Thanks Mark. Mind if I ask a few more questions?
1) Have you found jpeg encoded tif to be a fast vs mrsid/ecw? Does it even
matter once you put the Mapcache in front?
2) How much drive space does your cache take compared to your imagery?
Thanks again,
-Andy
PS: sorry if this double posts.
On 05/28/2015 07:37 AM, Mark Volz wrote:
Hello,
Andy Colson asked me about my interactive mapping setup and how I was able to
get the air photos to run fast. I figure there may be a couple other people
that might want to know what I did to improve the speed of my service at:
http://geomoose.lyonco.org/geomoose2/geomoose.html#. Please note that this
list is not exhaustive, nor am I an expert. So some people may want to add or
refute some of this information.
*Use the same projection for everything. Don't make MapServer have to deal
with projecting imagery or data to a different coordinate system.
*Use a map cache. Mapcache is integrated with some distributions of MapServer,
but there are several out there each with their own advantages and
disadvantages.
*Disable fractional zoom on your application. In addition make sure your
application is set up to use the same scales, tile size, and tile origin (grid)
as your map cache. If any of these don't match then your mapcache will need to
perform extra work for each request.
*Search for "WMS Performance Shootout." They are starting to get old now, but
they contain many tidbits on how to improve speed.
*You may want to look at http://www.mapserver.org/optimization/raster.html.
This page mentions what format you should use, and how to create internal tiles.
*Use PROCESSING "OVERSAMPLE_RATIO=1". If I recall correctly MapServer uses an
oversample ratio of 2.5 so it is sampling the raster at 180dpi to create a 72 dpi image.
This is good for scientific applications, but it may be unnecessary for air photos. Just
be warned that low oversample ratios can create grainer images.
I think that by using a cache, making sure your application grid matches your cache, and
configuring oversample_ratio=1 so MapServer doesn't need to do extra work will be more
important than the actual server specs. What you need for a server really depends on
more factors. Our server is "decent" now but we use to have an old GIS server
that performed well with the above tips.
Sincerely,
Mark Volz, GISP
Lyon County GIS Coordinator
-----Original Message-----
From: Andy Colson [mailto:[email protected]]
Sent: Wednesday, May 27, 2015 8:50 AM
To: Mark Volz; Rahkonen Jukka (MML)
Cc: [email protected]
Subject: Re: [mapserver-users] stretching imagery in MapServer
Hi Mark. Two questions for you:
1) I know it might be a bunch of extra work, but I don't suppose you could post
some before and after shots (or urls or whatever). I really have no idea what
sort of change your talking about.
2) Holy freaking cow you have fast imagery. I don't suppose you could share
some processing/hardware/setup secrets?
Thanks
-Andy
On 5/26/2015 2:07 PM, Mark Volz wrote:
Jukka, (and others)
Thank you for your reply. I think I figured out how lut works. If
you don't mind please check and make sure I have this correct:
I can use ArcGIS to report the correct input and output values for a
n=2.5 standard deviation by going to
layers->symbology->stretch->histograms->Info window. Once I have
layers->symbology->stretch->histograms->those
values I can modify my map file to include for example:
PROCESSING "LUT_1=73:0,226:255" #changes red band input of 0-73 to 0,
inputs of 226-255 to 255, inputs between 73-226 linearly interpolated.
PROCESSING "LUT_2=60:0,199:255" #changes green band input of 0-60 to
0, inputs of 199-255 to 255, inputs between 60-199 linearly interpolated.
PROCESSING "LUT_3=35:0,155:255" #changes blue band input of 0-35 to 0,
inputs of 155-255 to 255, inputs between 35-155 linearly interpolated.
P.S.
Before I knew what the heck I was doing with LUT I noticed that I
could identify wet areas, and tree cover quite easily with the
following
combinations:
PROCESSING "LUT=50:50,60:250,70:250" is a good way to identify tree
cover.
PROCESSING "LUT=50:50,60:250,70:70" is a good way to identify wet areas.
Thank You
Sincerely,
*Mark Volz, GISP*
*From:*Rahkonen Jukka (MML)
[mailto:[email protected]]
*Sent:* Monday, May 25, 2015 9:18 AM
*To:* Mark Volz; [email protected]
*Subject:* Re: stretching imagery in MapServer
Hi,
As far as I know automatic stretch by standard deviation is not
supported. You can do automatic min-max stretch with PROCESSING
"SCALE=AUTO". If your source data is uniform you may reach a good
result with manual scale settings or with PROCESSING "LUT= "
-Jukka Rahkonen-
Mark Volz wrote:
Hello,
I added our new Pictometry Air Photos on our mapping site at
http://geomoose.lyonco.org/geomoose2/geomoose.html. The air photos
seem somewhat washed out. In ArcGIS I was able to get a nicer looking
image by stretching the air photo using standard deviations. Can we
stretch imagery in MapServer? If not please let me know if you have a
comment regarding how I can improve the image quality.
Thanks
Sincerely,
*Mark Volz, GISP*
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