I need to get back into the swing of things, which will take me a while. First I had to go to the airport, to return the Cinquecento, and walk back the 4 kilometers back to town through farmland country. I stopped at the open-air market to buy carrots and wild mushrooms, and when I got back home I started a slow-cook stew with a carcasse de canard (the bones of a duck) that I bought for one euro at the supermarket (wonderful things you can find at the supermarket here). While that cooked I caught up on my blog and started on a new chapter of my book, and now I have to contemplate what my next few days will look like.
The loss of my
favorite travel companions, The Ashby Trio, has indeed had an effect in my
mood, so instead of going out to look for adventure, I spent the day “moping”
in front of my computer. As it turns out, it was quite an adventure in its own
right! I immersed myself into the intricacies of OpenTopography.org, which is a website that
hosts topographic data obtained mostly by LIDAR (LIght Detection And
Ranging), a technique in which a beam of laser light is beamed from an
airplane toward the ground, and the time of the reflection return is measured
super-accurately (thank you precise electronics), so that knowing the
propagation speed of light (300,000 km/sec) and the two way time, they can
calculate distance to centimeter level. Knowing the altitude of the plane with
great accuracy, you can then figure out the elevation of the ground. Like an
old-fashioned topographic survey, but with several values within a square
meter, so the precision of the survey is fantastic. “Big deal”, says you, but
with that high degree of accuracy many things are possible that would not be
feasible using the old methods.
OpenTopography.org (OT)
is a project financed by the National Science Foundation, which aims at
bringing this type of high-quality topographic data to a lowly user, like moi.
I first made use of the service three years ago, during the pandemic, to bring
high resolution 3-D images to my Field Geology students, but recently I started
a hydrology project at the intersection of the San Joaquin and Tuolumne Rivers,
and I wanted by student co-workers to work with a high-quality topographic
database. So we have downloaded data from OT and now have to learn how to use
it. Fortunately for us, the OT folks have prepared a wonderful set of
educational videos, and I spent a happy day looking through them and learning
how to query the data directly (rather than going through the incomprehensible
Geographic Information Systems [GIS] software).
Imagine my surprise
when one of the main presenters was my old student and much respected
colleague, Ramón Arrowsmith! Turns out he is one of the co-PIs of this project
and has used this type of high-resolution data in his study of active faulting
all over the world. I guess you could call him a tectonic geomorphologist, now
turned into a high-tech guru of LIDAR, Structure-From-Motion, and anything else
that can be used to study small but significant changes in land topography. Ramón
did his undergraduate at Whittier College, when both Dallas and I were teaching
there, pursued his study of tectonic geomorphology with Dallas, and eventually
became one of the luminaries in that field.
So what can you do
with high resolution topographic data? Well, for one you can figure where you
are and the elevation of the ground below your feet (which is what me and my
students are interested in), but you can also measure the height of individual
trees and shrubs, calculate biomass, quantify the movement of sand dunes, map
the subsidence of the San Joaquin Valley, track the deformation of a landslide,
quantify stream erosion, and so many other things I would have never thought
about. When you get out of school it is hard to find time to learn something
new, but by sequestering myself I have been able to spend a whole day learning
about a fascinating new area of earth and planetary science. I am happy 😊
Then again, a day
spent at home is like a day spent in Turlock, so I let my fingers do the
walking and tomorrow at 6 am I will depart for La Rochelle, on the estuary of La
Dordogne, and will bring my bike along for two days of exploration on one
of the great estuaries of France.
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