Monday, July 14, 2014

ArduBoat: modifying a low-cost RC boat for aquatic auto-piloted missions

In our fieldwork on Rapa Nui, we have been interested in locating points where freshwater seeps out of the groundwater table into the ocean as these areas appear to be significant features of the prehistoric landscape.  There are a variety of ways in which we have done this work — thermal mapping, conductivity measures, temperature profiling and so on.  Recently, we used a kayak to measure changes in conductivity and temperature along the shore (dragging a level logger). It occurred to me, of course, that robots might make a more systematic survey than what we can do in a kayak in that they could run in consistent transects along the coast in parallel lines. We could then run the transects over and over at different tidal heights and match the survey with thermal quadcopter runs.  Naturally: Robots Do It Better (tm).  In this way we can get spatially consistent measurements that are be well suited for locating discrete spatial features associated with freshwater. We use aerial drones for mapping - why not a water based floating version?

So this thought train has led me to test out the practicality of a simple robot boat that I can test out on Catalina.  Of course, there lots of folks who have made versions of RoboBoats (or Arduboat https://www.youtube.com/watch?v=ogQsaIHyJnk) - this is not a new idea.  For me (lacking shipping building skills) much of the challenge appears to be simply making a boat that is suitably shaped with the various props and so forth. 

Boat

While at Harbor Freight, I came across a radio controlled boat that seemed like it might be ideal for modifying into a robot boat. http://www.harborfreight.com/radio-controlled-speedboat-95641.html  This reasonably inexpensive ($50) RC boat runs on two electric motors that are controlled with a simple speed controller/RC interface. What is potentially ideal about this boat is that it is steered by two props — no need to have a rudder. This configuration is similar to the “tank” configurion in the ArduRover where steering is accomplished by two wheels (http://rover.ardupilot.com/wiki/setup/) In addition, for this boat the sizes of the motors appeared similar to brushless motors I’ve worked with on multicopters.  With some changes to the motors, the addition of a speed controller (ESC) and the APM autopilot, it seemed like a relatively simple conversion.  

NewImage

As I wanted to make the boat use the same basic configuration as an ArduRover, I purchased two brushless inrunner motors that are the same diameter and length as the original ones (http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=42448). I addition to size/configuration, I picked these motors out of a large number of possibilities basically on price alone. I am entirely unsure what configuration I would want for a boat motor but these motors were cheap enough to use as a start.  I used two 30  amp ESCs I had laying around from a multicopter (http://www.hobbyking.com/hobbyking/store/__2164__TURNIGY_Plush_30amp_Speed_Controller.html) I am certain there is probably a better ESC configuration for a boat (one that does reverse?), but this is what I had available. Finally, used a 4 channel RC controller ($24) http://www.hobbyking.com/hobbyking/store/__8338__Hobby_King_2_4Ghz_4Ch_Tx_Rx_V2_Mode_2_.html  and, of course, a 2.6 APM Ardupilot (https://store.3drobotics.com/products/apm-2-6-kit-1). Using a LiPo battery with an XT-60 connector and the APM power module (https://store.3drobotics.com/products/apm-power-module-with-xt60-connectors). 

Following the instructions here (http://rover.ardupilot.com/wiki/setup/) but corrected to suit my Mode 1 receiver (I should probably use a Mode 2 but since Im not planning on manually driving the boat, it shouldn’t matter), connected the in this way:

RC receiver          —>  APM Autopilot Input

Channel 3   ->            3

Channel 4  ->             1

Channel 5  ->            7

Channel 6  ->             8

 

On the output side, I connected the ArduPilot output in this way:

ArduPilot Ouput      ->  ESC

1     -> ESC on port side

3     ->  ESC on starboard side. 

Here is what I have so far:

Photo 2

 What is still missing is the telemetry link to allow the boat to update the ground station with position information (Ill use the 3DR radio set: https://store.3drobotics.com/products/3dr-radio) and the GPS (https://store.3drobotics.com/products/3dr-gps-ublox-with-compass). While I have the GPS, I need a new cable that is longer so I can attach it onto the bow of the boat.  In essence, both of those are basically plug and play. The radio is powered via the APM and the DF13 connector. 

Physically, the motors fit right into the existing motor mounts.  The shaft of the new motors has a slightly great diameter than the original ones so I had to drill out the coupling part (which is plastic) so that it would fit. 

On the APM side (using Mission Planner) you need to configure the APM to use “Skid Steer” — a vehicle with dual throttle steering (like a tank). This is done by altering the APM parameters (see: http://rover.ardupilot.com/wiki/apmrover-loading-the-code-and-setup/)

Skid Steer Functions:

  • Skid Steer IN enabled (set to 1) sets up the APM to control a Skid Steer vehicle with a dual throttle skid steer transmitter.
  • Skid Steer Out enabled (set to 1) sets up the APM to control a Skid Steer vehicle with a conventional single throttle RC transmitter.

 

SKID_STEER_IN: DISABLED Set this to 1 for skid steering input rovers (tank track style in RC controller). When enabled, servo1 is used for the left track control, servo3 is used for right track control
SKID_STEER_OUT: ENABLED Set this to 1 for skid steering controlled rovers (tank track style). When enabled, servo1 is used for the left track control, servo3 is used for right track control

 I’ve done some basic tests and it seems to work as least in principle. I’ll need to get the GPS cable before I can do an real tests with the mission planning. Also, Im not sure how long the battery will last or how to tune the motors to get appropriate RPMs (right now the motors spins like a multicopter — and would rocket across the lake). But so far so good!


Monday, April 28, 2014

Archaeology Blogging (and Publishing)

The bloggers for the 2014 “Archaeology Blogging Carnival” were asked a final question about the “future of archaeology blogging” (or something like that). As I’m currently stuck on a plane to Austin, I thought I’d summarize some of the thoughts that I have on the topic and use this post as an opportunity to explore more general aspects about publishing.

First, I think blogging has the potential to facilitate academic discourse leading to some a degree of scholarly “activism" within the discipline. While traditional journals serve as broadcast mechanisms, we have few ways of carrying on cross-university conversations outside cramped poster sessions or random encounters at the bar in the yearly meetings. We need social network and the generation of media to create grassroots effort to make a number of changes.  PLOSOne is one venue that creates a platform for some limited feedback through its inline comment feature but archaeology is not the journal’s primary focus.  While blogs are still broadcast oriented, they encourage feedback in the comments that can contribute to debate and idea exchange.  

It is clear to me from the recent SAAs that we need more debate our our discipline. While polemic is tiresome and often pointless, we need everyone to continue to challenge each other in a positive way to improve the work that we do. If our goal is to do archaeology as a science then we need to think deeply and carefully about how we construct our observations to produce explanations. It is easy to get complacent or to slip into common sense thinking given the implicit nature of our own common sense. We need to call each other out on sloppy thinking, poor use of reasoning, and botched analytic applications. This criticism need not be Flannery-esque (and other like him) name calling though I suppose some of that goes with the territory. But as a discipline we are much richer and and productive when we are explicit in our thinking about what we do and when we tease apart the often implicit relations between our ideas and the empirical world.

Such clarity has been increasingly difficult to find in our discipline. I find that some of the “Processual Plus” mindset of the past 15 years has led a large part of the discipline to simply accept everything that everyone does as satisfactory: it's all under the big tent. But “inclusive” archaeology need not be “sloppy” archaeology nor does it necessary have to include simply any random idea that people cook up. Discussion provides a process by which ideas can be shaped and honed. Blogs, I believe, could be a significant part of that process.   

Most blogs, I think, are going to have visibility largely within academia while a few will reach a more public audience: so much of what we actually do as an archaeologist is obscure and tedious for the lay person. But that is fine. It is the day-to-day work that has the most to gain from the informal and interactive form of communication that constitutes blogging.  

And when we speak to each other, we all have the potential to affect larger change. As a way of an example, I would like to focus a bit on publishing in archaeology. Aspects of blogging overlap quite a bit with publishing (or should) as both are means of sharing information that we generate (one in a formal episodic way, the other in an informal continuous fashion.) I believe that we are long overdue for a change in the way we (as academics) consider places to publish and choose the journals for which we do reviews. This need comes from recent changes that have taken place in publishing as well as in academia. In terms of the publishing, the industry as a whole is struggling to find a way of doing business. Much of their existing models and practices depend upon dead-tree media and the capital machinery required to produce physical copies of articles. Publishers used to print books and journals and these required physical infrastructure and major investment. As academics, we did our share of the work: we generate the ideas, produce the writing, review the work of others.  Both sides of the publishing world were enriched. The publishing world used to ‘work' on the basis of mutually beneficial activities. 

A couple of things have changed with regards to this scenario. First, commercial publishers have grown fewer in number and the surviving journals have been consolidated into multi-national mega corporations.  These companies pay their CEOs and shareholders millions of dollars by charging individuals libraries skyrocket high rates.  For the few companies that control 95% of the academic journal, publishing is an exceedingly lucrative business. The CEO of Wiley and Sons, Stephen Smith, makes over $5MM a year (http://investing.businessweek.com/research/stocks/people/person.asp?personId=23627960&ticker=JW%2FA) Erik Angstrom, CEO of Elsevier took home $7.5MM (http://www.theguardian.com/business/2013/mar/12/reed-elsevier-chief-engstrom-pay) These companies are generating record profits on the backs of publicly funded research , subscriptions taken from public funded libraries, the labor of academics who are working for low pay while handing over copyrights, and by prohibiting sharing of ideas that were paid for by taxpayers. They oppose self-publishing and open access — anything that might eat into their massive profits. And this is true of AAAS’s Science and Macmillan’s Nature, the two most prominent science journals in the world (http://synapse.ucsf.edu/articles/2014/04/03/scientific-publishing-era-open-access). 

Second, the nature of the academy has dramatically changed. No longer do universities value the service faculty do for their disciplines.  The modern university is measuring bottom line one way or the other: impact factors, numbers of students graduated, numbers of classes taught per faculty, dollars raised and so on.  Worse, the numbers of faculty who are working outside of the tenure-track system continue to grow. These adjunct/affiliated academics ONLY make money on the basis of their teaching: they largely do research in their spare time with the hope of landing a job.  Non tenure track faculty now make up a staggering 76% of ALL faculty regardless of institution type (http://www.aaup.org/sites/default/files/files/AAUP-InstrStaff2011-April2014.pdf). These faculty simply have no incentive to participate in the process of reviews (much less publication). Even those that do have a tenure track job are being made to teach more so that ‘student throughput’ can be maximized as administrations become increasingly corporatized. While some of the gray-beard faculty still enjoy a relatively burden free teaching existence, the reality is that an ever-smaller proportion of faculty have any reason to participate in the publishing process except for the submission of written articles, a metric used for promotion. 

There are a number of actions that should become call to arms for archaeologists in terms of publishing (and blogging):

  1. We should publish open access whenever possible. The public paid for our research time. Every tax payer should be able to enjoy the products of this work. 
  2. We should publish in non-profit journal exclusively:  American Antiquity is run solely for the benefit of archaeologists through the Society for American Archaeology.  Antiquity is run by a non-profit (the new editor, Chris Scarre assures me that a new website will vastly improve the online nature of this journal). . Current Anthropology is funded through Wenner-Gren. These (and other) journals are not out to carve profits out of the public and the labor of poorly paid academics: they are there to benefit us through the distribution of the work we do to our colleagues and the rest of the world.
  3. We should cease donating our time reviewing articles for mega-profit commercial journals until they properly compensate us for our professional time. We shouldn’t be donating our (publicly funded) time for corporate earnings. If we do, that time should be paid - or at least some equal type of compensation be made such as student scholarship funds, open access or other kinds of community benefits. PeerJ, for examples, offers an open-access model which costs just the basic costs of the work required to get the work published — not giant million-dollar bonuses for CEOs.
  4. We should publicly archive all of our work and our data. ArXiv.org is an excellent place to archive pre-prints as is SSRN.com.  Our data should also be archived in publicly accessible repositories. With the explosion of cloud storage such archives are easily obtained at low cost even for relatively massive archaeological data sets (We should also refuse to play the “security through obscurity” game and make information about the record known so that everyone can participate in its preservation. The argument about secrets making good protection is not well supported by evidence.)
  5. Returning to the issue of blogging, we should blog as part of our regular communication between each other and with the public. We should preference and value all efforts that produce an impact regardless of venue and the “status” of the outlet.  A million-view blog with suitably professional content should have as much value (if not higher) than a published “comment” in a journal. Our mission should be about the generation and communication of knowledge about the past and we should reward anyone who achieves those goals in as many media as there are available. 

I suspect that some of these changes will happen regardless of what we do - they will just take longer. Pressure for open access publications already exists (e.g., the NIH mandate, the mandate by the UCs to have all faculty archive all publications).  Journals are in crisis mode since they cannot easily get reviewers. We are increasing our electronic presence each year (SAA even had a hashtag for the first time #SAA2014). Consequently, these comments may simply be one view into the future. The sooner we full grasp this new reality, however, the easier the transition will be.  

Wednesday, March 19, 2014

QGIS Tutorial Links

With the release of QGIS 2.0 (and greater), this open source project has become a serious contender for a full-blown GIS solution that covers nearly all of the necessary features found in ArcGIS but at a reasonable price (free!). I’ve started to use QGIS in all of my projects and am very pleased by its features and performance. Like all complex software, there is a learning curve but if one knows ArcGIS already most of it is fairly self-explanatory. I’ve started to assemble some tutorials that I can point students towards. Here’s the list I have to date:
I will add more to this list as I come across useful resources for learning QGIS.

Monday, November 25, 2013

Archaeology Blog Carnival

From now until the April 2014, I am going to be participating in the Archaeology Blog Carnival - “Blogging Archaeology”. From what I can tell, this is a bit of a meta- enterprise in which we write about the process/practice of writing about archaeology. Ill be interested to see how the questions evolve for I fear the degree of meta-ness may produce a bit of self-indulgence and navel gazing. I suppose, however, that the “carnival" provides a forum for folks who are blogging out there in the blogosphere to share some perspectives on their writing habits. We shall see. We even get a twitter hash to use: #blogarch.

The question for November is: Why blogging? – Why did you start a blog?

I began blogging mostly as an experiment and to see what all the hoopla about “blogs” was about. I certainly did not start writing to broadcast a specific message or to report on anything in a consistent fashion (as a review of evobeach.com will show you). From what I had read, the blog medium seemed to be a great way for sharing information and  as an academic, sharing has direct value. It is clearly beneficial to us to share information in as many media forms as possible as measures of academic success center around how many people share the ideas that one has originated (via citation analysis, for example). Of course, sharing is not the only property of value for ideas: they also have to accomplish something. If academics were all about sharing, science (at least) would be an enterprise that encourages Kardashianism rather than the generation of knowledge. While I know that in some areas of the anthropological realms sharing may be the only value held (I’m looking at you faux French philosophers), I choose to believe that knowledge ultimately trumps sharing by itself. Mendel clearly had the latter down but knew nothing about marketing, not that it mattered in the long run. The best situation occurs, of course, when both sharing and knowledge can be merged. The Mars missions, perhaps, are good examples of how the work of scientists can find its way into everyone daily informational lives. Of course, the value of the sharing can be maximized when the sharing occurs between professionals/academics since those individuals not only appreciate what we each are doing but have the opportunity to put shared knowledge into practice. But the value of sharing also goes to those who are just interested or simply wonder where tax dollars go.  

The blog world is just the tip of the iceberg in terms of new ways of communication. Give the rapidity of change in the way in which we share information, it behooves all professionals to become familiar with new media forms, if only to ensure that one's message has the best change of being heard. It remains fairly clear that dead-tree media still retains a core value in the academic world, but the degree of centrality is slipping rapidly as electronic media becomes a larger part of one’s research base (and the holdouts retire). Blogging is a way of exploring digital means of sharing with low cost and low overhead. 

Blogging also gives one a way of sharing ideas that ordinarily do not qualify as material for the standard range of professional publications.  Beyond just the yammering and sharing of groovy photos and whatnot, one can discuss technical details that are difficult to share in traditional academic media. For example, I just wrote about my work on building a multispectral camera based on Raspberry Pi (http://www.evobeach.com/2013/10/nir-raspberry-pi-camera.html). How one goes about building and tinkering with such a camera is not ordinarily material that is going to get a journal editor (at least in archaeology) particularly excited. Yet the technology (being inexpensive and opening doors to entirely new ways of studying the archaeological record) can be transformational. So blogging becomes a way of sharing this kind of information. 

In addition to being a platform for discussing technical details and geeky stuff, blogging is also an interactive platform. Individuals can respond to posts or pose public questions to authors that would otherwise be impossible. This interaction can lead to debates, clarifications, or collaborations — all of which mirrors the real kind of interaction that goes on within the closed doors academia but at a dramatically faster pace and with enormously expanded inclusiveness. No longer are some hand-picked crew the only ones allows to write critiques about an article (e.g., the Current Anthropology CA Treatment): everyone can get engaged with academic dialog (for better or worse). Given that the interaction is public (and not some private email chain) and  the publications are nearly instantaneous, the blogosphere opens new doors for enhancing information that exist in other formats (such as dead trees).  For example, I recently responded to a critic about our moai transport work and answered questions that were posed. I like to think that blogging such interaction enhances the value of the publications and contributes to make the ideas clearer.  



Sunday, November 17, 2013

Response to Comment

 

A Sophist wrote a comment in response to the blog entry Diamond attempts to defend myths of Easter Island: Lipo and Hunt respond :

My questions remain: 1. Were there Palm trees on Easter Island when the first Europeans visited? And if not, then H+L are arguing this was rats and not humans cutting the trees down? 2. If Palm Trees are unable to be made into canoes, how did the people make ocean going canoes? In there were no canoes, how did Dolphin get into the diet? I guess I am missing the problem. This seems to be a lesson in how isolated political leaders who do not feel the pain of their actions (cutting down the forest for whatever bloody reason: fuel, canoes, to move statues, etc) can lead their society to the brink of destruction. 

The questions themselves point to common but false assumptions often made about Easter Island prehistory and they are worthing examining. 

Question #1:  Palm Trees.  I’m not sure how the two different parts to the question are related (i.e., whether there were palm trees at contact in 1722 and whether rats “cut down” the trees). For the first question: no one knows exactly whether there living examples of palm trees on the island in AD 1722 when Roggeveen first arrived nor later in the 1770s when the Spanish and English arrived.  The overall impression we get from these early written accounts is that the island was largely devoid of trees though there are also mentions of “palms” in some of the descriptions.  The pollen and macro  botanical record is equally unclear given the relatively poor dating of the island as a whole and relatively few dates of palm nuts in particular. A major effort to date events on the island (with modern understanding of the need to link past events with dated events) would go a long way to resolve this issue (among many others). 

One difficulty in resolving pre- versus post- contact differences in the island’s landscape and ecology is the fact that point at which researchers arrived on the island to make systematic descriptions is more than 250 years after initial contact and decades after the island was turned into a sheep ranch. Certainly, the presence of 60,000 sheep and associated ranching activities likely resulted in the final termination of many plants that may have been present in small numbers in late prehistory.  So the timing of the final termination of the palm is still a bit unclear.

The second part of the question seems to assume that we (Hunt and Lipo) argued that it was “rats… cutting the trees down.” The statement is absurd to begin with and of course we have never argued this. What we have argued is that arrival of rats with humans on to the island brought immediate and substantial changes to the ecology of the island. The introduction of rats is really the introduction of the first teeth on the island and their presence (as is well documented in many environments) will impact native vegetation especially that which has coevolved dispersal mechanisms with birds. The impact of rat is a fact and indisputable given the evidence that exists of rat gnawing seeds. But did they “cause” the trees to go extinct (as this question implies we say)?

The answer is, of course, no. The rats did not cause the palm forest to go extinct for several reasons. First, things don’t “cause” other things to happen except in common sense (see Sellars 1963: Science, perception and reality).  Second, while rat predation on palm nuts has been an ignored factor in the vegetation changes that are commensurate with human arrivals, rats were not the sole factor.  We *do* know that rat predation on seeds can make massive changes in vegetation and even extinction even when humans are not present.  As Hunt has discussed, the elimination of Pritchardia palm in the Ewa Plain clearly predates the actual arrival of humans (see Hunt, T., 2007. Journal of Archaeological Science 34 (2007) 485-502; Athens, J.S., Tuggle, H.D., Ward, J.V., Welch, D.J., 2002. Avifaunal extinc- tions, vegetation change, and Polynesian impacts in prehistoric Hawai’i. Archaeology in Oceania 37, 57-78.p. 73).

On Easter Island with its tiny size (about 6x10miles), however, there was never a point at which rats were separate from humans. It takes about an afternoon to walk from one side of Rapa Nui to the other: human and rat impacts will be effectively simultaneous across the the entire island.  We know that the people arriving on Easter Island were slash-and-burn cultivationists — a strategy we side widespread across the Pacific (and indeed around the world). Their lives depended on transforming the environment to one that was capable of supporting human life through the growth of Polyensian domesticated plants. Thus, humans burned the forest down right from the get-go.  The combination of human burning for land clearance with rat predation on palm nuts would mean that the forest have a difficult time to grow back on its own.  Recent excavations by a Belgian team up at Vaitea (I believe: I heard about this second hand) show that in prehistory there were attempts to grow these palm trees. This is not at all surprising: the trees were certainly disappearing given activities of slash-and-burn and rat predation and this would be something that prehistoric people noticed (contra the assumptions inherent in claims by Diamond). 

What gets confused as a claim that we (Hunt and Lipo) argued that rats “caused” palm tree extinction are some comments that Hunt made in his paper in American Scientist that:

 

The evidence from elsewhere in the Pacific makes it hard to believe that rats would not have caused rapid and widespread environmental degradation. But there is still the question of how much of an effect rats had relative to the changes caused by humans, who cut down trees for a number of uses and practiced slash-and-burn agriculture. I believe that there is substantial evidence that it was rats, more so than humans, that led to deforestation.

and in his 2007 JAS article where he says:

 

In this review I have examined ar- chaeological, palaeo-environmental, and contemporary eco- logical evidence to suggest that the Pacific rat may have played a major role in Rapa Nui’s ecological catastrophe. The fact that rats alone are capable of widespread forest de- struction compels us to evaluate their contribution to the trans- formation of Rapa Nui, as well as in other island ecosystems. While I argue that the role of rats has often been underesti- mated, direct human actions of felling and use of fire likely have played a significant role as well. Additional research will be essential to disentangle the contributing factors. The environmental catastrophe of Rapa Nui is likely a complex history, one that has been masked by speculations about the in- tentions of people cutting down the last tree. Indeed, the ‘‘last tree’’ may simply have died. Rats may have simply eaten the last seeds. Perhaps the lessons of Rapa Nui tell of the effects of invasive species, invasional meltdowns, and the synergy of ef- fects that ensue as people and their portmanteau biota reach evolutionary isolates in the remote islands of the Pacific. 

But what is clear in the context of these quotes is that what Hunt is arguing (as we both do later on) is that the loss of the forest is the outcome of a number of factors among which rats is one. It is certainly possible to argue that rats could have caused the extinction of the palm trees, but in the case of Rapa Nui it also seems clears that the rat predation was occurring simultaneously with human burning and clearing of the palm forest. Empirically, this is undebatable  as we have rat gnawed seeds that are found contemporaneously with burned palm. 

It is also silly to argue that the presence of non-gnawed seeds somehow “disproves” the role of rat predation. Some nuts probably didn’t get eaten especially if the tree was burned before the rats were able to consume them.  Even a small impact to seed production for these trees is likely to have caused changes in the life history structure of the forest whereby there become fewer and fewer young trees. Rats do not have to eat every single palm nut for the forest to go into major decline or even extinction. Clearly the r-selected strategy of palm trees embodied by nut production is a testament to the fact that the palm is evolutionarily successful by maximizing the number of offspring due to the fact on average some of the nuts will grow into new trees, not all.  The novel introduction of toothed predators likely only had to have a small effect to have upset the balance between forest regeneration and failure. Of course, this is topic that clearly needs more research. 

Question #2:  Canoes and Dolphins: In the second part of his/her question, A Sophist writes: "2. If Palm Trees are unable to be made into canoes, how did the people make ocean going canoes?”  I guess the assumption here is that the presence of dolphin remains at Anakena must somehow have required large ocean going canoes. It also refers to the fact that we argue that palm trees are not useful for constructing canoes, at least not the sailing/voyaging canoes used by Polynesians. To disentangle this question, let’s start by saying that it is likely that whatever canoes brought people to Easter Island were likely around for some period after their arrival. We don’t know this specifically since we have no evidence but the faunal record seems to record more deep water/pelagic fish in the early assemblages than later. The acquisition of these fish would have required canoes and early on there would have been the original canoes to use.  It also seems that at some point these canoes rot away, are lost, or used to sail elsewhere as the faunal remains show significantly less pelagic fish. From that point on the emphasis of the population was nearly entirely on terrestrial resources (though some small % of fish from the limited nearshore reef seemed to supplement the diet). The palm trees appear to have been lost over 4 centuries were not used in canoe manufacturing even though they were present.  This is almost certainly because palm trees are not good raw material for canoes: they are flexible grasses filled with mush. 

The presence of dolphin remains at Anakena is certainly interesting but it doesnt seems to contradict our overall understanding of the archaeological record.  The remains are few in number and were never a major source of food. Ethnographically we know that dolphin come into the Anakena bay and were sometime hunted there. The bay is shallow. Traditional means of hunting dolphin often involved trapping them in shallow water by driving them toward shore with rocks knocked underwater (see http://www.youtube.com/watch?v=QP3FbrF5YyM if you stomach it). Deep water canoes were not necessary for hunting dolphin. 

Final Comment:  The final comment by A Sophist is a bit puzzling: "This seems to be a lesson in how isolated political leaders who do not feel the pain of their actions (cutting down the forest for whatever bloody reason: fuel, canoes, to move statues, etc) can lead their society to the brink of destruction. “ It is not clear at all what “this” refers to or who the “isolated political leaders” are or what “brink of destruction” means. Inherent in here is the idea that somehow the forest was a vital resource upon which people depended. The fact is that there is no evidence that palm trees ever played a central role in the subsistence or settlement activity of people of the island. As sweet potato farmers, the clearance of trees (like all farmers) resulted in more land available for growing crops. The burning of the forest resulted in temporarily increased nutrients in the soil. The fact that rat predation (not to mention the slow growth and reproduction of the tree itself) meant that the forest never regrew was not a catastrophe. Alternative (laborious yet, but indeed clever) means of enriching the soil through rock mulch as well as intensely tended gardens (manavai) were able to keep the soils growing food. The trees simply were not a vital resource to the prehistoric population.

Monday, October 28, 2013

NIR Raspberry Pi Camera

I am excited to read that one can now buy a near-infrared Raspberry Pi camera. The regular one  can be modified to measure NIR light but the process is futzy and error prone. I destroyed 2 cameras trying to get the damn thing apart. This new camera has the NIR filter removed so one is set to go right from the start.  Adafruit has them in stock (as of this morning but I’m fairly certain they will sell out quickly). 

http://www.adafruit.com/products/1567

My efforts to build the RPi multispectral camera are now made much simpler: http://www.evobeach.com/2013/09/a-raspberry-pi-based-multispectral.html 

Friday, October 18, 2013

Remote Sensing with UAVs and eCognition

PLoS published an interesting new article about the use of UAVs to track invasive weeds in maize fields using UAV imagery and remote sensing techniques. This is a good example of an article that uses remote sensing and UAVs in an analytic sense and not just "camera in the air." While elevated camera angles are cool, they do not really take advantage of the technology nor offer much in the way of actual research. This article points to how this kind of work can be done (and will be a good article to use for our REU program). http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0077151