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#21
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Hi Kyler,
I have all of the U.S. sectionals broken up into chunks similar to what you are describing for my flight planner, AirPlan. My software then assembles the tiles when rendering the planning map to show the sectionals seamlessly behind the main map. I don't give the charts away, but at $2.00 per chart I am pretty much just covering my subscription costs and covering the cost of manipulating the images to create the tiles. Dean Wilkinson http://www.razorsedgesoft.com/airplan Kyler Laird wrote in message ... [As I mentioned earlier, I'm going to use this "AVIATIONTOOLBOX" keyword so that those who'd like to keep up with these projects can do so easily without the annoyance of using a mailing list and others can easily skip/ killfile them. If you have better suggestions, please feel free to send them to me directly or hash it out here. I don't plan to always post to comp.infosystems.gis but I thought this topic would be good to address there.] Recently I've been working a lot on manipulating the FAA sectionals I purchased. http://aviationtoolbox.org/raw_data/FAA_sectionals/ I've been amazed by the hundreds of people who have downloaded this data. There's apparently some interest in it so I'd like to solicit input on some of the projects I'm pursuing with the data. Right now I'm working on breaking up the maps into easily-used subimages. I do this (using GDAL) by hacking off all of the stuff around the maps, converting them to RGB, warping them to match the Wichita sectional, and then cutting them into chunks. The tricky part is that the maps overlap. For the North and South sides, this usually isn't a problem. Different regions however can depict the same geographic area quite differently. Choosing how to display these areas of overlap isn't obvious to me. I've made a couple of example attempts. The first http://aviationtoolbox.org/tmp/chunk_furthest.jpg simply chooses whatever pixel was furthest from the nearest edge in the original map. That does a fairly good job, but there is some information that is just lost - it's near the edge on both maps, so it isn't shown at all. (See the "PINONCANYON0 MSL" area on Denver/Wichita border.) The next http://aviationtoolbox.org/tmp/chunk-blended.jpg is a bit more complicated. The weighting of the pixels fades toward the edges so that the maps blend into each other. Sometimes this looks much better to me, but sometimes it looks like I'm trying to read in turbulence. (See the Dalhart airport/VOR.) The big advantage is that no information is lost. Another possibility I'm going to pursue is prioritizing the colors so that some colors (blue, maroon, black, ...) take complete priority over more "backgroundish" colors. That could make for some strange looking airports (See Miller dear Dalhart.) but I think it might look "cleaner" without information loss. So...anyone have strong feelings about how this should be done? Thank you. --kyler |
#22
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Kyler Laird wrote:
:Good work! Not sure how to do the "fading" any better than what you've got. Of course, the *real* way to :do this would be to try to get ahold of the vector-based info from the FAA directly. That'd be sweet. : I'm sure they'd like to have it too. So they've only got the bitmaps too? Seems odd... SOMEBODY must have the vector art. -Cory -- ************************************************** *********************** * The prime directive of Linux: * * - learn what you don't know, * * - teach what you do. * * (Just my 20 USm$) * ************************************************** *********************** |
#23
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Good work! Not sure how to do the "fading" any better than what you've got. Of course, the *real* way to do this would be to try to get ahold of the vector-based info from the FAA directly. That'd be sweet. I'm sure they'd like to have it too. --kyler Would you happen to know just what terrain data set they use? matthew f g |
#24
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#25
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"Matthew F. G." writes:
Would you happen to know just what terrain data set they use? No, but I do see on the front of each sectional there's a note (right under the map) that says "Topographic data corrected to XXXXX". BTW, the FAA is offering a new set of high-resolution digital elevation data for right around some airports. It's expensive and doesn't seem to add a lot of value (for my purposes) for what's out there already so I'm not planning to get it. --kyler |
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