could use multiple images and reference each as an individual layer
(administrative nightmare).

2. You could use multiple images and get at them through an image catalog.

3. You could mosaic them into one large image (could get REALLY big
fast--probably not feasible)

4.  If pyramid layers/aux/MrSid were supported you use them to display
moderate sized mosaics or original imagery (greatly reduce storage footprint
but uncomressing hammers CPU cycles).

5. You could resample imagery at different resolutions (1m pixel resolution;
5m; 10m) and reference each collection (e.g., 5m) with a different image
catalog depending on viewing scale (i.e., viewing at county-extent use 10m
catalog; city-level use 5m; subdivision use 1m).

6.  You store them all in SDE (~2:1 compression lossless).

7. About any combination of the above (e.g., resample imagery to 1m, 5m etc
and create pyramids for those).

8. .......

I'm curious how others would accomplish/approach this task.  I can post a
summary.

Thanks,

Lowell Ballard