As can be read in the pre­vi­ous blog post­ing, I have now some weather data around. Here the header from the CSV file I gen­er­ate out of the XML file of the soft­ware:

Date;Humidity (room);Temp (room);Humidity (out);Temp (out);Pressure (abs);Wind (ave);Wind (gust);Wind (dir);Rain

Cur­rently I pro­grammed the weather sta­tion to save the data every 5 min­utes. The long-term goal is to decide if a given wind tur­bine deliv­ers a sane amount of energy (dur­ing a com­plete year) at a given place. As I do not want to wait that long to get some infor­ma­tion out of this, the ques­tion arises, what I can do with this weather data?

Here an exam­ple of the out­put (ignore the rain and wind val­ues, the sen­sors are not attached at a place where there is wind or rain, the com­plete set is hor­i­zon­tally on the floor instead of ver­ti­cally how they are sup­posed to be; and do not be shocked about the room  val­ues, it is the “server room” in the basement):

2010-09-02 12:55:01;52.0;18.700;30.0;27.000;978.600;0.0;0.0;135.0;4.200
2010-09-02 12:50:01;53.0;18.700;30.0;27.500;978.600;0.0;0.0;135.0;4.200
2010-09-02 12:45:01;53.0;18.600;30.0;27.300;978.500;0.0;0.0;135.0;4.200
2010-09-02 12:40:01;53.0;18.600;30.0;27.800;978.600;0.0;0.0;135.0;4.200
2010-09-02 12:35:01;53.0;18.600;30.0;27.700;978.500;0.0;0.0;135.0;4.200
2010-09-02 12:30:01;54.0;18.500;31.0;27.500;978.700;0.0;0.0;135.0;4.200

Some things I came up with myself:

• A line-graph of the val­ues dur­ing a day/week/month.
• A graph of the amount of accu­mu­lated rain per hour/day/week/month/year.
• The aver­age temperature/humidity (as an error bar, so see the min/max too) per day and night, but what to use as the times where the day starts/ends? I would like to have the day-part cover the real day­light time (minus some ramp-up and ramp-down time), but I do not have any idea how to get this for each day and for my region.Does it make sense to do the same per hour (with­out any ramp-up/-down)?
• Does the com­bi­na­tion of tem­per­a­ture and humid­ity and maybe wind tell some­thing? If yes, how to com­bine them and how to inter­pret the result?
• Sim­i­lar for the pres­sure. I do not know what it tells me, but in a graph I can maybe add some hor­i­zon­tal lines which tell some­thing (rain prob­a­bil­ity and maybe dan­ger zones?).
• For the wind speed the instruc­tion man­ual comes with a nice table of the beau­fort scale and a cor­re­spond­ing descrip­tion. This can be put into some col­ored hor­i­zon­tal lines which show more or less dan­ger­ous speeds.

For the plot­ting of the data, I intend to use gnu­plot with the CSV data as the input. It should allow me to auto­mate a lot of things, and some of the graphs should also be easy to real­ize inside gnu­plot itself with­out any exter­nal pro­cess­ing, the ques­tion is only how to real­ize it. For exam­ple for the aver­age of some val­ues I do not know if it makes sense to use some­thing else than the arith­metic mean.

A while ago a wind tur­bine was installed not far away from my place. It is far enough to not dis­turb us, and it is near enough to notice that it turns a lot (IIRC I have seen it only once not turning).

This trig­gered a ques­tion. How much energy would such a device (smaller of course) pro­duce at my place?

The answer depends upon sev­eral fac­tors. The wind speed, the wind direc­tion and the wind-speed-to-power-output curve of the device. If you do not take a device which rotates around the hor­i­zon­tal axis but the ver­ti­cal axis, the wind direc­tion can be taken out of the ques­tion (prob­a­bly not com­pletely, but to answer my ques­tion this sim­pli­fi­ca­tion should be ok). The output-power curve depends upon the device, and I hope it is easy to get it from the ven­dors. The remain­ing open ques­tion it the wind speed at my place. Is there enough wind with enough speed?

To answer this ques­tion I bought a weather sta­tion with an anemome­ter (wind speed sen­sor). I searched a lit­tle bit until I decided to buy a spe­cific one (actu­ally I bought three of them, some cowork­ers got inter­ested too but they found only much more expen­sive ones, so soon there will be three more weather sta­tions in use in Bel­gium, France and Ger­many). The main point is, I can con­nect it to an USB port of a PC and there is some soft­ware for Linux to read out the data. It also comes with some other outdoor-sensors (tem­per­a­ture, rain, wind direc­tion, humid­ity, …) and an indoor-control-unit with some inter­nal sen­sors (tem­per­a­ture, humid­ity). The user inter­face is mainly the touch­screen of the control-unit. There is also some Win­dows soft­ware, which is needed to pro­gram the inter­val in which the mea­sure­ments are taken and saved in the control-unit.

It seems the weather sta­tion is pro­duced by Fine Off­set Elec­tron­ics Co.,Ltd and sold within dif­fer­ent brands in dif­fer­ent loca­tions. The Linux soft­ware can read all of them, as the ven­dor and prod­uct IDs are not changed.

Port­ing the soft­ware was easy, it uses libusb and I just had to cor­rect a lit­tle prob­lem for the non-portable func­tions which are used (I asked about them on usb@ and the response was that they just got imple­mented upon my request and will be com­mit­ted to HEAD soon). I made a lit­tle patch for the soft­ware to only use them when avail­able (if you have not loaded the USB HID dri­ver, you do not need to care about them) and com­mit­ted it to the Ports Col­lec­tion as astro/fowsr.

Now I just need to attach the out­side sen­sors at the place where I would put the ver­ti­cal axis wind tur­bine, install some toolkit which takes a series of mea­sure­ments and dis­plays them as a nice graph (while keep­ing all data val­ues) and write some glue code to feed the out­put of fowsr to it. After a year I can then cal­cu­late how much power a given wind tur­bine would have pro­duced dur­ing the year and cal­cu­late the return of invest­ment for it.

The Linux soft­ware also ref­er­ences sev­eral weather sites, for some of them you can get even an iGoogle wid­get so that you can view the data from wher­ever you want (as long as you have a suit­able inter­net con­nec­tion). I think this is also some­thing I will have a look at later.

Note to users in Europe, the device also comes with a DCF77 receiver. As the time is dis­trib­uted in UTC+1 (or +2, depend­ing on the day­light sav­ing time), you should adjust the time­zone set­ting accord­ingly to this, not to plain UTC (so for me the time­zone should be ‘0’ for the same timezone).

Before I have read the news feeds I am inter­ested in via the Fire­fox plu­gin “brief”. It did all I wanted it to do, but I had all the data and meta­data (all the feeds and read items) only in one browser. I was not able to have a shared state at work and at home.

Now I installed rnews on my web­server. It is multi-user capa­ble, so that mul­ti­ple peo­ple can read the feeds they are inter­ested in, with­out the need to have mul­ti­ple instal­la­tions. I can use it from any place where I have an inter­net con­nec­tion, with­out los­ing the state.

It is in the FreeBSD Ports Col­lec­tion as www/rnews.

I merged the v4l trans­la­tion layer into the lin­ux­u­la­tor of 8-stable. As in –cur­rent, this just means that linux apps (like Skype) can now use FreeBSD native devices which con­form to the v4l ABI. The port multimedia/webcamd pro­vides access to some web­cams (or DVB hard­ware) via the v4l ABI.

Peo­ple which want to test the lin­ux­u­la­tor part should first make sure a native FreeBSD appli­ca­tion has no prob­lem access­ing the device.

I got noti­fied that my blog was not acces­si­ble for a while. Seems that at least recent fire­fox ver­sions some­how changed their behav­ior in what is send in the HTTP-header. This caused an Apache Redi­rect­Match rule to trig­ger, which denies access to some parts of the blog for some users.

The WP-login, WP-dashboard, and logged-in users where not affected by this, so if you have some cus­tom rules which deny access to your blog, make sure you make a test of your blog when logged-out.