Acknowledgments

Jennifer Fowler, University of Montana, Flight Director UM-BOREALIS

Mindy Mason, BLM Geologist

Dr. Marc Hendrix, University of Montana Geosciences Department

Jill King, Project Videographer

Jim Sheldon, Ice Age Floods Institute ,Lake Missoula Chapter President

Introduction

The focus of this project is on the integration of a three-dimensional camera system and a tethered balloon to attain stereoscopic photographs of the prominent glacial ripple marks in Camas Prairie Montana. Salish Kootenai College has collaborated with and has been instrumental in securing land permissions needed for the project. Our objective with the UM-BOREALIS tethered balloon is to create a three dimensional image for a digital elevation model (DEM) of these ripple marks left over from Glacial Lake Missoula. In 2011 stereoscopic images were taken in the area, but at too low resolution and did not achieve the desired geospatial accuracy and precision of ±.5 feet. Mapping these ripples will provide useful and new data to geologists reconstructing past global scenarios as well as interdisciplinary scientists modeling fluid flow. Furthermore, as our imaging capabilities stretch further into space the use of digital elevation models (DEM) as a comparison model to the mapping of other planets, particularly Mars, has become a necessity. This poster will outline previous work done on the project and future enhancements to be initiated this summer.

RIMM-CAPP(Ripple Mark Mapping – Camas Prairie Project)

Katie Roskilly, Ed Kleinsasser, Fred Bunt Dept. of Physics and Astronomy, University of MontanaSean Lodmell Hellgate High School, Missoula, MT

Image Processing Methods

Two main software programs will be used to process the images from the camera system, Photosynth and ArcGIS.

•Photosynth: Photosynth uses an algorithm to remove photos it determines as outliers, chooses points of interest in photos and match them to the same points on other photos, and creates a 3D point cloud. A point cloud is simply a set of vertices in space that represent the surface of a desired object. An arbitrary coordinate grid will be assigned to ground control points in the overlaid images. This process requires about 800 photos. This number of photos is required by Photosynth to find matching features in at least three separate photos taken from different locations and to limit angles between photos, about one photo every 25 degrees, to make the synth work better.  . •ArcGIS: Once the 3D point cloud is generated from the overlay, the points are put into ArcGIS. This program transforms our point cloud into real world coordinates and creates our DEM. This system will be replicable at a fairly low-cost, minimal production level, lending to the possibility of use by other learning institutions or scientific facilities.

Figure 2: DEM above from point cloud displayed to the right.. Pink is a lower elevation than green. Approximate location of this area is 47.5365 latitude and -114.607 longitude with an average elevation of about 3000 feet. The DEM is currently displaying an arbitrary coordinate system and should be projected to a known coordinate system for mapping purposes.

Figure 3: Point cloud overlaid on Bing map of area.

Figure 4: Photosynth point cloud from August 2011 launch.

Imaging MethodsThe camera system consists of two Casio EX-H20G, 14.1

megapixel cameras mounted to a tethered balloon. A converging axis will be implemented to obtain low post-production three dimensional images.

A circuit will be wired to both cameras to allow remote shutter to ensure proper image capture timing. Remote image monitoring will be implemented to ensure the proper range of photographs are taken on every flight.

The camera system will be leveled using a Picavet suspension equipped with PeKaBe ball-bearing blocks. The suspension consists of a rigid cross suspended below the balloon from two points. A single line will be threaded several times through eye-hooks connected to pulleys allowing the weight of the rig to settle naturally to a level position.

The two cameras will take images at 60% overlay. To get a map scale of 1 inch: 600 feet, with a camera of focal length 24-240mm, the tether would have to be about 40 feet above ground level.

We will us at least 9 ground control points, GCPs, in our field of view. To calculate field of view we use optical formulas. For these we need image size, d, and this could be defined by the a flat panel screen we use to identify GCPs in the image, as well as angle of view from the camera lens (see Image Processing Methods).

The size of individual GCPs will be 6X8 foot tarps to create a 3X3 grid and have 40 foot spacing between GCPs. The GCPs must also be contrasting colors in order to be seen in the later generated point cloud. The GCPs will be used to assist in bringing our arbitrary coordinate grid, generated by Photosynth, into real world coordinates.

Figure 1: Tethered balloon photographed from ground.