Walking on Lava
It is kind of time for another round of pictures from Hawaii. Since everyone prefer lava and since Hawaii in the only place in the world where tourists freely roam on an active volcano, only a few centimeters from glowing lava, I shall start with the pictures of my hikes on the Kilauea.
But first, since this is a geek's blog, I will do some technical rambling. Digital camera manufactures boast that their products can capture a large amount of megapixels. Is this any good for the user? I say hell no! I'll be talking trough my hat since I only used one digital camera seriously but I received enough pictures from others that I'm confident that what I say is true.
Do you recall those new parents who sent you an email with only a few pictures totaling several megabytes? Why do they do that? Don't they know that you are using a monitor that can't display such a large image? Do they expect you to zoom in on this youngling to convince yourself that its eyes are closed? Do they expect you to print this picture? A cheap printer with cheap paper can't match this resolution and sorry buddies, I won't take your pix to a print shop. I'm not saying that parent should not send emails with pictures, what I'm saying is: please, no pictures larger that 300k!
Have you ever tried to zoom on the youngling to convince yourself that its eyes are closed? I'm pretty sure that no parents have because they would instantly stop sending those large files. The crappy digital camera that we have save pictures in jpeg with compression aggressively cranked-up. You might recall that jpeg is a lossy compression format. That means that when you crank it up, you loose something in your picture and it gets replace by an ugly artefact that is easier to compress. On all the cameras that I saw, it wasn't possible to save in png or to tune the jpeg compression so your only hope to get a clear picture is to zoom out. Here is an example of a perfect image, the same image with conservative jpeg compression, with "standard" compression and with aggressive compression.
You could perform the same experiment on your own images with something like this:
for c in 90 70 50;
do convert -quality $c shoe-wrack.png shoe-wrack-$c.jpg;done
As you can see, jpeg compression destroys precisely what makes an image great: the fine details and the smooth gradients. The images produced by your digital camera are useless at the resolution they are saved at but you can still salvage them for publication now that you know how jpeg works. The idea is to zoom out and to average the resulting pixels with many pixels from the large images. I don't intend to have you code anything yet since I'm only saying that you should please rescale your images before you reach your favorite email client. I expected an easy path to batch rescaling a bunch of pictures and there is one but the command is quite obscure:
rename 'y/A-Z/a-z/;s/hpim//' *.JPG
find -name "*.jpg" -exec convert -affine "0.5,0,0,0.5,0,0" \
-transform -quality 85 {} {} \;
I promise that if you run this command on anything produced by your crappy digital camera no one will mind that you send him several pictures of your new born.
So, how about lava you ask? Yeah, I wanted to publish the whole thing but I was stuck with several hundred megabytes of jpeg compression mess. Once I made my mind that there wasn't anything that I could do with the hi-res images, everything was so simple: I could just pack all the images in a tarball and let you enjoy the lava-pack-1. Note that there is no lava-pack-2 but who knows, I might return to Hawaii one of these days. Also noteworthy is the fact that the latest version of tar auto detects the compression algorithm. That means that if you are running a non-baroque version of GNU/Linux you can just type
tar -xvf lava-pack-1.tar.bz2
instead of
tar -zxvf lava-pack-1.tar.bz2 # argh, error!
tar -jxvf lava-pack-1.tar.bz2 # finally!
In this picture pack you will find several pictures taken around the Kilauea during August 2006. The pictures up to 0327 were taken during the field trip organized by the CASS. I I liked the Big Island so much that I went back for a few days after the CASS. The rest of the pictures are from this second trip. The weather is great in Hawaii and there are no nasties: serpents, mosquitos, jehova witnesses, ... So I went camping with nothing more than my hammock, a rain poncho that doubled as a tarp and my zen stove. Mine is a Cobra, completely pressfit without glue or top screw but with inner packing because my previous stove shoved how bad a spilling can get.
I used a travel hammock from hammocks.com . This hammock isn't as comfortable as a Mayan but it's still better than self inflatable matresses and probably better than most beds. It will pack really tight in a small sack and makes a pretty good travel companion. The hammock is pretty much waterproof so when it rains, it will collect water an funnel it up to your butt. The poncho wasn't large enough to cover the whole thing so next time I'll bring a larger tarp. The Kilauea is 1250 meters above sea level. It can get chill at night but a cheap sleeping bag is definitely enough. The main concern should be drinkable water: in Hawaii the sun shines hard and when you walk on a pitch black lava field you get thirsty fast. The Volcano Park has several drinking fountain so you rarely need to carry more than 2 litters.
When paying for entrance in the Volcano Park you can camp in a nearby campground or go for the real thing and register for back country camping. I tried both and back country is definitely worth it but it's not for the faint of heart. You have to hike for at least an hour on the lava field with no indication except an occasional pile of rock. Once there you have a perfect starry nigh with glowing red lava all over the horizon line.
The lava field is surrounded by a giant fern forest so you can't hang a hammock unless you reach the right spot. Don't even think about pitching a tent on the lava field, this stuff is sharp even though it doesn't look that way and anyone who touches it end up with a bleeding hand.
The Volcano Park is great for interpretation. You can see sulfur banks, lava tubes and lots of helpful signs but if you want to get close to the flowing stuff and if you want to see lava cascades, you need to reach the Kilauea from the Pahoa side. I was a bit adventurous and I got caught between lava fingers. As long as you have the wind on your back, you can walk about 30 cm from the active flow. When the wind blows the other way around (or even just stop blowing), heat is unbearable and sulfuric gasses are suffocating. When I got trapped could have walked back but I was low on water and after a few hours looking at lava you really feel that you understand it (OK sulfur might have something to do with it).
The old lava is pitch black. The recent one is kind of dark silvery. As long as you are on the black stuff you are safe (well, you are still on an active volcano). It gets tricky if you want to cross the silvery stuff. Really fresh lava has a porous glassy appearance and as it cools down, it cracks and small chips fly away. So I made my way jumping from a cracked silvery patch to the other. At the end I could feel intense heat from the sole of my army boots but I was back on a black patch with the wind on my back. I guess that running shoes would have melted, we don't pay enough attention to the melting point of the sole when we buy footwear.
In case you are wondering, when the lava falls into the ocean it instantly explodes into tiny fragments that gets washed away for a few miles where it forms black sand beaches.
Thats it for the lava stories (unless you pay me a beer for a live summary), stay tuned for more tales of Hawaii!