AVIATIONTOOLBOX: How do you like your maps stitched?

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

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, *
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* (Just my 20 USm$) *
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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

writes:

: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.

What makes you think that? (I'd like for you to be correct, but I've been
assuming they don't have it like that.)

--kyler

"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