Balloon Mapping I - Preparation

Introduction

Satellite images and aerial photography are used for mapping purposes mainly by government institutions and people in power. Thus, the general public usually depends on their releasing information, which can be distorted by different interests, since the obtainment of satellite and aerial photography is expensive. Also, the images are usually out of date and do not represent the current status of the land. Alternative sources as Google Earth are valuable; however, they’re not systematically collected nor released which doesn't meet the scientific purposes of a project.  

The Balloon Mapping Method consists in using a camera in the continuous mode elevated by a helium balloon to acquire aerial images of the surface. It’s a low-cost alternative to obtain updated and specific data of an area with a reasonable level of detail. In this project, the class is working together to build and organize the balloon mapping and the later High Altitude Balloon Launching.

Methodology

Figure 1 - Payload Weight

Different kinds of materials were gathered and the students had to find out, using their creativity and some tutorials available, how to create the equipment properly to flight with the appropriate conditions. There was different areas working separately with the construction of a mapping rig and of a High Altitude Balloon Launch (HABL) rig, testing the parachutes, weighting the payload of both HABL and mapping rig (Figure 1), designing and implementing continuous shot on the cameras, as well as implementing and testing the tracking device and planning how to fill the balloon and securing it to the rig.

Whereas the students divided themselves in different groups with different purposes that will be connected at the end, this report focuses mainly in the construction of the mapping rig as well as the design of implementing continuous shot on the cameras. The specific goal for this section was to build a structure that properly protect the camera in case of a fall, without compromising the picture frame and guaranteeing the continuous mode with an automatic trigger.

Initially, the continuous mode needed to be found and evaluated in the available cameras. The type of picture taken and the shooting rate had to be considered to find the most appropriate mode for shooting. Plastic bottles were used to be the main protection for the camera; however, since there were different sizes of cameras and bottles, it was necessary to find the proper match between them.

Having that, duct tape, strings and rubber bands were used to hold the camera inside the bottle in a way it wouldn’t fall, but keeping in mind that the bottle must not appear in the picture frame, reason why, tests were made to guarantee that. Also, the permanence of the continuous mode depends on a trigger that keeps the button hold for the whole flight. Thus, the use of small eraser pieces and a knot in the rubber band were tested to find which one would work better to maintain the mode active.

Discussion

Firstly the continuous mode was being tested in three cameras. Since they have different software templates, this setting was displayed differently in each camera, thus, it took some time to set all of them in the same mode. 

After a size match with a two litter soda bottle, only one camera was the focus to further adaptations. The camera fitted inside the bottle tightly, reason why it was tested inside a bigger bottle as well, however, in the last one, since there’s more space available, the movement of the camera is increased, which can be cause blur in the pictures.

Figure 2  -  Second and bigger rig, it's possible to notice the space inside it, where the camera can move around.

Hence, there’s two options and their pros and cons: the first rig can provide stability of the camera, minimizing the blur of the movement, but the protection is minimized because it directly contacts the plastic; in the other hand, the second rig (Figure 2) can provide full protection, but the movement of the camera is higher, as well as the blur in the pictures. More tests related to the safety and picture quality have to be done to judge which one is more appropriate for the project purposes.

Something similar happened with the design of a trigger for the shooting button. At first, a small piece of eraser was used together with the rubber band to push the button continuously. However, with the strong pressure of the rubber band, it kept falling off repeated times. Then, it was decided to create a knot in the rubber band and test if that was enough to keep the button pressed, what resulted in a more convenient design. The only challenge in both cases was to deal with the zoom tool of the camera, placed together with the shooting button (Figure 3). All the times that the rubber band is being placed on the button, it activates the zoom mode, which is something not intended for the project. Hence, caution is necessary when activating the camera for shooting, so it doesn't activate the zoom as well.

Figure 3  - At the left, the eraser trigger causes prominence of the rubber band  on the button location, while at the right, the knot pushes the button without excessive pressure. In both cases, it's possible to notice the zoom tool attached to the button.

Conclusion

For the purposes of testing, planning and defining which materials and designs are more efficient and appropriate for the mapping and launch, the exercise was successful, although it’s necessary more adjusts and connection between each different section. It was a great exercise to organize a big group in a singular goal. The division of tasks worked effectively, yet not being totally separated: since everyone was together working at the same time, it was possible to presence other’s plans. Also, the flexibility and freedom to create the design for the rig exercised creativity by the trial and error of different ideas.

Though the exercise consisted more in planning the future mapping than actual collecting data, it’s important to realize the meaning of this project as the possibility of acquiring high resolution and significant images by the general population, instead of being concentrated only in positions of power. In this case, it’s only being used cameras with the visible portion of the electromagnetic spectrum, but the near infra-red could be used as well. Digital cameras are able to detect reflectance coming from this portion of the spectrum, but the manufacturers intentionally insert a NIR filter inside it. Its removal involves more complicated and technical – yet possible – procedures with the camera, reason why it was not included initially in this project. However, it’s an option that would give even more information, for instance, to detect vegetation health. Therefore, this project shows how the technical geographic knowledge allied with the creativity can enable the obtainment of valuable and extensive data with simple equipment.