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CSULB Geospatial Research and Mapping (GRAM) Field Program
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Daily Blog for Cole Anwyl Walters


An End to an Adventure

Posted on July 3, 2013 by Cole Anwyl Walters

I’ve had a couple of days to reflect and think about this post.

I finally presented my final presentation. It went really well and seemed like everyone was fairly interested and impressed of what I had come up with the past couple weeks. The archaeology students also seemed intrigued.

Then it was time to start packing up and saying goodbye. I realized how powerful of an experience this had become. The people I had met and the things I had done were incredible. The thought of graduate school in the coming year not only intrigued me, it excited me. I had practiced what I had loved and done it with intelligent, thoughtful people.

I want to thank everyone for their help this year. Everyone will be missed and I will think of everyone often on their journey to success. Please stay in touch and I will try to do the same.

 

Now i’m off to another adventure! To China!

Writing Day and My Last Visit to the Field

Posted on June 27, 2013 by Cole Anwyl Walters

This morning I got a ride with Emily to the field to formally take pictures of what I think are the most interesting areas for my presentation. In addition, I personally said goodbye to the Kaa’a'wa Valley.

The rest of the day I wrote and finished the writing section of the presentation. This is the first time I’ve had to explain some personal research that I’ve grown attached to and its hard developing it in an unbiased manner. Tomorrow I will do the PowerPoint section and prepare for the presentation on Friday

 

Cole Anwyl Walters

Biomass Calculation Complete

Posted on June 27, 2013 by Cole Anwyl Walters

Today I did the final calculation for the supposed biomass of the hectare plot. While it was enjoyable for a short moment, I concluded that the amount was much too high. this was expected due to the belief that the volume blocks are thrown off from the Monkey Pod Trees. In addition, I have no way of calculating the unoccupied space under the canopy. These are turning out to be my largest means of error and will probably play a great deal of road on my presentation Friday. I started writing due to my frustration of the whole project. I finished the introduction and plan on developing my methodology section tomorrow.

Just keep swimmin’

 

Cole Anwyl Walters

A Monday…

Posted on June 27, 2013 by Cole Anwyl Walters

Stayed in the Barn today and I’m afraid I will be doing so the rest of the trip. Today I finished processing the data and was able to get my final volume. Tomorrow, I will insert the suggested volume amount into the biomass equation from the Brown study to see how close I might be.

Today just seemed long aster a enjoyable birthday weekend.

 

Cole Walters

A Day Off!

Posted on June 24, 2013 by Cole Anwyl Walters

Paul and Thomas woke me up at 5:15am this morning so we would go snorkeling on the other side of the island. We ended up in a nature reserve  near Honolulu. We spent a couple hours snorkeling, watching all the tourists, napping in the beach and getting rid of our farmer’s tans. In the end, we didn’t even have to pay for admission or parking because we arrived so early.

Next we stopped for an early lunch at a hamburger place. It was nice to get some fast food back in my system. Afterwards, it went to Jamba juice to grab something to drink.

We stopped at Pearl Harbor after that. I had not been here since I was a kid so it was a much different experience, actually understanding what had gone on there. However, we were unable to get tickets to visit the Arizona memorial so after seeing the museum on the land, I spent some time at a bench thinking about my project and what the next steps were.

What I concluded:

Finish processing the imagery

Eliminate unwanted imagery

Measure the Photoscan to  one hectare

Further process and take the volume

Calculate the volume to biomass

 

In the afternoon, we went to Waikiki beach, relaxed in the sun and shopped at the international market. I bought myself a new hat and grabbed dinner at a decent sushi place. Overall, it was a successful day off on Oahu!

 

Cole Anwyl Walters

 

 

 

My Birthday!

Posted on June 24, 2013 by Cole Anwyl Walters

Happy Birthday to myself! My Pentax arrived yesterday and now its time to go use it for the first time! Paul and I met up in the field and got the camera strapped in a quad-copter for interval shots. I spent most of the time flying the quad copter rover the remaining canopy, going back in forth so I had even coverage over the northern side of the plot. Compared to previous experiences, it was much harder to fly the copter over this area because of the prevailing winds and fifteen minute showers.

When I got home, I immediately exported the images from the new Pentax and started processing the photoscan. The images pretty much came out perfectly and I couldn’t be happier with the results. I did a few other things with the photoscan to prepare it for further calculations and took the rest of the afternoon off to celebrate my birthday off.

Emily bought be a big cake to share with anyone and it was delicious! Thanks Emily!

The rest of the night we relaxed and went night swimming before getting ready for a day off in Honolulu!

More Points and Not Enough Imagery

Posted on June 24, 2013 by Cole Anwyl Walters

Today we visited the field again and my original goal was to collect more imagery that I was missing (particularly in the north side of my patch of land). I looked for a Pentax to fly with but I wasn’t able to get my hands on one so I decided to help Howard with his Imagery on the South Side of the valley. While the winds picked up and the rain came, I knew he would need someone else to pilot the quad copter.

After flying the quad-copter for awhile, I decided to head back to base camp to grab a Yuma and collect some georeference points. this poised to be fairly difficult as the Yuma didn’t work perfectly. Three georeference points were collected in total so I could later calculate the volume of my Photoscanned plot.

While I wasn’t able to get my hands on a Pentax, my personal one I had ordered arrived in the mail. I prepared it for taking imagery tomorrow and I spent the night getting my research organized and ready for the final steps.

 

Cole Anwyl Walters

A Day In to do Research

Posted on June 21, 2013 by Cole Anwyl Walters

In the morning, we took a trip to the field so I could some more image son my canopy. Within the first hour I was there, I couldn’t get my hands on a Pentax. Briton was taking a trip home so I decided to take advantage of it by hashing out some hard research and it turned out to be pretty productive. I wrote up a formal report of my option so I could keep my thoughts straight.

There are several ways that I can determine slope and the y-intercept when determining the relationship between biomass and NDVI. The simplest and crudest is by eye. You wouldn’t do it this way to publish the work, but estimates by eye tend to be very close to the real values. However, this statement is only true if someone is fairly practiced at measuring biomass and working with it in the field. Considering that end of that circumstance, measuring biomass from “the eye” is off the table. A more robust way is to use methods called least squares, or maximum likelihood, which end up being the same in this case. You can do this using any statistical software.  Note that developing this kind of statistical model assumes that there is a linear relationship between the two variables. This might not be true. For NDVI, I would not be surprised if it saturates, so that biomass increases with NDVI, but then levels off. Not only is this saturated response common in many wet environments, it is particularly notorious for being a false method of biomass analysis in tropical environments. Basically, when vegetation is extremely thick, the usefulness of NDVI becomes void in the sense of measuring biomass.

Many of the studies using regular imagery seem to be annual long studies, taking seasonal data on soil, stand and AGB measurements on micro plots.

 

Option 2: Leaf Area Index (LAI)

 

LAI is generally defined as one half of the total leaf surface area divided by the ground area. Tremendous effort has been invested in developing algorithms to extract LAI from remotely sensed data, as this is perhaps the only viable option to estimate LAI in detail over a large area. There are numerous other factors influencing the spectral signals at the top of canopy in addition to LAI (leaf angle distribution, leaf clumping, sun and viewing angles, background conditions, etc.)

Leaf Area Index as an option is pretty much in the same “boat” as NDVI when considering its usefulness on our time scale. Many uses of LAI to consider biomass are not done in tropical environments and are usually done the course of growing seasons.

 

Option 3: Lidar in a dense canopy

Initial analysis showed that the canopy from which I’m looking it was on partially penetrated from the coastal Lidar collection. This is not particularly unusual considering how dense the canopy is near the staging area. The only useful form of Lidar when measuring canopy density and biomass in a tropical rainforest is wave form due to its ability intercept surfaces from top to bottom of the canopy area under study. This form of Lidar has been adopted by NASA and called LVIS….

 

“LVIS measures the roundtrip time for pulses of near-infrared laser energy to travel to the surface and back. The incident energy pulse interacts with canopy (e.g. leaves and branches) and ground features and is reflected back to a telescope on the instrument. Unlike most other laser altimeters, LVIS digitizes the entire time-varying amplitude of  the backscattered energy (in 30-cm vertical bins). This yields a ‘waveform’ or profile related to the vertical distribution of intercepted surfaces from the top of the canopy to the ground (see Fig. 2 and Blair et al., 1999;

Dubayah & Drake, 2000; Dubayah et al., 2000).”

Because of this systems ability to go through tropical rain-forest density, it has been adopted in research projects across South America where dense vegetation occurs.

What this means…

 

The format of my paper is going to have to change, From this analysis, I won’t really know the true biomass of the plot, but will still show that Photoscan has the ability to maybe one day calculate biomass in a nondestructive manner.

 

 

Cole Anwyl Walters

Day 17: First to Fly

Posted on June 20, 2013 by Cole Anwyl Walters

Today was my first day on data collection considering my individual project. After arriving at the site, I took one good lab around to observe my hectare wide spot to get a good idea of what I was up against. I carried the Yuma around with me to take five strategic points that I think easily define the boundaries of my hectare. I also scouted for georeference points that I think will come out easily in my Photoscan.

After this step, I conversed with Paul to find out the best way to fly my plot. This wasn’t a no “brainer” surprisingly. I need to decide how detailed I wanted my my plot of land to be. The higher I flew, the less data I would need to process and smaller more manageable model would render. The lower I flew, the more possibility that a 3D model wouldn’t render, but I would have a larger model to calculate volume from.

I decided to fly in both heights to see what the results formed. I took five flights up using a Pentax.

When I came home, I processed the data and stuck it into Photoscan. The 3D model rendered usable. However, I think measuring volume may be more of a challenge than anticipated.

Tomorrow, I will fly more, try to make headway on getting an NDVI of the area and try to use ground based images in Photoscan.

 

Cole Anwyl Walters

An Extremely Productive Day-Probably My Best Post

Posted on June 19, 2013 by Cole Anwyl Walters

While not visiting the field today, the team met up at 8 am this morning to hash out research topic ideas and offer alternative ideas and critical construction. I presented my idea of calculating Biomass from Photoscan on a micro site level and everyone seemed to like it. After some discussion and thought, it seemed the best area for study was the Hao and Monkey Pod Trees located directly at the staging area (shouldn’t get lonely working on my project). However, discussion arose between Dr. Lee and I when considering how to calculate Biomass in a traditional manner without a preexisting  models. I did some infant stage research on this topic and thought about about it pretty much the whole day. This is what I came up with….

To calculate biomass from remote sensing, I will need some estimate of biomass from the field, and remotely sensed data from the same locations. I then plot one against the other and measure the statistical relationship between them. By convention, the thing you want to predict should be on the Y axis, and is called the dependent variable. The X axis would be the remotely sensed data – NDVI in my case. The kind of analysis I will need is called a linear regression, and it amounts to finding the line that goes through the data and predicts Y given X. This is just the familiar Y = mX + b.  Once I know m and b, I can predict Y at locations where it has not been measured but I know X.
 —–Obviously this is fairly simplistic and basic, but it plays an important role in developing a theoretical model for my project.
I contacted a professor of mine who works on calculating biomass with Dr. David Clark and he pointed me to some literature which might lay out a useful plan for my research project. He suggested that the paradigm for calculating Biomass is in need of change and that real hard, ground “truthing” is needed to “accurately” estimate the biomass of a given area unit.
After a discussion with Paul and Dr. Wechsler in the later afternoon, Lidar imagery does exist to the point of my study area, In my opinion, this completely changes the game and I will need tomorrow to know exactly how useful the Lidar imagery will be for me and the project in the coming week.
Cole Anwyl Walters
University of Maryland, College Park

About Cole Anwyl Walters