Construction of Balloon Mapping Equipment

Construction of a helium balloon and camera rig to do small scale remote sensing.

Introduction:

This week we spent preparing for two future projects. Much of the time involved research and development of weights and measures, camera rigs, parachute testing and testing of a tracking beacon. One of the projects involves small scale aerial mapping using a digital camera rigged beneath a helium filled balloon floating at about 500 feet above the ground. The balloon will be tethered to a person on the ground guiding it around the area of interest. This may be a good way to obtain high resolution images of a small area at a very reasonable cost. Many remote sensed images available are 2 meter by 2 meter resolution; depending on the camera used and the height obtained by the rig, our images could be down to centimeters of resolution. The second project nicknamed HABL (high altitude balloon launch), includes building another camera rig, again to be fastened beneath a helium filled balloon. This rig will be allowed to fly as high as it is able, it will not be tethered to the ground. As it rises it will record video of its journey. After HABL reaches its maximum altitude, it will deploy a parachute to slow its descent. This rig will be fitted with a tracking beacon for retrieval. We worked in several groups on different aspects of the projects: HABL, parachute testing, weights, camera housings and a tracking beacon. My groups work follows.

Methods:

The first objective was to test several digital cameras to see if they could shoot pictures in a continuous mode and identify the process to get the camera into that mode. The camera I studied was a Panasonic Lumix DMC-F28. The process involves several  steps as follows: 1, remove the lens cover; 2, turn the camera on; 3, press and hold the multi-frame/garbage button for about 1 second; 4, use the arrow keypad to select unlimited; 5, press the set/menu button to confirm the selection. After which the camera is ready to use.

The second objective was to modify the camera to be able to shoot in continuous mode without having a person to hold down the shutter button. We accomplished this by wrapping a heavy rubber band around the camera over the shutter button and placed a small piece of cable tie on the shutter button under the rubber band; a small piece of paper folded up, a pencil eraser or any other small object that that will hold down the shutter button as well. This allows the camera to function while floating hundreds of feet in the air.

Fig. 1. We wrapped a rubber band around the camera, over the
shutter button and placed a piece of a cable tie under the band to keep the
button pressed. Now the camera will be able to take continuous images
 while suspended from the balloon.

The third objective was to build the rig that supports the camera beneath the balloon. We had two groups working on two different designs. One group followed instructions obtained from an online source (http://archive.publiclaboratory.org/download/Grassroots_Mapping_English_2_0.pdf) which describes a rig that works using the top half of a soda bottle; however, after some research my partner and I were not happy with how the rig seemed to spin a lot, as evidenced by the directionality of the online photos. We decided to attempt to build a more aerodynamic rig to reduce the amount of movement in the camera and rig by turning the bottle on its side.

Tools and equipment used to build the rig included scissors, scalpel, cordage, 2-2 liter soda bottles, a large rubberband, a sharpie marker, metric rulers and 6-10 plastic cable ties (figure 2). We began by measuring the height of the camera, most of the cameras we measured were about 6 centimeters (cm) tall and the width of the lens, ours was about 4cm, we will need this later. Next, we took the large rubberband and stretched it around one of the soda bottles, end to end, across the cap and around the bottom (figure 3). We checked to see that the bottle was bisected into two equal halves lengthwise. We then used the marker to mark the bottle down both sides using the rubberband as a guide (figure 4) after which we removed the rubberband. Next, we measured up from the bottom of the bottle on one of the lines and marked out 5 and 20 cm. At both of these points we measured around the bottle, out from the line, in both directions 5 cm then connected the four points giving us a 10cm by 15cm square. Using the scalpel (figure 6) we removed this section of the bottle, this will be where we insert the camera and our viewport (figure 7).

Fig. 2. These are the tools and equipment needed; 2 2 liter soda
bottles, 2 rubber bands (one short heavy, one long), sharpie
marker, cable ties, twine, a scalpel and a pair of scissors(not pictured). 

Fig. 3. Use the long rubber band to bisect the bottle
into two equal halves lengthwise.

Fig. 4. use the sharpie to mark the center line of
the bottle, on both sides, following the rubber band.

Fig. 5. On one side of the bottle, measure from the bottom and
mark at 5 cm and at 20 cm. Then extend these lines around the
sides of the bottle 5 cm in either direction. 

Fig. 6. Connect the corners of the 10 cm by 15 cm rectangle and
use the blade to carefully cut on the lines.

Fig. 7. Remove the panel, now we have access to the inside of the
bottle and we have our view port. 

Then we moved to the other side of the bottle. Here we measure up from the bottom of the bottle on the other line and mark at 4 cm, 6 cm, 12.5 cm and 20 cm (figure 8). At the 4 cm mark we measured out in both directions from the center line and made a mark at 1.5 cm (figure 9). These two points should be 3 cm apart and 4 cm from the bottom of the bottle. At these two points we made vertical (the same direction as the length of the bottle) ¼ inch incisions in the bottle (figure 10). The same procedure was used at the 6 cm mark.  These holes will be used to fasten the wing and the suspension string to the body. Then we measured and marked both up and down the center line from the 12.5 cm mark, half the distance of the width of the camera lens 2 cm (4 cm total) (figure 11). This part may vary depending on the camera, but the lens at 12.5 cm with the camera weight forward balances fairly well, not precise.  At these points we measured out from the center line in both directions 3 cm (figure 12). We now had four points that measured 4 cm by 6 cm; we made ¼ inch vertical incisions at all four points. These will be used to mount the camera inside the housing. At the 20 cm center line mark we again measure out away from the center line 1.5 cm and made ¼ inch vertical incisions (figure 13). These will support the forward suspension cord.

Fig. 8. We measured from the bottom on the opposite
side of the bottle using the center line as a guide and
marked at 4 cm, 6 cm, 12.5 cm and 20 cm.

Fig. 9. At the 4 cm and 6 cm marks we measured out in
both directions from the center line and made a marks at
1.5 cm. These four points should be 3 cm apart and 4 cm
and 6 cm from the bottom of the bottle.

Fig. 10. At the  points we made vertical (the same direction
as the length of the bottle) ¼ inch incisions in the bottle.

Fig. 11. We measured and marked 2 cm from the 12.5 cm
 mark, the total of 4 cm is equal to the width of the camera lens.

Fig. 12. We measured out from the center line out in both
directions 3 cm. At the four corner marks we made ¼ inch vertical incisions.

Fig. 13. At the 20 cm center line mark we measured out from
the center line 1.5 cm and made ¼ inch vertical incisions.

To aid with stabilization in the moving air we designed a wing. For the wing we cut a 10 cm by 20 cm section from a second soda bottle (figure 14). The piece was removed near the center of the bottle to reduce distortion due to curvature of the bottle. The 10 cm dimension is along the long axis of the bottle and the 20 cm dimension runs around the bottle. We measured the wing and marked it at 10 cm drawing a line that divided it into two equal halves. We measured on the line from one side and marked it, drawing a line at at 2 cm (figure 15). We used these two points to line the wing up over the 4 cm and 6 cm marks on the bottle, the long side of the wing should hang off the back of the rig. We lined up the points with the concave side of the wing against the bottle (figure 16).  After the points were aligned we marked the ¼ inch incisions on the wing, now we could make corresponding incisions in the wing.

Fig. 14. We cut a 10 cm by 20 cm section from a second soda bottle.

Fig. 15. We measured the wing and marked it at 10 cm drawing
a line that divided it into two equal halves ( horizontal line).
 Then we measured in from the edge on one side and marked it
drawing a line at 2 cm .

Fig. 16. We used the lines on the wing to reference
it against the four slits in the bottom end of the housing.
Now we were able to make incisions in the wing that
corresponded to the housing.

We used 90 cm of cordage to suspend the rig. I tied an overhand knot (figure 17) in each end of the cord (figure 18), this is a good knot that will not slip and it provides a loop to secure the rig to.

Fig. 17. I folded about 8 cm of the end of the
cord back on itself then  made a simple overhand knot.

Fig. 18. We tied knots in both ends of the cord to
secure it to each end of the rig.

To assemble the rig we ran two cable ties from the inside of the bottle out the left side 4 cm and 6 cm incisions. The wing should now line up convex side against the bottle and the long side of the wing should be to the back of the rig. We ran the cable ties up through the corresponding holes in the left side of the wing (figure 19) and the tie at 6 cm through one end of the suspension cord (figure 20), and then we ran both ties back through the holes in the right side of the wing and into the bottle. After we had both ends back inside we were able to zip them together tightly and cut the excess off (figure 21).  At the center four incisions we ran a cable tie into each of the left side slots from the outside to the inside then back out the right side incisions (figure 22). At the 20 cm incisions we again ran a cable tie from the inside of the bottle out through the left side incision and through the other end of the suspension cord and back into the bottle through the right side incision (figure 23). We pulled the cable tight and removed the excess.After the camera was set to take photos it was placed into these ties with the lens towards the back of the rig, the ties were tightened and we were ready. There was need for some minor adjustment to ensure the rig was level reducing any roll or pitch that may occur during operation.

Fig. 19. We ran cable ties from the inside of the housing out
through  two of the back holes of the housing. 

Fig. 20. The foremost of the two back ties was also fed through
one end loop of the suspension cord.

Fig. 21. Both ties were securely tightened and the excess was
removed with a scissors.

Fig. 22. We inserted two cable ties into the left side of the
housings center holes and then they were then fed back
 out but not fastened, these will support the camera.\

Fig. 23. Similar to the back holes, we fed a tie out from inside
the housing and through the other end of the suspension cord.
The tie was fed back into the housing and secured.

Discussion:

Our rig may work well or it may fail completely, testing it with some air such as a fan might be a good idea. If it fails it would be better it fail in our hands than a fall of several hundred feet. During construction Martin thought we may have trouble because the internet plans suggest the lens of the camera be about 2cm from the bottom of the housing, ours is much deeper. I believe this has to do with the field of view of the camera. After testing our rig it performs well with no interference from the housing evident within the photos. Another of the differences that I believe allow our rig to be successful are our camera is secured directly to the housing which minimizes movement; the other rig has the camera suspended from cordage inside the housing. Weight is of importance during these tests (figure 24), we need to know how much each part weighs also the whole rig including the balloon so we get the correct amount of helium in the balloon to achieve lift. Our rig weighed about 239.69 grams when weighed with the Cannon camera. After completion of our rig we have affectionately named it the Hindenburg. 

 

Balloon Mapping Weight Chart
Item	Weight
Balloon (Orange)	315.5 g
Balloon (Red)	322.25 g
Black rubber ring (~1 inch)	8.25 g
Camera (Biggest, black)	392.17 g
Carabineer (blue with key ring)	4.79 g
Carabineer (silver with loop)	26.71 g
Coke Bottle (2 liters, empty, whole with cap)	50.86 g
Coke Bottle (Top, Label "1")	18.6 g
Coke Bottle (Top, Label "2")	12.5 g
Handwarmers (2 in package)	54.37 g
Jif Peanut Butter (No cap, empty, whole)	48.6 g
Memory card (16 gb)	2.16 g
Memory card (32 gb)	2 g
Minno Thermo with lid and rope	75.85 g
Mt. Dew (2 liters, empty, whole with cap)	52.08 g
Orange Camera (No memory card)	185.77 g
Parachute (blue and orange)	144.7 g
Pink Rope (1 meter)	1.15 g
Rainex Bottle (Empty, whole with cap)	141.36 g
Rope (150 ft.)	416.51 g
Rubber band (black, midrange)	2.8 g
Rubber band (blue, thin, medium)	2.37 g
Rubber band (Extra small, orange)	1.14 g
Rubber band (long, tan, thin)	4.7 g
Rubber band (long, white, wide)	14.4 g
Rubber band (short, white, wide)	5.69 g
Rubber band (thin, white)	3.5 g
Silver Camera (No memory card)	187.5 g
Styrofoam (Pink, 1.5 by 19 by 17.5 in)	200.3 g
Yellow Cord with buckle	106.5 g
Zip Tie (Black)	1.5 g
Zip Tie (long, multicolored)	1.16 g
Zip Tie (Short, multicolored)	.31 g
7 Packs of Handwarmers	379.86 g
Cut Styrofoam+Minno Thermo	102.12 g
Green Bottle (With cannon, grey "Hindenburg")	239.69 g
Total Pay Load for High Altitude	944.34 g = Approx. 2.08 lbs

Fig. 24. Weights, measured in grams, for all possible parts being 

applied to the camera rigs. Also included is the approximate total 

weight of the Hindenburg.  

This report only contains the details of the rig building there is more to the overall structure including how the rig is fastened to the balloon and how the balloon is handled.

We have obtained a kit from the website mentioned previously. the kit contains a large balloon, ties, a ring, carabiner and the rope to tether and guide the balloon. A large ring is placed over the nozzle of the balloon before filling. The balloon is then filled with helium, due to size differences we have to manufacture a nozzle to fit from the helium tank to the balloon nozzle. After filling the balloon the nozzle is folded back on itself with the ring secured in the fold. above the ring the nozzle is secured with cable ties. From the ring the tether rope will be fastened using a carabiner. There will also be another carabiner with a large fishing type of swivel suspended from the ring, the camera rig will be connected to the swivel. the carabiners make attaching and releasing the rig much easier. The camera rig will be suspended from the swivel which will allow it to move free of the balloon. The balloon tether is controlled by a person on the ground who will manipulate it around the area being mapped. Much of this may be adjusted as we have not fully worked out the flight details.       

Conclusion:

Throughout this period we were able to think freely and try new ideas or improvements to existing ideas. . It is always better to be proactive rather than reactive; if you are in a situation where you have to react you are likely undoing a lot of damage that has already been done or are redoing a lot of work that was not completed correctly the first time. Trying to think ahead and figure out what might be needed with a project or what could possibly go wrong when you are in the field is essential. Proper preparation may help you look ahead and stop some problems from occurring before they happen you, saving you time in the end

Scale surface terrain model, digital elvation surface

Creating a digital elevation surface created from a surface terrain model.

Introduction:

This activity included using the XYZ data obtained in our first scale model exercise to build a digital elevation surface using Arc map and Arc scene  We tested several methods within Arc map to create a three-dimensional surface and then used Arc scene to display the results. We studied our outputs and determined what changes we could make to improve different steps of our methods. Finally, we used the new data to create a second set of XYZ data to map an updated version of our terrain surface model. Data for this exercise were gathered from a planter box located in the courtyard of the Phillips Science Hall at the University of Wisconsin Eau Claire; in Eau Claire, Wisconsin.

Methods:

Fig.2. Digital elevation model using
Kriging method of transformation. 

Fig.1. Digital elevation model using
 IDW method of transformation. 

We used Arc map to import the xyz data from our first model as a shapefile into a file geodatabase. We converted the data using several methods of 3-d analyst; including, IDW (figure 1), Spline, Natural neighbor, TIN and Kriging (figure 2). We imported several of these models into Arc scene to view them in 3-d. While analyzing the model data and 3-d conversions from the first model we decided the Kriging method best represented our data.

Fig.3. New snow covers the planter box containing the terrain model.

The planter box we used to build our model was the second box to the east of the north/south sidewalk which runs through the courtyard. The box measured approximately 1.2 meters wide by 2.4 meters long. The depth from the top edge of the box to the soil level was approximately 10 centimeters, but did vary somewhat throughout the box. Due to the frozen nature of the soil the model was constructed with snow which was readily available. For the creation of the original model the snow was scraped from the southern portion of the box to reveal a large flat area. That snow along with snow gathered from around the courtyard was used in creating a sizable formation in the center of the box. This formation was shaped into hills, a valley and mountainous ridges. Near the other end of the box we simulated a plateau with a gorge cutting through it. Since the construction of the first model we received about ¾ of an inch of new snow (figure 3) and there may have been some melting of the model. We used the new snow to reshape the existing model.

Fig.5. The terrain model with north/south
parallels at 5 cm increments.

Fig.4. Pins were placed every 5 cm
across the north and south ends of
the box.

We used the south/west corner of the box as our point of origin for gathering data. We measured five centimeter (cm) points across the north and south ends of the box (figure 4), beginning at the side of origin, inserting a pin at every point. With these points we were able to run a series of parallels on the north/south (x) axis at five cm intervals. The parallels ran up over the high points in our terrain (figure 5). Many of them touched the terrain so we measured the parallels at the points of contact to ensure accuracy. We then measured the east and west sides of the box, beginning at the side of origin, using a pencil to mark off five cm increments. To overcome the model being higher than the sides of the box we used two pieces of available 2x6 lumber to increase the height of the east and west sides of the box by fifteen cm.

Fig.6. Measuring the distance from the
cross stick to the terrain model. By adding
2x6 sides to the box we gained enough
 height to clear the terrain model.

Fig.7. One of the corner blocks
which stopped us from measuring the
height in the corners. 

We placed a meter measuring stick on top of the 2x6 at one end and moved the boards down the length of the box by our premeasured five cm increments. As we moved the stick and boards down the length of the box, beginning at the point of origin, we measured the distance from the stick to the terrain at every point the stick crossed a parallel on the x-axis (figure 6). The data were recorded by hand in a notebook in row, column format as follows: Y₀,X₁, X₂, X₃…, Y₂,X₁, X₂, X₃…, all vertical measurements were made to the nearest cm. Data collection we were unable to get the data points immediately in the corners of the box due to an obstruction used in building the box (figure 7). After collecting all of the data we removed all tools used in the process. The data were entered into an excel spreadsheet in the same form as by hand. The single missing data points at each of the four corners of the model were obtained by averaging the three points surrounding the missing point and rounding that value to the nearest whole cm. We used the highest value in the spreadsheet to determine the lowest point in the model; we subtracted each value in the table from the lowest point value giving us positive elevation values. These data were then converted to a simple XYZ table of coordinates. We used the previously described process to build the digital model of the new data set.

Discussion:

Fig.8. Digital elevation model (10 cm grid),
 shown using Jenks classification set at 20,
and an adjusted color scheme.  

As in the first model we ran into trouble with our grid system. The parallels that ran north/south could run up and over the terrain but not the east/west. When we tried the string would slide down the hill created by the terrain and the parallels. By using the available materials we increased the height of the sides of the box enough to clear the terrain and accurately gather the data. Using the unattached boards presented another small problem, while moving them between measurements one might pull the other off of the box because they were connected with a string. For our second attempt at the model we used a meter stick so all of the parts remained free floating, if one part failed it did not pull the rest with it. After viewing the results from the first model (figure 8), we decided they were somewhat coarse so we increased the resolution of the new model by decreasing the grid size used for measuring from 10 cm squares to 5 cm squares (figure 9). This increased the number of data points by four times, increasing the time to gather the data but also increasing the quality of the final project (figure 10). The time involved in setup and tear down of this project was approximately 45 minutes and the time to gather the data was about 1 hour.

Fig.9. Digital elevation model (5 cm grid),
 shown using Jenks classification set at 20,
and an adjusted color scheme.

Fig.10. Digital elevation model (5 cm grid),
 shown using stretched color palette.

  Of the 3-d interpolation models used some worked better than others. The TIN method appears very blocky, with large triangles of terrain, hence the name.  IDW was another poor method the model appeared to have ‘dimples’ across it, I am not sure what causes this but it is unappealing. Kriging, Natural neighbor and Spline all worked well and gave us a good picture of the model; of these three we chose Kriging.

Conclusion:

The overall idea of this activity is good; we built our own model and measure it just as if it were a real world scenario. In the real world we may encounter difficulties which impede the success of our project. The use of this exercise to develop and understand critical thinking, methods and possible changes to our project that may have been unforeseen but allow us to be successful.

Our team, which included Mitchell Collins, Kory Dercks and myself worked well together as a team. Each was prepared to work, both with the tools needed to do the exercise and in the cold weather. We were easily able to navigate each other’s schedules and find the time needed complete the project. I enjoy being outdoors especially in the winter; however, the weather was an minor inconvenience, the temperatures during the first part of the exercise were below zero with a north wind.    

Scale surface terrain model

Creation of a Digital Elevation Surface.

Introduction:

The purpose of this activity was to build a scale surface terrain model and use techniques we devise to survey the model obtaining x,y and z(elevation) coordinates. The model was built using a planter box located in the courtyard of the Phillips Science Hall at the University of Wisconsin Eau Claire; in Eau Claire, Wisconsin.  

Methods:                                          

The planter box was approximately 1.2 meters wide by 2.4 meters long. The depth from the top edge of the box to the soil level was approximately 10 centimeters. Due to the frozen nature of the soil the model was constructed with snow. To create the model the snow was scraped from a large portion of one end of the box to reveal a large flat area. the snow was used in creating a sizable formation in the center of the box which was shaped into hills and ridges. Near the other end of the box we simulated a plateau with a gorge cutting through it. After construction of the terrain we determined the South-West corner to be the origin. We used a ten centimeter grid pattern to measure the elevation points. From the origin we measured across the north and south ends of the box inserting  a pin every ten centimeters. We used these pins to layout parallel strings across the length of the box. The parallels ran up and over the terrain. To counteract the elevation of the terrain exceeding  the box we used available lumber to effectively increase the height of the east and west sides of the box by fifteen centimeters. We marked these at ten centimeter intervals, pinned a string across the box on the top of the boards and moved them down the length of the box measuring elevation of the of the terrain at the intersection of the cross string and the parallels from the cross string height down to the terrain. After entering the data into excel I subtracted each of the elevation values from the largest value present (the deepest point in the model) to gain a working set of positive elevation values.


















Discussion:

One of the challenges of this project was overcoming the height of the terrain in the box. The parallels could be run in the north-south direction right over the terrain; but when we attempted to run the east-west string the change in elevation would push the string down the hill not giving us an accurate grid. The use of the  boards to increase the height of the east and west sides of the box allowed us to clear the model with an accurate grid pattern. Running the parallels was not a necessity, however it sped up the process. By investing a little more time up front to save a lot of time in the end.     

Conclusion:
We built a scale terrain model and effectively gathered the data we needed from it for later use. This exercise forced us to think on the fly and adapt to the situations presented to us. The critical thinking used on this project can be carried forward to other situations encountered in the field.