On Sat, 29 Nov 2003 22:09:24 GMT
Kyler Laird wrote:

[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.


How do you and others mean to use these charts? Laptop in the plane?
Just for reference during flight planning? Print them and take them along?



R. Hubbell


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