PSN-L Email List Message

Subject: Re: Modified sound card and datalogging and geophones
From: Gordon Couger gcouger@..........
Date: Thu, 21 Jul 2005 13:21:01 -0500

Hi   Chris,
 >     I understand now. We used chains of hf geophones and a 
 > hammer.... Sure you need te position accurately as well. Do 
you use
 > relative GPS to give you accuracies down to a few cm?

I haven't so far. The precision of the seismic data is not that 
good. But I will leave temporary bench marks I can find. Since 
it is being farmed no till I can bury a piece of tinfoil and put 
up a PVC post. If the post gets knocked down a GPS and metal 
detector will get me back on the spot. The PVC won't hurt any 
equipment it happens to go through.
 >     Almost everything I work with has a GPS. I did the first 
 >     units for and all the software for 
spryer in
 >     Interesting, but availablily depends on the roots being 
able to find
 > nutrients and hence on the rainfall & intensity. It probably 
would not
 > work too well for things like moss and poor land grasses. The 
grab every
 > nutrient molecule going and store them. This was the problem 
in Finland
 > after the Chernobyl nuclear disaster. The grasses and moss 
which fed the
 > reindeer heards soaked up most of the radioactivity.

It works for anything we have tried it on. It measures  the 
nitrogen in the leaves of the wheat by looking at the ratio of 
narrow band of red and near infrared light in late winter just 
before it starts the process of going from  vegetative state to 
a fruiting or grain producing stage. In this case we are adding 
fertilizer to the soil in the late winter because in the 
vegetative state wheat uses nitrogen to grow large lush leaves 
and in the grain producing stage it uses much more of it to make 
grain and much less to make leaves. Also nitrogen is some what 
perishable and can leach down below the root zone if there is 
too much rain or turn into ammonia and escape in atmosphere if 
water stands on the ground. So it takes less nitrogen to produce 
a bushel of wheat if it put one in February than if it is put on 
in the previous September. By putting it down in February or 
March we can assure that the nitrogen in the root zone where the 
plant can get it when it can make the most use of it. The 
fertilizer could just as well be foliar fertilizer that is taken 
up trough the leaves. In the case of most farm crops that is not 
an economic option because until you get rain the plant can't 
benefit from the fertilizer unless the ground is wet enough to 
take up the fertilizer.

We found several strategies that gave more return on the dollar 
spent on fertilizer, First was to make the nitrogen level in the 
wheat as near the same everywhere in the field as we could. The 
generally cut the fertilizer use in half and the dyed didn't 
change. The next was leave the areas high in nitrogen alone and 
double up on the low spots. That used the same amount of 
fertilizer and increased yields 7%. If we added in the 
historical yield data and added fertilizer to the point that 
each area had enough nitrogen to yield it full potential we got 
about 10% increase. I would be surprised it the system if half 
as could as it could be with smaller sample sizes and more 

This only works with nutrients such as nitrogen, zinc and few 
others that can be applied to a growing plant and still benefit 
it. Other nutrients phosphorus being the most important one need 
to be applied before the plant spouts and immediately available 
to the roots. In the case of Chernobyl strontium 90 is 
metabolized much like phosphorus and cesium is handled like 
potassium. So after the rain washed the fall out off the worst 
problme weren't probably seen until the next year and they did 
make an effort in some areas to deep plow the fall out under 
below the root zone of the grasses and fertilize with P and K to 
prevent the grasses from taking  up as many radioactive isotopes 
as they could. That only worked on land that could be plowed and 
that is not were reindeer generally graze.

 >     I agree they are power hogs and take a lot of resources 
for time
 >     for seismic senors that VLF will do just as well as GPS. 
I have
 >     seen jitter on VLF from WWV in a really bad magnetic 
storm but
 >     not as often as I have lost lock with the GPS.
 >     I don't get this problem at all often. The computer looks 
for an
 > interference free minute every half hour and then adjusts the 
 > crystal oscillator offset on the 59 mean pulses. The drift is 
 > set at less than 5 ppm and can be maintained down parts in 10^8

The problem is not very common it takes a really big magnetic 
storm to cause it an they don't happen often.

The 5 volt one Hz signal off a Rockwell Jupiter or many other 
GPS receivers makes an ideal heart beat for a clock for an 
microcomputer. If you need finer granularity a divider or phased 
locked loop on the 100 kHz output is a bit harder to build but 
is easier than a VLF radio.

Both your way with WWV VLF and a GPS have their place. But with 
GPS receivers with one second clock pins selling for 25 to 50 
bucks new in the box it is hard to see why any one would go to 
the effort to use VLF unless there were problems that precluded 
using a GPS.



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