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Ice rafts not sails: Floating the rocks at Racetrack Playa, Paper by Ralph Lorenz et. al.
ngunn
post Dec 29 2010, 06:04 PM
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Thanks once again to Jason B for making this intriguing paper accessible to all: http://barnesos.net/publications/papers/20...track.Rafts.pdf
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ElkGroveDan
post Dec 29 2010, 06:18 PM
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Fascinating paper Ralph. This is one of my favorite geologic topics. I've often pondered methods to observe this or even "catch" one in the act.


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djellison
post Dec 29 2010, 07:11 PM
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I must get up there and Gigapan the place. It's a bit of a trek off the road but I think two Gigapans 12 months apart could be really interesting!
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ElkGroveDan
post Dec 29 2010, 07:14 PM
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I suppose others have already thought of solar powered web cams and things like that. Though it seems that we are looking at movement during periods of partial immersion where the rocks may be barely visible from above.


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rlorenz
post Dec 29 2010, 10:44 PM
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QUOTE (ElkGroveDan @ Dec 29 2010, 02:14 PM) *
I suppose others have already thought of solar powered web cams and things like that.


yes.

Took a long time to get a permit but it can be done subject to certain Parks Service
limitations.

Since winter is the time of interest, and cameras cannot be left on the nice flat playa
itself, solar power is less effective than it might be, but digital timelapse cameras can
run on alkaline Ds for months.
http://www.lpl.arizona.edu/~rlorenz/timelapse.pdf

One would have to be very lucky to see the rocks move, but timelapse has been proving
useful to understand the conditions on the playa (how often flooded, how often frozen etc.)
That work is being written up right now.

btw, I believe someone has been doing Gigapan surveys of the playa for a year or so. I
tried a Gigapan myself but it drained the batteries in minutes and was overall rather
frustrating.
Having been going to the playa a couple of times a year since 2006, I've found walking
around and doing manual pans from GPS-fixed locations to be a very time-efficient means of
survey. Just wish the bastard rocks would actually move.
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ElkGroveDan
post Dec 30 2010, 12:21 AM
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Reading your paper Ralph it looks like the occurrence and duration of ice is still being debated. Have you though of getting permission to bury a couple of temperature sensors just below and/or at the surface of the soil to record long term temperature profiles? Also, have you tested the water seasonally for saline content?


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rlorenz
post Dec 30 2010, 01:22 PM
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QUOTE (ElkGroveDan @ Dec 29 2010, 07:21 PM) *
Reading your paper Ralph it looks like the occurrence and duration of ice is still being debated. Have you though of getting permission to bury a couple of temperature sensors just below and/or at the surface of the soil to record long term temperature profiles? Also, have you tested the water seasonally for saline content?


The subsurface temperatures are not of particular interest. We do have measures of air and surface temperatures nearby, though.

360 days of the year, there is no water. I imagine it would basically be fresh, as it runs off the hills. You don't see
much, if any, salt encrustation (unlike at Badwater or Devils Golfcourse) - it's all clay.
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PDP8E
post Dec 30 2010, 08:29 PM
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Ralph,
Thank you for that fascinating paper!
Cheers


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nprev
post Dec 31 2010, 01:48 AM
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Real blue-sky suggestion here, but would putting little RFID tags on the roving rocks be at all useful? What I'm thinking here is some way to obtain motion measurements (and, ideally, the rate of motion) without continuous human observation. If you had two RFID receivers plus recording and/or a remote telemetry hookup, presumably you could track 2D motion of the rocks 24/7/365.

Downsides:

1. This don't sound cheap (but there might be el cheapo ways to do it. I'm aware of the technology, just not conversant in it, but I do know that there's considerable commercial interest & concurrent development ongoing for logistics applications.)
2. Adding mass to the rocks might affect their behavior, even though this might be as little as a gram.
3. You might need more electrical power than I realize to keep an RFID interrogator running continuously, and it could be a royal (and expensive) pain to do fixes, maintenance, etc.



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Julius
post Dec 31 2010, 09:30 AM
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i've just seen a programme on weird or what>? must have been discovery channel
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Juramike
post Dec 31 2010, 01:43 PM
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QUOTE (nprev @ Dec 30 2010, 08:48 PM) *
remote telemetry hookup, presumably you could track 2D motion of the rocks 24/7/365.


LoJack for rocks? laugh.gif


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rlorenz
post Dec 31 2010, 01:50 PM
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QUOTE (nprev @ Dec 30 2010, 08:48 PM) *
Real blue-sky suggestion here, but would putting little RFID tags on the roving rocks be at all useful?


Things like that have been proposed, but I doubt it'd be that useful and I very much doubt that would
be permitted. Research activities that disturb the visual appearance of the playa are forbidden.
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ZLD
post Dec 31 2010, 04:59 PM
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QUOTE (nprev @ Dec 31 2010, 01:48 AM) *
Real blue-sky suggestion here, but would putting little RFID tags on the roving rocks be at all useful?


The issue I would see with RFID is that you would have to triangulate the position to track the motion. I'm not sure how far the stones have gone in a single move but if it is significant enough, it can make it difficult to get a good read on the tags. Usually the range is maxed out at around 9 meters, 20 if you use a parabolic dish on the reader. I would suggest using a micro three axis accelerometer (found commonly in smartphones) with a really small FM transmitter to transmit the output.
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nprev
post Jan 1 2011, 09:44 PM
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Hmm. Got it, Ralph.

Well, let's see: How about a small ground radar or sonar system? The analog here is the radar that major airports use to monitor surface movements of aircraft. This would be non-invasive for the playa.

A few of the admittedly many challenges are:

1. Available power (always).
2. Commercial availability of suitable equipment; might need some pretty high-freq stuff to get useable returns from small targets like those rocks.
3. Look geometry/suitable siting: You'd probably need to set it up on a small hill or rise to look down on the playa.
4. $$$

Hope you don't mind the goofy suggestions. It's an interesting problem to contemplate!

EDIT: Re RF hazard (if radar was selected), the good news here is that most modern equipment has very low peak power output compared to older systems. The innovation driving this has been improved receiver sensitivity & selectivity; radars don't have to blast out nearly as much energy as they once did.


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djellison
post Jan 2 2011, 01:44 AM
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QUOTE (ZLD @ Dec 31 2010, 08:59 AM) *
I would suggest using a micro three axis accelerometer (found commonly in smartphones) with a really small FM transmitter to transmit the output.


That's out.

QUOTE (rlorenz @ Dec 31 2010, 05:50 AM) *
Research activities that disturb the visual appearance of the playa are forbidden.



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