Watching the storms

January 18, 2010 at 12:00 PM in: weather

Want a good view of the storms hitting California and willing to work a bit for it? Download and install WeatherScope. This is a free application for looking at the huge quantities of free weather data out there. The user interface isn't great but the functionality is.

The most frequent updates on the atmosphere (about every 5 minutes) come from weather radar. WeatherScope has access to the past 24 hours of raw US radar data, while the free weather websites will show you about 45 minutes worth. 24 hours is enough to see a lot of patterns - arcs of rain sweeping in from the Pacific, blossoming into downpours when they hit a ridge.

Here's a WeatherScope saved view for base reflectivity from three overlaid radars covering north-central California (San Francisco, Sacramento, Beale AFB): sf-radars.wxscript

At least on the Mac, WeatherScope should automatically open .wxscript files. After opening the file, you should see a map of California. In the WeatherScope menu bar, go to "Window : Show Animator" and click the Play button in the Animator window. It will take a while for WeatherScope to download 24 hours worth of animation, so you won't see much to start with. Once it fills in hopefully you'll feel it was worth waiting for. Leave WeatherScope running and it will download new images as they become available.

UPDATE: Here's a much better looking sanfrancisco.wxscript courtesy of James Home.

Bad data at Bon Tempe Lake

December 29, 2009 at 12:00 PM in: maps

Got the dynamic range right on the shaded relief. (Click image for 1024x1024 version):

Alpine Lake and Bon Tempe Lake

Alpine Lake and Bon Tempe Lake (CC-by-SA license)

I've spent several days trying to figure out why the roads in the MRLC land cover data don't line up with the OpenStreetMap roads. The creeks (from NHD), elevation (from 10m NED), and roads all seem to line up in a way that matches aerial photographs. I double checked all projections, installed the latest versions of everything, lots of web research, no clue what's going on.  The roads seen in the landcover data are the right shape, they're just off in position. But they're off in position by a variable amount.

I finally noticed that the landcover doesn't even agree with itself! There are places where the landcover data indicates a road crossing open water and there is obviously no bridge. The dam on Bon Tempe lake shows that the vegetation and water are correctly aligned with OpenStreetMap, but the pink line for the road crossing the dam doesn't line up with the other landcover pixels.

Is this a known problem with MRLC?

Mt Tam Chiaroscuro

December 14, 2009 at 12:00 PM in: maps
North flank of Mt Tamalpais

North flank of Mt Tamalpais

I've been playing with making topo maps using elevation and land cover data. Enough is in place now that some of the bugs look interesting. My initial take on light and shadow turned out to be a bit aggressive.

At full size this image becomes very abstract and reminds me of camouflage. The stripes from the shaded relief look like some animal patterns, and the blockiness of the land cover data looks like MARPAT.

As a thumbnail it's more obvious what's going on:

North flank thumbnail

Another You are Here Video

October 22, 2009 at 12:00 PM in: you-are-here

On my last day at the old job I brought You are Here in for a demo. The software hasn't changed much recently but the new tablet pc sure improves it. Kirrily had a video camera handy and did this off-the-cuff demo/interview:

Redneck Windchimes

October 02, 2009 at 12:00 PM in: artifacts, photos

Assembled from bits found cleaning up a campsite this summer...

lead, brass, fishing line

materials: copper, lead, brass, fishing line

The rANch: moist, not crispy

August 31, 2009 at 12:00 PM in: photos

Another chapter in the improbable history of Cataclysmic Megashear RaNCh.

Yesterday a four-alarm fire destroyed four warehouses and damaged three others on our block in Bayview. The rAnch was unburned, in spite of fire burning on two sides. Water damage was minimal, in spite of the ladder truck overhead and firefighters tearing out the two windows in the great room in order to hose down the building in back. Here's a view through one of those windows:

Unbelievable. Our guardian angel(s) (not to mention the SF Fire Dept) were working overtime. Mauricia's painting hanging next to the window escaped with nothing more than some spray. Her studio in the next room was completely dry. The wood shop downstairs looks like it will be ok after it dries out.

We started some cleanup last night, in a surreal atmosphere of mist and smoke and floodlights as the fire trucks continued to pour water on the smoldering wreckage next door. Nobody was hurt and no residences burned.

Nothing in life is so exhilarating as to be shot at without result.
- Winston Churchill


March 30, 2009 at 12:00 PM in: photos

Sand from the base of Eureka Dunes

Desert sand has sharper edges than water-tumbled beach sand.

More exotic sand photos at

Cloud shadow

February 25, 2009 at 12:00 PM in: photos

This shadow of a cloud near the horizon stretched halfway across the sky.

This is the most pronounced cloud shadow I've ever seen. The cloud in question appears to be the bright white streak near the horizon, which is almost but not exactly lined up with the shadow. But why the strange alignment of the original cloud? It could be a contrail, but it's very thick and fluffy and seems to start very suddenly.

The shadow stretched halfway across the sky.

Scent over time

January 04, 2009 at 12:00 PM in: smell, time, music, perfume

One of the more intriguing aspects of perfumery is the evolution of scent over time. The more volatile components of a mixture ("top notes") predominate at first, and as they evaporate off they give way to the slower and heavier components of the scent ("base notes").

I'm very new to perfumes, but so far I am finding myself fascinated by the complexity of the initial scents and bored by the long and relatively simple finishes. For example, Christopher Brosius describes his Violet Empire: "the violet scent perpetually peeps out from behind a shining green veil." Indeed, out of the bottle it smells fantastic. On skin, the shining green veil soon dissipates and what remains seems floral and cloying, though a better nose than mine describes the finish as "deep woods and a mild trail of leather".

Contrast this with the development of a piece of music - many pieces start with a simple exposition of a theme, slowly building in complexity as the vocabulary gets established. This is most obvious in a Hindustani classical performance, which begins by slowly exploring the intervals of a raga within a single octave, juxtaposing only a few notes at a time and letting them fade before sounding new ones. Gradually the surrounding octaves are added to the mixture, and the soloist accelerates until many tones are ringing at once. It might take ten minutes before any rhythm is introduced, and another twenty before the fireworks really get going.

A perfume seems more like a single stroke of a gong - rich and complex when first struck, but settling down to a persistent hum. But while a gong lasts a few minutes at most, the base notes of a perfume persist for hours.

Wine tasting allows another approach - you get to take that journey from start to finish on each sip, as well as noticing the slower changes over the course of several glasses. However, wines have a much more constrained palette than what the perfumers work with.

The slowest change in scent I've ever observed took years, and was probably a chemical change rather than the gradual evaporation of volatiles. I picked a flower in Marin county - something like Artemisia Californica, but with perfect small silver-gold everlasting flowers. The sage smell lasted for months, fading to a distinct smell of maple syrup. After two years the maple scent was replaced by an increasingly powerful whiff of dried urine. It took a while to figure out where the odor was coming from, but I regretfully got rid of the flower.

Rotating Time into Space

January 04, 2009 at 12:00 PM in: dance, time

Sometimes people refer to time as a "fourth dimension", which is true in some sense but also misleading since time is qualitatively different from the three spatial dimensions. You can rotate an object so its height becomes its length or width, but in the real world you can't rotate duration into depth.

MoFrames is a collection of images that do just that. The image on the right was constructed from a video of two swing dancers, with the background removed and each video frame shifted slightly forward and overlaid using a piece of software called Recreating Movement. The MoFrames site contains more examples including a page of videos that play with time, space, and motion in unusual ways.

(via kottke)

See also Golan Levin's list of slit-scan video art and research.

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