Field Activity #10: Balloon Mapping of the Sports Complex

Introduction:

This activity's goal was to use a helium balloon with a 5 foot diameter to capture aerial imagery which could be used for mapping. This process is desirable as a form of unmanned aerial systems because it is cheap and easy to rig up for yourself. This process is very similar to the kite that was used in a previous activity, except that the balloon had less variation due to the fact that the wind was less of a factor for its movement than the kite. The imagery was collected at the Eau Claire Sports Complex which is very close to Bollinger fields. In order to get a finished and seamless product from the balloon's images they must be mosaicked together, georeferenced to the real world and orthorectified between differing programs. Many UAS have been looked at and used throughout the semester, but this may be the best yet for quality.

Methods:

The process of setting up for this is very easy. Before the activity can be replicated there are some basic needs in order to ensure the success of the mission. The equipment needed for this activity includes a balloon, helium tank, zip ties, reel and string, and a picavet rig which helps to hold up the camera and orient it over the earth's surface. The initial phase starts by filling the balloon with helium so that it can float. Once the balloon was filled the zip ties were used to seal the balloon so that it didn't release any helium. The string was also tied to the base of the balloon at this time.

Image 1: Here I can been seen inflating the helium balloon and preparing it for flight over the Eau Claire Sports Complex.

Image 2: The image above shows Blake, Nate and Professor Hupy rigging the picavet device to the string. Blake is holding the reel that has the string wrapped around it as well. The balloon was nearly ready for flight at this point.

The next step in the balloon imagery process is to connect the picavet rig to the string. The rig carries two cameras and a GPS device which is used to tie the images to a specific GPS location. The cameras that were attached were a Canon SX260 and a Canon Elf. The picavet was then lifted into the air to 500 feet. We, as  a class, then walked around the field holding the balloon which was continuously taking images.

Image 3: The image here shows the picavet rig being attached to the string by Professor Hupy. The image shows both cameras and the GPS unit.

Image 4: The image above shows the picavet attached to the string of the ballloon being rained to 500 feet. The rig was just over 30 feet in the air when this image was taken.

To ensure image quality the class agreed upon a route which zig zagged across the fields. This would create less overlap, and cover a broader area for image collection. We walked for nearly 200 feet then hung a 90 degree turn which lasted another 200 feet where another 90 degree turn was made. The cameras each took quite a few pictures. The Elf took 352 pictures while the SX260 took 494. Once the images were collected the hard part ensued.

Photoscan:

The instructions below were provided by my classmate Drew Briski who put a lot of time into trying to figure out how to use the software.

1. Open PhotoScan
2. On the Tab list click Workflow
3. Click Add Photos (only use the photos you want, if to many are used (~200) the process will take hours to complete)
4. Add the photos you want to stitch together
5. Once the photos are added go back to the Workflow tab and click Align Photos. This creates a Point Cloud, which is similar to LiDAR data.
6. After the photos are aligned in the Workflow tab, click Build Mesh. This creates a Triangular Integrated Network (TIN) from the Point Cloud.
7. After the TIN is created from the mesh, under Workflow click Create the Texture. Nothing will happen or appear different until you turn on the texture. 
8. Under the Tabs there will be a bunch of icons, some of them will be turned on all ready, but look for the one called Texture. Click on it to turn it on.
9. If you want you can turn off the blue squares by clicking on the Camera icon.
10. In order to export the image to use it in other programs; Under File, click Export Orthophoto.  You can save it as a JPEG/TIFF/PNG. It's best to save it as a TIFF.
11. With the photo exported as a TIFF, open ArcMap and bring in the TIFF photo and bring a satellite photo of Eau Claire or use the World Imagery base map.
12. You will only need to Georeference the photos if the images you are using were not Geotagged. Open the Geoprocessing Tool-set.
13. Click on the Viewer icon.  The button with the magnifying glass on.  This will open a separate viewer with the unreferenced TIFF in.
14. Click Add Control Points. The control points will help move the photo to where it is suppose to be.
15. With the control points click somewhere on the orthophoto, then click on the satellite image in ArcMap where the point in the unreferenced TIFF should be.  Keep adding control points until the photo is referenced.  The edges of the image will be distorted.  Don't spend too much time adding control points there.
16. The next step is to save the georeferenced image. Click on Georeferencing in the toolbar. Then click Rectify from the drop down menu.  You can save it wherever you need it.
17. The next step is to embed the GPX track log into the images.  For this the programGeosetter was used. 

Geosetter:

1. First you will need to open the images that you will want to use. The photos will go into the viewer box on the left side of the screen. Look at all the photos and make sure there are not any blue markers on them. If they have black/grey they have lat/long attached to them.
2. You will click the button with 2 on.  this allows you to select the trackfile that you want to embed in the images.
3. A window will open. Click Synchronize with Data File. Input the GPX track log.

Image 5: The image here shows the initial steps of the Geosetter software.

Image 6: The image provided here shows the user how to save the images in the Geosetter software.

Results:

Image 7: The image here shows the final results from using Photoscan and Geosetter. The final product is also georeferenced and can be used in ArcMap as imagery. 

Discussion:

Prior to beginning this exercise Professor Hupy forgot one of the camera's SD cards which holds the key to saving the image that the camera takes. Professor Hupy and another student then went back to the campus to grab the SD card. If this occurred in an actual workplace then the missed time could have cost money which could have cost the team its job. Mission planning as a group is key for success.

Some image didn't come out very well because picavet rig was swinging quite a bit due to the gusting of the wind. Good images were collected though and used in the creation of the final product which can be seen in image 7 above.

Conclusion:

In conclusion, a balloon is a cost effective way to use UAS. While it may be one of the cheapest ways to collect data, it has its pitfalls as well. For example, when the picavet was swaying it took terrible pictures which caused some bad imagery to be made from those photos. More mission planning as a class could have been done and should be done in the recreation of this project to ensure more time in the field taking more images. Much like all UAS the balloon as its ups and downs, but is overall a great tool for someone on a budget.