Balloon Mapping I

Field testing the mapping and HABL camera rigs.

Introduction:

Previously we explored varying methods of suspending a camera beneath a helium filled balloon to do small scale aerial mapping. This week we tested two of the aerial rigs over the University of Wisconsin Eau Claire’s (UWEC) lower campus. One of the rigs tested was for use in the high altitude balloon launch (HABL). The other rig was similarly constructed but used for aerial mapping.

Methods:

The class was broken up into several groups today in order to complete several activities related to a successful deployment of the rigs. The group’s activities included; transport of the large helium tank from storage to the garage where the balloon would be filled, filling the balloon, measuring several hundred feet of tether line, assembly of the camera rig and photographing and videotaping of the activities.

The cylinder of helium was successfully transported (figure 1) from storage on the second floor, down one floor and around the Phillips Science Building to the garage without incident where it was used to fill a large balloon (figure 2). The balloon is the source of lift for the mapping rig.

Fig.1. The large helium tank had to be transported from storage to the work shed
where the helium was used to fill the balloon for mapping.

Fig.2. Filling the balloon was a team effort due in part to the size of the balloon.
A piece of rubber hose was used to pipe the helium from the tank into the balloon.

Approximately 500 feet of tether cord were measured out and marked in 50 foot sections so we could track the amount of cord being used and the approximate height of the balloon rig (figures 3,4,5).

Fig.3. 50, one foot floor tiles were used to measure out the tether cord. 

Fig.4. The cord was measured out to 450 feet and marked every 50 feet.

Fig.5. We marked the cord every 50 feet in order to track the elevation of the
balloon rig when it was used.

The camera rig used for the HABL project was modified to use for mapping due to the ease of use and overall stability of the rig comared to the bottle rigs (figure 6). This rig was simply a styrofoam bait box turned upside down with a hole in the lid for a camera viewport (figures 7,8). Then heavy cords were attached from the bottom around each of the four sides to above the rig where they were tied in a knot. The camera was fastened onto the inside of the lid with the lens in the viewport (figure 9). The camera used for mapping was set to take continuous pictures while deployed, the HABL camera was set to take video.

Fig.6. The original bottle rigs built for mapping were not used due to thier
instability in the air.

Fig.7. A rig very similar to the HABL rig was used for mapping.
The design of this rig was very simple and easy to use.

Fig.8. The HABL rig was tested using the balloon rig.
The testing was done to help eliminate any issues that
might arise in the actual launch. 

Fig.9. Both the HABL and the mapping rig were set up with the camera fastened
to the inside of the box lid with the lens looking through a viewport  in the lid.

After all of the individual parts were functional we assembled the rig. The tether cord was attached to the balloon using a large ring and a carabiner (figure10). From this point the mapping camera rig was also hung. We began in the campus mall area; this is an open space without overhead obstructions. We started the camera and slowly released four hundred feet of line out (figure 11). The rig was guided around the campus mall area (figure 12) and brought back in; this was just to test the rig. We then attached the HABL rig to the balloon and again released four hundred feet of line in the campus mall area. After guiding the rig around the mall we took it north towards the foot bridge and across the Chippewa River. After crossing the river we concluded our tests, prematurely (figure 13).  

Fig.10. After the balloon was filled the tether cord was attached using a
karabiner, the camera rig was hung similarly below the balloon. 

Fig.11. As students released the cord allowing the balloon to rise they were
watching for the marks on the cord which told them how much line
had been released.

Fig.12. As the balloon rig was guided around the
campus mall area these lamp posts were nearly the
only obstruction, there were also some trees near
buildings.  

Fig.13. This image was shot shortly before the tether cord broke allowing the
balloon to float off into the wild blue yonder and the camera rig to crash not
so delicately into the Chippewa River ending our test run. Note the position of
the balloon in relation to the bridge, the wind had a great effect on our success. 

The images we obtained from the mapping rig (figure 14) were sorted through and the best were used to create a map of the campus mall area. To make this map we used a TIFF image of UWEC campus as a base layer and georeferenced each new J-peg image in arcmap. After each image was georeferenced we used the mosaic to new raster tool to create a single image (figure 15).

Fig.14. This image was shot from our balloon mapping rig! Not all of the images
turned out so well, many were out of focus and not pointed directly at the ground. 

Fig.15. several of the better images were used
to make a mosaic of the area. This .tif image
is the result of the mosaic process with our
aerial images.
 

Discussion:

This was a busy afternoon with cooperation needed buy all involved, that said it was moderately successful. We were testing the equipment in less than desirable conditions and the wind was an issue (figure16). During the mapping test the wind caused the balloon to bounce and move only slightly; however, the camera rig was buffeted severely causing several images of the horizon and not the ground. The wind also caused the rig not to reach its full height, even though we had four hundred feet of line out the rig was only about 150 feet off of the ground. The test with the HABL rig was similar right to the end. After crossing the river we experienced a significant equipment failure. Something in the area of the balloon either the tether cord or the balloon itself failed. After the failure the balloon floated of into the approaching dusk and the camera rig plummeted into the Chippewa River. The design of the rig saved it, the camera was waterproof and more importantly the foam bait box floats on water. After landing on the water it floated near the edge and was retrieved as it passed near the foot bridge using a long stick and a lucky grab (figure 17).   

Fig.16. The effects of the wind are apparent in this image, the rig is pointing
somewhere off into the sunset.

Fig.17. Professor Joe Hupy is hiking back up from the rocky shore of
the Chippewa River with his prize from a skilled grab with a 12 foot stick.
The design of the rig, using the foam bait box with its inherent buoyancy,
 certainly aided us in the recovery of our rig from the river

Conclusion:

Although we encountered some difficulties we learned some valuable information. Do not attempt in high or even moderate winds. Even in light winds the HABL construction may not be the best for the mapping rig. It is greatly affected by the winds causing it to spin and be tossed around very erratically. It was also interesting to see the first images from such a simple rig. Also, being a bit of a photography buff this may be an interesting method of taking photographs (figures 18,19).  

Fig.18. The windy conditions led to some interesting photos.
This image is looking north across Schofield Hall and up the
Chippewa River.

Fig.19. Due to the wind we were able to obtain probably the
most unique image of the new Davies Student Center on
the UWEC campus.