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Mar 21 2012

Herbert Run Update

On Monday (3/21/2012), Andrew and I went to Herbert Run to survey more points to make a grid so that we can start mapping trees.  By the end of the day, we finished enough points to have ten 25 by 25 grid points marked and ready for tree mapping.  We begin mapping trees today (3/21/2012).

Mar 20 2012

New Jersey Pinelands Fire Research Flight

This past Tuesday (3/6/12) Jonathan and I travelled to New Jersey to conduct wildfire research.

We left Monday evening and drove to the New Jersey Pinelands, where we stayed overnight at the research center.  Our first obstacle was the smoke research payload.  When Jonathan did this smoke research in the past, he had suspended the payload (consisting chiefly of a smoke detector and data logger) on a tether beneath the hexakopter.  The reasoning behind this was that we needed to keep the payload well away from the air disturbance made by the hexa's propellers.  However, the problem with this method is that the hexakopter is unable to self stabilize under a suspended payload, and ends up swinging the payload wildly and eventually crashing.

Jonathan and I did a brief test to confirm that this behavior was still present with the fire payload, it was.  As a solution, we mounted the payload on top of the hexakopter's dome.  A strip of ribbon attached to the top of the payload served to demonstrate that the propellers did not significantly interfere with the airflow though the payload when it was mounted on top.  The hexakopter was perfectly stable with the top mounted payload. 

Tuesday during the wildfire we flew from the research compound which was downwind of the wildfire in the smoke plume.  The hexakopter flew up in 50 meter increments and back down every half hour or so for several hours.  Overall our data collection was a success.  Towards the end we even had the time to mount a camera on top of the payload to take a rather jittery video of the wildfire from the air.

Mar 16 2012

Updates: Hexakopters, Quad Arducopter and Octocopter.

Now that the hexakopters are basically complete (one has a programming error that we are currently working on), Stephen and I decided to work with our other projects: quad arducopter and octocopter.

The quad arducopter (4 blades) is working.  We spent a few days familiarizing ourselves with the parts of the copter using the arducopter wiki (http://code.google.com/p/arducopter/wiki/ArduCopter).  The electronic speed controller (ECS) still needs to be calibrated, but it the copter is connecting to the computer and seems to be in working order.  We have started the parts list so that we can move forward.

The octocopter (8 blades) is still in the supply obtaining phase.  We have already placed our order for the necessary parts to construct the copter.  Within a few weeks we shall have those supplies and can commence the construction!  The objective of the octocopter is to run the trials the hexakopters are currently doing, but more efficiently.  It is also hoped that we can use the octocopters to expand the scanning area. 

Mar 07 2012

Finishing the survey grid

There have been many issues that have presented themselves while trying to survey this particular section of woods. There are many drastic elevation changes and two of our points appear to lie in the middle of the only small stream found in this section of forest. The surveying must be completed before the trees start to bud otherwise visibility would be virtually impossible to obtain, this being chief issue with the completion of the survey grid. When there is an accurate survey point set we can only plot a half a dozen points before needing a new point to shoot from due to visibility issues. Initially we discovered a way to make a new reference point through resection however Andrew and I soon discovered this was not an accurate enough approach to finishing the grid. A few more reference points must be measured before the grid can be completed and tree marking begins. An accurate effective method of tree marking must be used and we are in the process of obtaining Dr. Richard Condit's Tropical Forest Census Plots: Methods and Results from Barro Colorado Island, Panama and a Comparison with Other Plots. Hopefully this will give us a new outlook on how to plot the trees in the most precise manner.

Mar 05 2012

Welcome New Ecosynth Users!

Just a quick post welcoming Jessica Breen and Steve Klosterman as new members of the Ecosynth blog.

Jessica will be pursuing a Ph.D. with Dr. Ellis in the UMBC GES Department this coming fall.  She has had experience with kite aerial photography and is interested in citizen science remote sensing.  She keeps up a blog about her experiences, An Accidental Geographer.

Steve is pursuing a Ph.D. at Harvard University with Dr. Andew Richarson.  He is interested in deploying multirotors for personal remote sensing of forest canopy phenology.

Welcome Jessica and Steve!

Mar 04 2012

Traversing vs. resection

  After careful research I realized my understanding of resectioning was not clear. Resectioning a control point is not the most efficient way to establish new control in alot of ways its a waste of time. A better way of survey control setting would be traversing.

With resection I noticed that you can use 3 known points to determine a unknown point.The problem with this is, I would need to be set up some where roughly in the middle of the three points because according to the owners manuel for the total station, the further I am from the center of the points the less accuracy I will have in creating my new control points. I observed this to be true because no matter how many new points I created they were all off by and angle of at least 1'.

This led me to consider another method of creating control; traversing(picture shown below). Traversing is the method that all modern surveying is done with. This method allows me to broaden my survey network while also creating new control points. Triangualation deals with an X,Y cooridinate system and the pythagorean theorum in order to determine the exact differences between many points. Traversing uses a R,Theta coordinate system of vectors to determine the relative distances between many points. Where you would use a magnitude R and a direction determined by some angle "Theta". What you see below is a "closed traverse". This is the most widely used surveying method today because it is quick and efficient. basically what you do is you begin and end on the same point calling them different points. You have at least three traverse in a loop. What you do is collect many measurements of the distances and angles inbetween three points. By setting up on one point and backsighting and forsighting two other points. After this it will propogate the error and evenly distrubute it throughout the three points. This process is repeated howevermany times until you have a sufficient amount of control points to cover all your mapping and stake-out needs. When your loop reaches the first point agian, you would simply give that point the next highest number and throw a control point there. Then after this you would do a closure check which has two components. First I would check the relative distances between the two points. For example, in the figure below if I were to call the point that the total station is one traverse 106 and where the forsight is the next point counter clockwise ( you always throw traverse counter clockwise, this is shown but not said in the figure) traverse 107/101 then I could collect the sets and check realively speeking how close 107 is to 101. The ideal situation is that they have the same coordinates exactly which is never the case. After the closure process. You can use the data collectore to basically distribute all the error in this ring throughout the ring and make a super accurate set of control points. Finally I would use the equation (n-2)180 and if the angle is withing (+-) some relatively small angle difference, then the traverse loop has good closure. For example on this one below we have six angles

(6-2)180degrees=720degrees 

Therefore if the angle was 720degrees00'05" then I would definitely keep it because this traverse has good closure.

In order to do this I will need a data collector. Here is an advertisement that shows the whole process of traversing and also could be a good data collector to buy

Traversing by Repetition With the RECON Data Collector - YouTube

I think we need to get a data collector as well as the other equiptment that I have put on the Surveying equipment order.

 

Feb 29 2012

Resection

I found that I might be able to create my own control points if I use the resection function of the total station. Basically what the instrument does is it takes multiple measurements  between two points from a central travers set up. Then what it does is it takes the standard deviation of all those points. From there if there was a measurement that has a particuarly high sigma you can throw it out. this technique will make throwing my own control points easier hopefully since I am already have a useful set of reference control points.  The problem I was having with setting up my own control points before was that I had nothing to go off of except assumed coordinates which have to eventually be rotated onto UTM coordinates in order to actually have  been able to do any of the stake out that we have so far.

Feb 29 2012

64-bit Python Computing

Recently I ran into a memory problem running large point cloud arrays through Python and Numpy.  I quickly determined that I was asking Numpy to work on massive arrays that were exceeding the limits of the 32-bit Python process in Windows.  I came up with a workaround whereby I truncate the UTM X-Y coordinate information so I can store the numbers as 32-bit floating point values without losing precision, then add the extra numbers back at the end.  Basically, I translated the X-Y coordinates (352845.49 4346713.91 --> 2845.49 6713.91) then back again to the original UTM values after computation.  This was OK, but I wanted to overcome the 32-bit limit in Python.

There are unofficial 64-bit builds available here, but I wanted to try something established.  I got one of our machines running dual-boot Windows 7 / Ubuntu 11.10 64-bit and compiled all the Python, Scipy, and Numpy libs in Ubuntu.  These builds are inherently 64-bit because of the 64-bit OS install, so there are no issues with addressing large arrays of data.  Back to work!

Feb 27 2012

SERC Leaf-off Hexakopter Mission

This past Sunday (2/26/2012) Jonathan, Shelby, and I went to the Smithsonian Environmental Research Center to fly a hexakopter mission during leaf-off.  The image on the left was taken by the camera mounted to "Sally" as it was coming in for a landing.

Since "Raven" still has what we believe is a motor controller issue (contacting Nisarg about this), we brought "Roflkopter and "Sally" to SERC.  Initially "Roflkopter" was designated the primary flight hexakopter, because "Sally" had been noticed as having stripped threads on one of the propeller mounts on top of a motor.  Since the other two holes in the propeller mount were not stripped, we still considered "Sally" flightworthy, just not primary.

Once on site, Shelby and I set up a series of twelve orange contractor buckets along the road through the forest we were surveying.  Jonathan had programmed the rough distribution of them into the dog-tracker GPS to follow when we were setting them out.  Then throughout the rest of the day during flights and other work, we used a handheld GPS tool to determine the precise coordinates of each bucket.  These coordinates will be applied to the buckets in the point cloud representation.

As it turned out, "Roflkopter" was not our best choice for primary hexakopter.  Although it was certainly flightworthy, during flight it bobbed up and down instead of flying in a straight line.  Jonathan believes it is due to the hexakopter's vertical lock setting being miscalibrated or otherwise dysfunctional. 

We decided to fly "Sally" to see if we could collect data from a smooth flight.  After some test flights, we determined that the stripped screw on "Sally's" propeller mount was not going to be an issue this mission, although it will still be replaced.  On "Sally's" first mission, everything seemed to go well but when it returned the camera had run out of battery.  This was odd since the battery we used was most definitely fresh.  The camera did not seem to respond well to new batteries either, so we flagged it for later investigation and switched to a new camera.  Finally, "Sally" flew a successful flight and collected what looks like it will be a complete set of pictures of the forest canopy.

Feb 20 2012

Week of 2/13/2012: Flying the hexakoptors and surveying in Herbert Run

This week Stephen and I finally got to fly the hexakoptors.  It did not take long for us to realize that it is rather difficult to learn to fly them.  We will be practicing on flight simulators before we take the hexakoptors out again.

During the weekend, Andrew and I went to Herbert Run and surveyed the area to make a grid.  We accomplished to get a fourth of all of the points done!  Hopefully we can be as progressive in weeks to come.

Picture 1: Hexakoptor in flight.

 

Picture 2: Me after a day of surveying.