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Guest Alex_Law

blackart doesn't work for me...

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Hi all,1. It doesn't load standard SRTM3 files. It claims that the file is not SRTM. Other programs do display and manipulate it correctly (including SRTM2BGL).2. I can use only the batch processing, but then I cannot "view" or "save" the "invisible" result. I can hack my way around this by renaming the .hgx (temporary?) file it generates - actually a standard SRTM file - and view it with another viewer...What am I doing wrong?Thanks,Alex

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Hi Alex,groping in the dark a bit here...1. Are you using the latest version, 3.75?2. Have you looked at my Blackart thread here in the forum with regards to some of the steps regarding using it?3. Can you list some of the tile names you're working with? I can download it/tem and give it a go, though I don't assume that would be the problems as I and others have used it without those issues.Cheers, Holger

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;-)Thanks for the attention, Holger.1. I am using 3.752. Yep. I've read all your posts (maybe that's the problem - too much info for the unexperienced ?)3. Here are two example tiles: N32E034.hgt and N32E035.hgt.I did a fast SRTM2BGL and saw that there is a lot of "garbage" in the sea and lakes... Tried the flatten tool but they usualy end up creating sharp rifts at the borders - not very realistic if you ask me. Anyway, I am not sure what tool to use to manually remove these bumps without creating the rifts (something like the smooth brush in PSP).In addition I am not sure how to flatten both the sea which is theoretically at 0m and lakes above or below sea level. I don't know how or if blackart can do that...But maybe I'm looking for the ultimate tool that does everything instead of looking for a toolbox. If this is the case, I couldn't find a list saying: tool A does this and tool B does that, etc... maybe that's impossible too... Am I expecting too much? Is the life of mesh "designers" that hard ;-D ?Thanks,Al

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Hi alex,you read all of my posts? Heck, I don't even do that ;-)Just tried the two tiles you mention in Blackart and they load without any problems!?! Perhaps re-install or tell us the exact steps you're using in trying to load a file (you ARE switching to "SRTM height files" when loading, I presume).What's your mesh "destination": FS or CFS? In FS you don't have to worry about non-flat water because the default LWM water files will flatten them in the sim. Not always in the correct place but that's another story (many threads about that here and in the scenery design forum). Ummm, I don't think the life of mesh designers is that hard (compared to, say, modeling an airplane in GMax) but it does take a bit of know-how and experience to provide high-quality work, just like for any other type of add-on. Matthew's great utility has the unintended consequence that the mesh design process appears to be a 1-2-3 thing but that's definitely not the case, as some recent uploaded examples show. Anyway, great to hear that you're into this and trying to use Blackart instead of the simple linear interpolators of the other utilities!Cheers, Holger

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LOL,You solved me one (big) problem. I was NOT switching to SRTM when loading... There simply was no hint that that can be done so I was using only the batch processing... Well, I tried again and really looked at the load window and discovered the "elevator" with all the formats. Now I see the light! ;-).The mesh is for FS so thanks for putting my fears to rest with the LWM hint.I guess that now it's all down to manually fill those big lakes (represented by voids) and then run Black Art again.So, is my following procedure OK?1. Load each tile and manually fix the huge water surfaces which happen to be covered by voids (maybe using PSP instead of blackart?). Save the modified files as SRTM.2. Batch process all the corrected files with the Laplacian set to 1000 and LSQR 10 for example.3. SRTM2BGL with NO interpolation.There is one thing that bothers me though, What should I do in order yo ignore the -32000 issue? I DON'T want to clip anything to 0 or to a fixed value. I want voids to be interpolated. What do't I understand?Hehehe - and you beat me with the gMax "mine is bigger than yours". Yes, I agree. Creating a plane with gMax is difficult - but then again - I am sure that there might come an aeroplane designer who will disagree .Have fun,Al

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Hi Alex,Blackart's interpolation routine will fully interpolate all voids (unlike SRTM2BGL, which often leaves patches in large voids) and thus takes care of the -32000 issue too. Since the water areas will be flattened in FS all you need to do is run the batch process once with your choice of Lapl and LSQR; in other words, forget about your first step and start with 2.Big voids are only an issue when they occur above land. In that case you should attempt to fill them with other elevation data (John describes the process with DTED0 data on his website, and there are other options as well). It didn't look like the tile you were interested in had any of those voids so you should be fine with steps 2 and 3.Good luck! Cheers,Holger

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Hi Holger,1. Yes, but what can I do when a lake is *under* the sea level. In that case the clipping "thing" simply raises it to 0m. What I've done is "paint" the lake (covered by void) it it's real altitude, and the run Black art. Is there a better - and simpler - solution to that? Please remember that I have boath sea (0m alt) and lake (negative alt) on the same tile ;-).2. What can I do about the occasion "Devil's tower-like" spikes that appear here and there. I tried to pinpoint them but it's next to imossible due to their very similar coloring to the "legal" alt points. I tried low pass filter and selective smooth but not with much success. Overdoing that would defeat the very purpose of SRTM - much better resolution.Any ideas?Best regards,Al

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Hi Alex,I took a look at one of the tiles myself and finally understand what you're getting at. Sorry, but I never dealt with below-sealevel data myself. It seems like there might be a bug in Blackart.Here are 3DEM images of the raw data (voids in blue), an interpolation with Blackart (10/1000), and a comparison interpolation with MicroDEM (search radius 200, bi-directional). It seems that Blackart attempts to interpolate all missing data to sea level if the surrounding terrain is less than 0 m, which is why even those small voids end up as spikes. Unless we both are doing something wrong here I suggest you use MicroDEM instead. Actually, the better idea is to send an email to John Childs (perhaps with my images or a link to this thread) and ask him about the issue.Cheers, Holgerhttp://forums.avsim.net/user_files/72224.jpghttp://forums.avsim.net/user_files/72225.jpghttp://forums.avsim.net/user_files/72226.jpg

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;-))Thanks for the research and pics Holger. MicroDem pics look DEFINITELY better - I had a hunch that Blackart cannot cope with both sea-level and below-seal level surfaces at the same time.I tried to use Microdem but I didn't find a way to export to SRTM or even BMP so I use it mainly as a preview tool ;-(.Meanwhile I did some manual paint job and closed the "big below sea level void", and some other small artifacts. I also cleaned the sea while at it - no big deal . Now it works perfectly. And I noticed that the many spikes that I saw (beside the Blackart-generated ones) were due to an over-zealous landclass developer that messed a bit with the mesh. I cancelled the landclass and voila! 90m SRTM mesh in all it's glory!Now I'll try to convince the landclass developer to cancel his mesh "corrections" and follow the more accurate SRTM mesh ;-D. This might turn out to be more difficult than mesh editing .Phew! This wasn't as hard as I was afraid of - you were defeinitely right! gMax beats this anyday!Best regards,Al

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Hi.I downloaded those files and had a play myself - here's my attempt. Interesting situation, with sub-sealevel lakes and normal sealevel - um - sea on the same tile.If you want the RAW file let me know and I'll email it but it looks like you've already sorted the problem.Cheers,Jim Keirhttp://forums.avsim.net/user_files/72301.jpg

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;-)Yes, I sorted out the problem though the method is not to my liking. I had to manually fill-in the "voided lake".But the problem is still n the table:How to interpolate sub-sea level voids when you also have sea on the same tile?Black-art currently does not do it, but i am sure that there are other tools which do...Anyway, my SRTM mesh is ready and extremely good, but I will release later, when I manage to convince the landclass developer to fix his mech mods... Hopefully very soon...Best,Al

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Hello Al,I am not 100% sure, but I think that my set of DEM tools could interpolate SRTM voids at sub sea level. BTW, I am revising these tools to include in my SBuilder programme.My interpolation algorthim has nothing of special - voids values are replaced by the mean of the neigbhour values. When I have a set of continuous voids, I start by replacing the void(s) which has(have) a maximum number of valid neigbhours, which is 7. When it happens the void value becomes valid value. Then I pick another one but I scan the picture from different directions. The aim is that the void region becomes "attacked" from all sides and not, simply, for example, from left to right and top to down.What triggered my post is the fact that I consider a value to be a void if it is equal to -32768 (the maximum absolute negative number that we can represent with 4 bytes signed integers). Therefore if these values are surrounded by negative values they will get interpolated as any others. But I did not check this and I do not remember the details. I will check though ...Regards, Luishttp://www.ptsim.com/downloads/DEM2BSQ.ZIP

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Thanks for the heads-up Luis,I asked myself why in the name of G.. would someone simply decide that void=0 - or any other value? The method you're using is the only one I can think of - except interpolation based on other sources - GTOPO or other topographic data.BTW, I am new to these issues - does you tool directly support hgt files load and save?Best regards,Al

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Hi,The tool converts HGT to BSQ. So the answer is yes. The BSQ is the format that MS uses but I add some positioning data on the bottom in order for my tool to handle the files better. This added information is discarded by the MS resampler. As soon as you convert the HGT to a BSQ, you can do many things with the converted to BSQ. You can filter it, interpolate, increase the sampling rate to 1 sec (in order to make possible a merge with DTED2 data), merge 2 BSQs, crop a BSQ, convert the BSQ to a bitmap, convert a bitmap to BSQ. The problem is that the tool is not very well documented.Regards, Luis

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Hmmmm - this sounds very interesting. I'll give it a try and let you know.Documentation - hehehe - developers NEVER like writing documentation... but if people ask "how I do this and that" you do not have the luxury of saying "RTFM" .But you need some documentation in order to make your tool accessible. More accessible - more users. More users, more feedback. More feedback - more headacke . Forget I said it!Best regards,Al

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