[Geomoose-users] Estimating tile size

Tue Mar 5 05:58:55 PST 2013

Hello,

I think this has more to do with Openlayers, which GeoMOOSE uses to display maps on the client side.  GeoMOOSE uses Openlayers 2.x, which to my knowledge, does not load load tiles in this way.  I think the next version of Openlayers, which is in development will subsample existing tiles so that there is never any white space on the map.  I don't remember what the presentation is called, however I think it is on youtube.  In the meantime I have been quite satisfied with mapcache, which is included with some Mapserver installations. It takes about 16ms to 100ms to serve tiles.

Mark Volz
GIS Specialist

From: geomoose-users-bounces at lists.osgeo.org [mailto:geomoose-users-bounces at lists.osgeo.org] On Behalf Of Matej Mailing
Sent: Tuesday, March 05, 2013 7:41 AM
To: Paul Wickman
Cc: geomoose-users at lists.osgeo.org
Subject: Re: [Geomoose-users] Estimating tile size

Hi,

this is almost like spamming, but it is related to the issue: Google Maps for example shows very rough rasters when zooming and then loads more details when you stop zooming or moving. We also have a number of installations where such raster's display (first rough and then detailed) would be very useful. Can this be done with GM and perhaps more Mapserver?

Thanks,
Matej

2013/1/30 Paul Wickman <paul at flatrockgeo.com<mailto:paul at flatrockgeo.com>>
Thanks for the spreadsheet, Jim.  That helps a lot.

On Wed, Jan 30, 2013 at 10:07 AM, James Klassen <klassen.js at gmail.com<mailto:klassen.js at gmail.com>> wrote:
I'd guess is in JPEGs you are looking at ~23GB and about 346GB uncompressed for all levels.  The top level (most pixels) will be ~2/3 the size of all of the levels combined.  I've attached a spreadsheet (ODS) that I've worked up to estimate tile sizes.  (My guess is it will get blocked by the list, so if anyone is interested email me.)

Which tool you use kind of depends on how you plan on serving it.  Direct from MapServer has a different optimization strategy than if you are using MapCache or MapProxy.  I'm not sure how portable the tools I worked on are.  The one I did at the city was all in C and was essentially a modified shp2img with the tile calculation added and some extra stuff removed.  What I am using now is ruby based and relies on PostGIS for indexes and MapServer for rendering.  The net result is the same though.

The big thing quality wise it to be sure to use -r average (GDAL) or PROCESSING "RESAMPLE=AVERAGE" (mapserver) so the zoomed out levels aren't all speckled as happens when using the default nearest neighbor sampling.

On Tue, Jan 29, 2013 at 1:25 PM, Basques, Bob (CI-StPaul) <bob.basques at ci.stpaul.mn.us<mailto:bob.basques at ci.stpaul.mn.us>> wrote:
Paul,

The fastest approach has and seems to still be using MapServer to generate the tiles, via a script.  Jim K. has even verified this within the last couple of weeks, since he tried improving on the original system we used here and came back to it in the end with some minor upgrades.

It doesn't really matter how you get there, even if it takes a little longer.  I think there are some MapServer utilities that we used originally on this layer.  You may want to experiment for yourself on what works best for what.

Also, in our experience, we've had best results using Jpeg (NOT JPEG2000!!) for aerials and PNGs for overlay tiles.

Bobb

From: Paul Wickman [mailto:paul at flatrockgeo.com<mailto:paul at flatrockgeo.com>]
Sent: Tuesday, January 29, 2013 1:18 PM
To: Basques, Bob (CI-StPaul)
Cc: Brent Fraser; geomoose-users at lists.osgeo.org<mailto:geomoose-users at lists.osgeo.org>

Subject: Re: [Geomoose-users] Estimating tile size

Thank you kindly, Bob.  Did you use gdal2tiles.py or is there another utility you like better?

On Tue, Jan 29, 2013 at 1:08 PM, Basques, Bob (CI-StPaul) <bob.basques at ci.stpaul.mn.us<mailto:bob.basques at ci.stpaul.mn.us>> wrote:
Paul,

For reference, I'm looking at a layer here for the City, about 56sq mi coverage at 6in pxels.  Using Jpeg tiles, 1000x1000pxels (500x500 ground units).

Keep in mind that the City is not a rectangle . . . but the levels break down like so:

(L0) ~27,000 tiles = 1.5 GB
(L1) ~ 4500 tiles = 420MB
(L2) ~ 1140 Tiles = 123MB
(L3) ~ 293 tiles = 35MB
(L4) ~ 83 tiles = 9.4MB
(L5) ~ 28 tiles = 2.5MB

These were generated from MRSID files originally, so I can't give you a number on disksize, since MRSIDs are basically compiled Pyramids to begin with.  I have some other layers that started as flat rasters such as your TIFFs if you want me to put something together for those, let me know.

Bobb

From: geomoose-users-bounces at lists.osgeo.org<mailto:geomoose-users-bounces at lists.osgeo.org> [mailto:geomoose-users-bounces at lists.osgeo.org<mailto:geomoose-users-bounces at lists.osgeo.org>] On Behalf Of Paul Wickman
Sent: Tuesday, January 29, 2013 11:28 AM
To: Brent Fraser
Cc: geomoose-users at lists.osgeo.org<mailto:geomoose-users at lists.osgeo.org>
Subject: Re: [Geomoose-users] Estimating tile size

Yes, bytes.  Zowie...   I have a TIFF of an air photo for one of our other municipalities (also 6-inch resolution), which is 20 GB (uncompress).  That coverage is only ~40 square miles.  So, for a single ~800 square mile county also at 6-inch resolution I'd potentially be looking at 400 GB for the uncompressed source or...  somewhere on the order of ~800 GB tiled?  Does that sound right?

Anybody from MnGeo on this list with any input?

On Tue, Jan 29, 2013 at 11:15 AM, Brent Fraser <bfraser at geoanalytic.com<mailto:bfraser at geoanalytic.com>> wrote:
Do you mean how many bytes?

Looking at my Landsat tile pyramids (levels 4 to 12), they're about the same number of bytes (hmm, I expected them to be double...)

But my source images:
    - no compression on existing files (tiffs, e.g not jpeg)
    - 3 band (color) imagery

The resulting tiles:
    - compressed PNGs
    - four bands (one alpha channel for transparency)

So  my guess is somewhere between "same size" to "double the number of bytes" (unless the source imagery is compressed, then it will be 5 to 10 times larger)

Best Regards,

Brent Fraser
On 1/28/2013 5:53 PM, Paul Wickman wrote:
Greetings,

I know this type of question goes around often in various flavors.  Difficult to estimate exact size of rendered tiles, but thought I'd try to get some opinions.

I see this questions asked in a variety of ways and I know it's not exactly precise on how to get the answer, but I'll throw my question out to see what I get ;)

We have a client who would like us to tile and serve up high-resolution aerial photography that they own. The area is about 800 square miles and the imagery is 6-inch resolution. They'd like to be able to view the imagery at zoom levels 11 through 20 (with level 20 being 1 pixel=6 inches). Is there any way at all to determine how large a resulting raster tile set might be?

Many thanks,
  Paul

--
Paul Wickman
CTO | Flat Rock Geographics
612.280.5850<tel:612.280.5850> | paul at flatrockgeo.com<mailto:paul at flatrockgeo.com>
www.flatrockgeo.com<http://www.flatrockgeo.com> | twitter.com/flatrockgeo<http://twitter.com/flatrockgeo>

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Paul Wickman
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www.flatrockgeo.com<http://www.flatrockgeo.com> | twitter.com/flatrockgeo<http://twitter.com/flatrockgeo>

--
Paul Wickman
CTO | Flat Rock Geographics
612.280.5850<tel:612.280.5850> | paul at flatrockgeo.com<mailto:paul at flatrockgeo.com>
www.flatrockgeo.com<http://www.flatrockgeo.com> | twitter.com/flatrockgeo<http://twitter.com/flatrockgeo>

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Paul Wickman
CTO | Flat Rock Geographics
612.280.5850<tel:612.280.5850> | paul at flatrockgeo.com<mailto:paul at flatrockgeo.com>
www.flatrockgeo.com<http://www.flatrockgeo.com> | twitter.com/flatrockgeo<http://twitter.com/flatrockgeo>

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