planetwater

ground- water, geo- statistics, environmental- engineering, earth- science

ssh fun

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I have setup a raspberry pi as a measurement computer. Now I can access it

a) on my Mac by mounting a directory, using SSHFS 2.5.0 via

sshfs -o volname="<MOUNT_NAME>" <USER>@<IP_ADRESS>:<directory_on_raspberry> <directory_on_my_mac>

b) on my iPad! I use OpenTerm to ssh into the machine, run scripts, and I use ShellFish (currently in beta) to basically mount the directory with the output into the file system (I mean into the Files App) on my iPad.

Whoooopeee!!

Written by Claus

June 14th, 2019 at 1:41 pm

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Starting a New Blog

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I had linked to a post by Peter Rukvina’s last time. I am doing it again – this time he linked to Rosie, who started a blog in 2019 called “press pound”.

I can’t applaud Peter’s comment enough:

I’m happy to see the corner turn from “why did blogging die when we loved it so?” to “I’m going to start a new blog!”

Written by Claus

June 11th, 2019 at 12:57 pm

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Moving to Personal

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Since I while I have a new job at the Research Facility for Subsurface Remediation (VEGAS) at the University of Stuttgart (link to newly setup webpage and twitter presence). I’ve been thinking about it for a while and came to the conclusion that both this blog and the associated planetwater twitter presence will move to more private conversations, although still associated to water.

As a first, I want to give a shout out to Peter Rukvina at ruk.ca. There is a lot of talk about a renaissance about the open web. A renaissance of RSS. A renaissance of blogging. Peter has been there since before I started to be there — and he is still there, stronger than ever! His recent post, My Own Private Underhay, is an orbitruary on surface. Really, he is laying out his way of life. He boils it down to this:

What I have started to do, in my daily life, is that when I’m faced with small forks in my road–take the car or take the bike? watch TV or join a committee? have a nap or call my mother? order pizza or learn to make pizza? –- I will take the fork that, while it might be a little harder, require a little more effort, might take me out of the realm of things I’m comfortable doing, is the fork that’s best for my family, my community, and the planet.

I encourage everyone to go to Peter’s site and check out his humanitarian- printing- open- (source) and overall kind- ness!

Written by Claus

May 20th, 2019 at 4:20 pm

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Ein Regengenerator der anderen Art… nicht multi-site und nicht vektor-autoregressiv, aber trotzdem schön… 🙂 https://rainbowhunt.me

Written by Claus

January 3rd, 2019 at 11:13 am

Posted in pw.micro.blog

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Hello World from micro.blog!

Written by Claus

November 8th, 2018 at 11:12 am

Posted in pw.micro.blog

come to AGU18 session “H114: Space-Time Data and Models”

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I would like to invite you to the following session at #AGU18:

The problem of estimating a variable at unobserved locations and/or times is important for many areas of research, including geosciences, civil-/ environmental engineering, soil sciences, agriculture, ecology, forestry, meteorology / climatology, oceanography, health / epidemiology.

The amount of data gathered is increasing (e.g., advances in measurement technologies, remote sensing, or citizen science). Challenges remain related to the interplay between heterogeneous measurements and improvements in models that can make use of the various types of data. This session aims to bring contributions together that demonstrate how to improve datasets and maximise their use through measurement techniques, statistics, and modelling, e.g., via

  • innovative ways to measure data in the environment;
  • the incorporation of innovatively measured data into modelling (usefulness, relevant scale);
  • the inclusion of as much information as available to improve prediction (secondary / heterogeneous data, data on different scales);
  • the consideration of the variability in the quality of the measurements;

Please find a pdf about the session here.

(cross-posted from claus-haslauer.de)

Written by Claus

July 30th, 2018 at 4:41 pm

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How to Filter a List in Python; also: how to compare two results of %timeit

Written by Claus

May 16th, 2018 at 9:02 pm

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Breaking Twitter?

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Twitter might soon be broken (#BreakingMyTwitter). Really, third party clients might be broken, due to API changes. More details are available at apps-of-a-feather.com, a website from a group of third party twitter clients.

I am happy with Twitterrific, both on the mac (both before and after the revival) and on iOS. I have never used a native twitter client on any OS. I am not sure since when it is known that the end of the third party clients could be near. Version 5 of Twitterrific has been out since October 2017. Was it known then?

Now, as I have posted before, I appreciate the free web. The existence of this website is evidence of this. I guess, a lot of things can happen until June. It would be nice if open alternatives (e.g., micro.blog, mathstodon) would gain more users. On the other hand, on work-related topics, it seems like Twitter has recently stepped over a critical mass threshold, and I do enjoy the conversations there. Yet again, I know people who leave twitter, because of trolling and because of being not open. As they say, the future remains interesting!

Written by Claus

April 9th, 2018 at 8:05 pm

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Getting Ready for #hymod18

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To get ready for the “Integrated Hydrosystem Modelling 2018″ Conference”s, about to start in a couple of hours, I played with a watershed on my sofa and a bivariate Gaussian distribution on my coffee table

Both apps are enabled via Apple’s ARKit:

  • GeoGebra has an app called “GeoGebra Augmented Reality” that allows you to plot functions of two variables on a surface that you can pick, like my coffee table. You can then rotate, walk around it, look on top of it and explore in other ways those functions. Great fun!
  • The WWF Free Rivers app puts a simple watershed on a surface you can define (like my sofa). Then clouds move in, and you can paddle down the river. Maybe more for kids. Still fun.

Great to see such nice use cases, and let’s get ready for integrated hydrosystem modelling #hymod18!

A watershed on my sofa
A watershed on my sofa.

a bivariate Gaussian density function on my coffee table
A bivariate Gaussian density on my coffee table.

Written by Claus

April 3rd, 2018 at 6:48 am

Posted in Uncategorized

Crisp and Interval-Based Conditional Probabilities

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“Censored data” is the common statistical term for values that are within an interval. A typical example from environmental data-sets are measurements below a certain detection limit. If a measurement is below detection limit, due to the analytical performance of the device that measures the concentration, we don’t know its precise value, but we do know that it is somewhere in the interval \smash{\in(0, \textnormal{detection limit})}.

Application in Environmental Hydrology

A typical example where censored measurements play an important role are solute concentrations in groundwater. The measured concentration value of some solute depends on the analytical method that was used for quantification of the concentration. Sometimes, the concentration is so small that we can not be certain about it’s value, and we assume that the true value is somewhere between zero and the analytical detection limit.

In a recent example, my coauthors and I demonstrated the importance of including censored measurements to derive a representative concentration of chlorinated solutes in a hydrogeological layer at two boreholes within a fractured sandstone. Due to the fractured nature of the sandstone, at most depths the concentrations were fairly small and frequently below detection limit, whereas in the fractures, typically large concentrations were encountered. Taking the censored measurements (the concentrations below detection limit) in a statistical meaningful way into account lead to an estimate of representative concentrations that corresponded to the conceptual site hydrogeological model at the upstream and downstream borehole, and can be important for site assessment.

Related to censored measurements, but different, are true zeros. An example of a measurement of true zero is a rain gauge that measures precipitation when it does not rain. The distinction between a true zero and a measurement below detection limit can be tricky, because they are both small values. If you’re interested in how to include true zeros in this approach, please continue to read here. A truely zero measurement means that its value is zero and not in an interval between zero and the detection limit.

If you are interested in a statistically reasonable treatment of censored measurements, you can find the related publication in Environmental Science and Technology.

I’ll explain the basic underlying theory below.

Basic Statistics Example

I have written about conditional_probabilities quite some time ago. This can be viewed as an extension.

A crisp condition is something like “what is the probability of event A to occur, given event B has occurred”. This is how conditional probabilities are typically taught with. Compared to a univariate density, a conditional density should have a smaller variance, and is shifted towards the condition. So far so good.

It turns out that there is a “not-crisp” condition. This is something like “probability of event A given that ‘event’ B is somewhere between zero and b”. The funny thing is, that the uncertainty about this event to occur is smaller than a corresponding normally-distributed univariate event.

When looking at the figure below, this means:

  • the yellow line indicates a standard (variance=1) normal Gaussian density
  • two crisp conditional densities are shown by the solid (p(x|y=-2.0)) and the dashed (p(x|y=+2.0)). Both those densities have a smaller uncertainty (variance) than the univariate standard normal
  • two interval-based conditional densities are shown in red (p(x|y \leq -2.0)) and blue (p(x|y \leq +2.0)). The interval-based densities have the same location as the crisp conditionals. Their uncertainties are smaller than the corresponding univariate, but larger than the crisp conditionals.

Total rho0 7 sym 2 00

Written by Claus

March 28th, 2018 at 8:45 pm

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