[mapserver-users] Is using ECW format allowed or not?

[Richard Greenwood]

On Mon, Oct 20, 2008 at 11:54 AM, Rahkonen Jukka
<Jukka.Rahkonen at mmmtike.fi> wrote:
> Gregor Mosheh wrote:
>
>>> 1. Can we use our compressed ECW images as input for MapServer WMS?
>>> 2. Can we use ECW as an output format for MapServer WCS?
>
>> The license agreement says that the ECW SDK cannot be used "on a server"
>> then goes on to define that as a computer connected to the Internet
>> which provides images. I'd say that clearly rules out MapServer
>> consuming ECW. Very unfortunate, but in my opinion very clear.
>
>> In my tests, I have found that JPEG2000 and ECW are really too slow for
>> production use anyway. Maybe that's some "sour grapes" consolation? :)
>
> Just made some tests today with a black/white ECW image covering the whole of Finland with 1 m pixel size, image size about 1200000 by 500000 pixels.  Debug log shows about 0.15 seconds rendering time at any output image size with png output to WMS. At least with this image the speed would be enough for us.  I know from earlier experience that server is slower with colour ECW imagery and jpeg or png24 output but that is not a surprise.  But we are not going to acquire extra ECW licensies and yearly fees so obviously we are going to go on with geotiffs.
>
> -Jukka Rahkonen-

I too would like some clarification about the ECW license,
specifically using ECW as a source in MapServer.

I have had excellent results with color ECWs.  I have tested
informally against RGB TIFFs, palatalized TIFFs, and ERDAS img formats
on a basic SCSI RAID and on a single IDE drive. The palatalized TIFFs
are the fastest, but look lousy. The other formats are comparable in
speed. ECWs, being smaller in size, are easier to maintain on remote
servers. The things that appear to make a significant difference in
speed are:
1. Use low compression levels. I typically use 8:1
2. Use pyramids. I know that ECW has internal support for pyramids,
but if you want to serve up fast ECW imagery, pretend that it doesn't.

Rich

-- 
Richard Greenwood
richard.greenwood at gmail.com
www.greenwoodmap.com