The design of many projects begins with a depiction of the environment within which these projects exist. This depiction often takes the form of a rectified aerial photograph and a topographic map to aid the civil engineer during the design process. The Wild Animal Park, habitat restoration such as Goat Canyon and the Tijuana River Estuary and countless master-planned communities are all Rick Engineering Co. endeavors that began with aerial imagery and topographic mapping from its Photogrammetry Division. The civil engineer uses this information to plan and develop communities, the environmentalist uses this information to restore wetlands and other natural reserves and the transportation engineer uses this information to design freeway infrastructure.
The American Society for Photogrammetry and Remote Sensing defines photogrammetry as "the art, science and technology of obtaining reliable information about physical objects and the environment through the processes of recording, measuring and interpreting photographic images." Our company, founded in 1955, has always appreciated the value of photogrammetry and the importance of reliable information for engineering design. This was exemplified in 1972, when Rick Engineering created its own Photogrammetry Division.
Topographic mapping is a precisely created drawing of features such as roads, buildings, utilities and other permanent features that represent the same features on the Earth. The design engineer also needs to know the 3-D configuration of the ground. This third dimension is shown on the map as contours. Underlying these contours is a network of triangles known as a digital terrain model that mathematically represents the Earth's surface. Photography may be in the form of a simple aerial image; it may also be transformed into an orthophoto -- a scaled, rectified photo potentially as accurate as a map. The Photogrammetry Division has a sophisticated suite of tools to allow the photogrammetrist to transform digital aerial photography and precise measurements into accurate maps and orthophotos.
Once the region of the project and scope of tasks have been defined, the proper techniques and deliverables are determined. Project execution typically begins with the placement of white crosses, known as aerial panels, on the ground by the field surveyor. The surveyor accurately measures the mathematical relationship between these crosses by using Global Positioning System (GPS) techniques. The photogrammetrist then flies over the site acquiring precise aerial photography. The distances between the crosses are measured in the photos and a relationship between these photos and ground is established. Now the photogrammetrist can begin measuring in a 3-D "virtual world" representation of the Earth's surface. The photogrammetrist wears special glasses in sync with the computer monitor so that the left eye sees only the left photo and the right eye sees only the right photo. By alternating these images in rapid succession, the virtual world is created. The operator enters into this world to measure all of the features normally found on the map. A small project may be captured by a single pair of photographs, while larger projects require hundreds of overlapping photographs.
The same photos used for the mapping are also used to create a digital orthophoto. Hundreds of photos can be combined, making a single orthophoto mosaic. Just a few examples of imagery usage include a backdrop to a geographic information system such as seen on MapQuest or Google Earth, 3-D perspective scenes for view analysis and exhibits for planning commission meetings.
Staying on the cutting edge of surveying and photographic technology has become a hallmark of Rick Engineering Co.
Submitted by Jas Arnold, PLS, of Rick Engineering