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Holger

reducing blockiness of satellite imagery?

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Hi all:I'm working with Landsat 7 ETM 15-m data in the Rocky Mountains of B.C. and I'm looking for ideas to minimize the 'blockiness' of the source data. The pictures below show the obvious pixels after running resample.exe (v1) with the raw 15-m data (please disregard the missing or off-tone colors; right now I'm just concerned with resolution and image placement). Most blocks are 4x4 pixels, i.e. ~20m. It appears that resample.exe uses a nearest-neighbour approach to resampling (to 4.8m) rather than a bilinear or bicubic transform. I have experimented with changing pixel size in Photoshop (7.5m or 3.75m, with bicubic transform) prior to using resample.exe and it helps to reduce blockiness but also increases file size a lot and doesn't help too much with the overall blurry appearance at lower altitudes. I realize that there's no way to add detail that isn't in the source data but I was wondering whether anyone has come up with a satisfactory procedure (resizing, sharpening, filters, etc.) for making these kinds of images appear less blocky in FS?Cheers, Holger http://forums.avsim.net/user_files/37077.jpghttp://forums.avsim.net/user_files/37078.jpghttp://forums.avsim.net/user_files/37079.jpg

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Hello Holger,As you say, the problem lies with your source. No way to get good output from low resolution images. I am even surprised that it looks so good, but you can probably get by using this source in mountainous areas.Elrond once (long ago) provided us with a handy little tool for resizing images with better filters, including a top-of-the-line Lanczos3 filter. But, I don't know if it is available on his web site, or even if his web site if is still up, nor do I know the URL!The best solution, of course, is a better source image. Toporama provides high-resolution aerial images for all of Canada. The last time I was there (months ago), they were down and redoing the web site. Maybe they are back up by now. But, if not, the person in charge was kind enough to provide Joe Sumrall a link and password; he transmitted it to me and I pass it on to you, in case you are interested.The Toporama Web site is temporarily unavailable.We expect to have an improved and updated version back on-line by the end of the year. Meanwhile you can access the old site at the address below, using "topoin" as a password. http://toporama.cits.rncan.gc.ca/topoaccess.html Best regards, Odette Trottier

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Hi All,>Hello Holger,>>As you say, the problem lies with your source. No way to get>good output from low resolution images. I am even surprised>that it looks so good, but you can probably get by using this>source in mountainous areas.>>Elrond once (long ago) provided us with a handy little tool>for resizing images with better filters, including a>top-of-the-line Lanczos3 filter. But, I don't know if it is>available on his web site, or even if his web site if is still>up, nor do I know the URL!Agree,I also use Elronds excellent FS-Resample Tools with great results (do not let MSFS-resample.exe resize your image), but regardless of if you have nice 1ft/pix or 30m/pix imagery I have found over much use that using sharpen & unsharpen masking before and after resizing the image to work the best for the final results (careful not too much), also you should setup your video card drivers to render the scene at its sharpest in FS so that you can see the image the same as those who also use those settings i.e.: 8x-Aniso w/trilenear filtering etc.Here is one of my Rochester Photoreal fall textures resampled from 1ft/pix to 4.75m (too bad we cant use higher res) this is as clear as I can get it without having too many artifacts (uncompressed):Cobbs Hill reservoir fall texture:http://www.frontiernet.net/~pleatzaw/image...121212002fa.bmpAirport summer texture:http://www.frontiernet.net/~pleatzaw/image...121203032Su.bmpYou also want to have some examples of local landclass textures opened so that you can adjust color balance and tone so that your image will do its best to "blend in" with the surroundings for a given season, though this isn't always possible nor always even desired in certain situations bla bla bla...I'll just shut up now...:)

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Hi Luis and Paul:Luis, thanks for the tips and the link to the Toporama website (including the password!). The scanned topo maps on that site are really nice and useful but the orthophotos are of very poor quality; someone did a bad job in transforming the source images to .gif format - see this example of Lake Louise:http://forums.avsim.net/user_files/37248.jpgFortunately, there is an alternative source (for most of British Columbia) for high-res orthoimages in grayscale similar to the US Terraserver. Here's the URL http://www.em.gov.bc.ca/mining/Geolsurv/MapPlace/default.htm (use the 'British Columbia Base Map' link at the bottom) and an example: http://forums.avsim.net/user_files/37252.jpgHowever, at the moment I'm interested in covering larger 'backwoods' areas and believe (hope?) that the 15-m Landsat data are a suitable source.I have completed a few more tests with resample.exe, changing pixel size and using sharpening filters in Photoshop *prior* to resampling. Here are two samples of the results: http://forums.avsim.net/user_files/37253.jpghttp://forums.avsim.net/user_files/37254.jpgThe b&w image has pixel sizes of 15m, 7.5m, and 3.75m, respectively. In other words, the leftmost panel is the resolution I used for the grayscale scenes in the original post above. So there's definitely an advantage to matching the 4.8m FS resolution as closely as possible prior to resampling, just like anyone here has stated ;-)Paul, those are two nice and crisp custom textures!!! Obviously, way out of reach with my source data, though I could use the high-res orthoimages in developed areas to merge with or replace the satellite data. Good point about overdoing the sharpening; the lower right panel of my color image tests is probably an example for too much sharpening.So, is there an URL for Elrond's tool? I'm probably fine with Photoshop but wouldn't mind checking it out.Thanks again for your input. I'll keep on tweaking...Cheers, Holger

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Hello Holger,This looks great. You seem to have found a reasonably acceptable solution.Thanks for the links - very useful and a lot better than Toporama.I have Elrond's utility and do not put it up here because it is over 330 KB. If you wish, I can send it to you. Just give me an address.Best regards.Luis

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lets see if I can attach Elrond's utility, your email is bouncing back undelivered...nope....too big to attach.oh well, out of ideas at the moment.Bob Bernstein

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Hi Bob and Luis,If it would indeed be useful for anyone, either of you feel free to zip the util and upload it to the AVSIM library if you desire (include my standard licence and copyright boilerplate notice -as shown below- in a readme if I didn't send one to you - replace the contents in the < > brackets with the util name and year of course).I don't have the util or the source anymore, so I'd rather not redo a new one from scratch (and round one out feature wise) unless there is a demonstrated need. The download count of the zip you might upload would let me know pretty well.--Copyright, License and Disclaimer------------------------------------ is Copyright © by Elrond Elvish. All rights reserved. is released as Freeware under the following license:Redistribution and use in binary form is permitted provided that the following conditions are met:1. Redistributions is only allowed in binary form and must keep intact the full and unmodified original zip archive. This copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials must not be removed or modified from this original form.2. This software must only be distributed without charge or attached license, except in the case of a nominal distribution fee of no more than $1, if required. You may not charge for this software in and of itself.3. You may not reverse engineer or decompile the provided executable without prior written consent.THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.--Take care,Elrond

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Hi Elrond,I still have the original colector edition Zip file with your Copyright, License and Disclaimer still intact. If you would like I would be more than happy to upload it here to the Avsim file library later tonight. How are you?Hope all is fine.

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Hey Paul,There are two different (and unreleased) tools being discussed here. The one I think you're referring to is ResampleTools Beta 0.95. The one Luis and Bob are referring to is a utility that resizes images using a variety of user selectable filters to the correct size based on known m/p of the source image - it is a single shot/use test utility that I created for my filters code. I can't even remember what I named the second one :-lol.Regardless of which utility being referred to, any of you feel free to upload them AVSIM as you see fit. I probably should have done that when I created them, but forgot to. Neither utility was ever completed to a "release" state in my mind, but if they can be useful to anyone in their existing forms I have no problem with their upload - so thanks for the offer.As for me, I'm doing pretty well, thanks! I still have to battle with continuing health problems, but it gets easier to do so as it becomes the "norm" :-lol. Otherwise, all is well on the homefront and I'm enjoying the unfortunately slipping summer.Its good to see you still around and active in the community here - specially on the design side. I hope all is well with you and yours as well.Take care,Elrond

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Hi all:Luis and Bob, thanks for offering to send me Elrond's utility. Looks like it'll be available soon at the webservers and I'm looking forward to giving it a try.Meanwhile, I have compiled my first full-color satellite image, with changes to the pixel resolution and some sharpening prior to using resample. The results look pretty encouraging for 15-m data, don't you think?Now I have to add the watermask and nightlight and (perhaps) autogen via VTP2 placement.Thanks again for all the help. Cheers, Holger http://forums.avsim.net/user_files/37492.jpghttp://forums.avsim.net/user_files/37493.jpg

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Stunning results, Holger. Looks really good.I had remarked a month or two ago in the TerraBuilder forum that it might be preferable to use source images with resolution lower than 4.8 meters per pixel. Microsoft seems to have used half that resolution for their photoreal areas and this gives good results and reduces blockiness considerably. So you are not far off with your source.Good to see Elrond around here from time to time. Thanks for stopping by and hopefully you will continue to do so.I also use FS Resample Tools and find it extremely simple to use and quite elegant in the interface. The image tool, by the way, was named ... "Image Tool" by Elrond - talk about descriptive names!Bob, I shall let you put both tools in the AvSim library, since you offered to do it first. Please let me know if there is any problem so that I can do it.Best regards.Luis

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>Stunning results, Holger. Looks really good.Dito that Holger, very impresive!Luis,>Microsoft seems to>have used half that resolution for their photoreal areas and>this gives good results and reduces blockiness considerably.>So you are not far off with your source.What makes you feel this way? I find the Bicubic looking resampling they seem to use very anoying though at 4.75m there is not much you can do, I prefer Antialiased with a little exagerated or over-sharpening, I have redone sections of the default photoreal Chicago (re-inserted the river) with much better results than what MS did at the same res but this after many years of trial and error and error etc. :)

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Hello Paul,Concerning the use of lower resolution images, I noticed that Microsoft uses 8 meter per pixel images for the Niagara Falls example. Also, flying over New York, I could not make out most of the detail, because ... there is NO detail. Look for anything, the West Side Drive, Union Square, you will not see them, because they seem to have used lower resolution images. Same thing with the Chicago scenery - no quadrangle or mall at the U. of C., for example.I saw the images of your Chicago re-make, and that was much better as far as detail is concerned.But, my point (or, rather, just an idea that I threw out for consideration and possible discussion) is that great detail implies a blocky appearance at low altitudes, for example, 1000 AGL. Of couse, at normal cruise altitude, high resolution scenery looks great, and your Rochester is incredible. If the entire world looked like that, we might gripe a little less about the unstable flight models (or maybe not!)But, less detail, that is, lower resolution sources, means that there is less to appear blocky when scud-running, since most of the texture is solid colors.Perhaps, what I am trying to convey is that there should be some way to avoid blockiness of textures when flying close to them, and using lower resolution images might be a solution (or not, depending on whether we are in favor of high detail or less blockiness.)Just an idea to throw out and see if anyone has comments.Best regards.Luis

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Hi,I've read all your messages and they give me help !However, I've got some questions to ask you :- With ImageTools, Luis said that the "Lanczos3" filter was the best filter. I made some tests and I find that the "Bicubic" filter gives the best results with my satellite pictures. Am I wrong ?- Holger, where are the "sharpening filters" in Photoshop ? Which option do you use and how did you do to have such wonderful pictures ?As for me, I also have blockiness in some photosatellite pictures.Regards,;-)Damien BRUNET.e-mail : damien.brunet@udb.fr.st

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Hi Damien:I briefly looked at Elrond's utility and compared "bicubic" in Photoshop with his "Lanczos3" filter. For my source resolution (15 meters) the results are nearly identical. The Lanczos3 has slightly less jagged edges, which is probably more noticable at higher source resolutions. You have the right idea: do tests with your specific image and pick the one that provides better results for you.Photoshop sharpening tools are (surprise, surprise) in the menu Filter > Sharpen. The 'Unsharpen Mask' is the one to use as it provides a number of options. Search the help file for 'unsharpen' and it tells you what the parameters do. I found Amount:150%, Radius: 1.5 pixels, and Threshold: 5 levels best for my source image. I run the unsharpen mask on the original image *before* increasing the resolution (via 'Image Size') and also follow the tip on the Photoshop help page to convert the RGB image into Image > Mode > Lab Color and run unsharp mask on the Lightness band only (selected via Windows > Show Channels, then click on the Lightness channel). However, the optimum procedure for your type of image will probably differ and there's no way around experimenting and reading the documentation.Cheers, Holger

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