Shoreline Mapping History

Shoreline Mapping in NOAA

NOAA's predecessory agency, Survey of the Coast, was established by President Thomas Jefferson in 1807 to survey the U.S. coastline and create nautical charts to enchance maritime safety, support commerence and trade, and ensure national defense. In 1878 the agency was given a new name, the U.S. Coast and Geodetic Survey (USC&GS), which it maintained until 1970 when it was replaced with the National Oceanic and Atmospheric Administration (NOAA).

Origin of the Coastal Mapping Program

The Survey of the Coast was founded to create “an accurate chart of every part of the coasts.” Each chart would be built from two types of surveys. The first was a nautical (or hydrographic) survey, which mapped the depths of coastal waters and off-shore hazards. The other was a topographic survey, which mapped the land, including the shoreline, natural and cultural features, and elevations above the sea. The work of creating these topographic surveys is known today as the NOAA Coastal Mapping Program.

The First “T-sheet”

The U.S. Coast Survey created its first topographic map in 1834. At a scale of 1:10,000 (or about 6.3 inches to one mile), the map covered the shore of Great South Bay on Long Island, New York, between the towns of Babylon and Patchogue. Coast Survey topographic maps eventually became known as topographic sheets, or “T-sheets.”

Plane Table Surveying

The first hundred years of shoreline mapping in the Coast Survey relied on a method called plane table surveying. The plane table was the best instrument for quick yet accurate topographic mapping. The first plane table crew of the Coast Survey drew its first shoreline map in New York in the fall of 1834. The next year, a second mapping party was formed. The number of parties grew as would their progress in mapping the coast. By 1855, 540 topographic survey maps, scattered throughout the Atlantic, Gulf, and Pacific coasts, had been completed and registered. The plane table continued as the primary method of mapping the coastline for the next 80 years.

Aerial Photography

By the late 1800s, photography was recognized as a useful tool for mapping. In 1919, C&GS started work with the U.S. Army Air Service to investigate using aerial photographs to compile coastal topography. The Air Service provided the aircraft, pilots, cameras, photographers, and developing services. The first project covered the area around Atlantic City, New Jersey. Many photographs, on both glass plates and roll film, were taken using two different cameras. Overall, this first photographic mission was considered a resounding success. In 1920, the whole outer coastline of New Jersey was photographed and the photos were used to revise New Jersey coastal charts. Topography from aerial photographs was accurate enough to revise coastal charts for about one-third the cost of plane table methods and could be used to map areas where use of a plane table was problematic. Then in 1921-1922, C&GS conducted a major aerial photo survey of the Mississippi River delta. The plan was to create original topographic maps—not just revisions—from the photographs. The success of the project proved that aerial photo mapping could replace the plane table, depicting more detail at lower cost. Additional aerial photo surveys were flown in Florida (1926-1928) for chart revision, and the success of these projects led C&GS to expand a program for topographic mapping through aerial photogrammetry (the science and art of making accurate measurements from photographs). To support this program, the Photogrammetry Unit, under the Division of Hydrography and Topography, was established. This Unit eventually evolved into today’s Remote Sensing Division of NOAA’s National Geodetic Survey. Early air photo projects used single-lens cameras. These cameras were simple to operate and produced good pictures. However, in 1935, the agency built a precision nine-lens mapping camera. A multi-lens camera could take several photos looking down toward the ground at different angles. For the next 25 years, the nine-lens camera provided extensive aerial photo survey capability. Since the late 1930s, aerial photographs have become the primary source for shoreline information on nautical charts.

Nine Eyes are Better than One: Multi-Lens Cameras

Early air photo projects used single-lens cameras. These cameras were simple to operate and produced good pictures, but they had very narrow fields of view that required many photographs to cover a moderately sized area. Photos taken at a higher altitude covered more ground area in each image, but at reduced detail. The solution to this problem was to use cameras with multiple lenses. A multi-lens camera could take several photos looking down toward the ground at different angles. Since the multiple photos were all taken at the same time from a single camera, they could be combined into a single composite image that covered a much larger area of ground, effectively increasing the camera’s field of view. Early on, the C&GS used the multi-lens cameras of the U.S. Army and Navy. Projects were flown using three-, four-, and even five-lens cameras. However, C&GS soon realized that the available cameras were not accurate enough to support the high precision required for topographic mapping. In 1934, C&GS completed designs for a precision nine-lens mapping camera. The camera was built in 1935, although it would take several more months of calibration and adjustment before it was ready for mapping. For the next 25 years, the C&GS nine-lens camera provided extensive aerial photo survey capability. It was truly a unique instrument (the only one ever built) that paid for itself many times over by reducing the need for expensive ground control operations associated with traditional topographic mapping. It was only taken out of service for two years to be rebuilt, following a deadly crash in Alaska in July, 1943. The nine-lens camera was used for the last time in 1961, after having taken 141,000 photographs in all of the coastal states and several island territories.

Color and Infrared Aerial Imagery

During the 1950s, aerial cameras capable of taking color photographs were introduced. Color photographs were more natural looking than black and white photos, which made the identification and interpretation of various features in the image much easier. With the appropriate filters, color photography could also show underwater features more clearly, making it possible to identify and map submerged rocks, reefs, and shallow areas. These new cameras were also able to use film that was sensitive to near infra-red (IR) light. Near IR light reflects strongly from vegetation and dry ground, but is almost totally absorbed by water. Black and white IR photographs show a sharp contrast between land and water, making it easier to accurately identify and map the shoreline in the photograph. The line on the ground separating the land from the water (i.e., the shoreline) moves with the tide. Nautical charts depict the shoreline during mean high water (MHW), which is the average height of all high tides measured over many years. In order to accurately map the MHW line from IR photography, photos had to be taken during high tide. The first tide-coordinated IR photography for coastal mapping was obtained over Cobscook Bay, Maine in 1956.

Digital Aerial Imagery

Digital cameras have replaced film-based cameras. Digital aerial cameras increase the speed of availability of aerial photographs. One of the greatest benefits of digital cameras comes from their direct georeferencing capability, which allows camera position and orientation to be determined automatically using Global Positioning System (GPS) and inertial measurement unit (IMU) technology. Digital aerial cameras also provide imagery that is more sensitive to shadows and low illumination levels than film photography, and digital cameras typically acquire data in both visible and near-infrared bands. The improved radiometric performance of digital cameras enables significantly better accuracy of image classification.

Lidar

Light detection and ranging (lidar) is an active remote sensing system that uses pulses of light. Development of lidar technologies began in the late 1960s and became available for commercial topographic mapping in 1993. NOAA, in collaboration with NASA and the U.S. Geological Survey (USGS), has been mapping the shoreline using lidar since 1996 and continues to do so as technological advances in lidar mapping evolve. Lidar data collection involves mounting an airborne laser scanning system onboard an aircraft, along with a kinematic Global Positioning System (GPS) receiver to locate an x, y, z position and an inertial navigation system to monitor the pitch, roll, and heading of the aircraft. By accurately measuring the round-trip travel time of the laser pulse from the aircraft to the ground, a highly accurate spot elevation can be calculated. The National Geodetic Survey (NGS) has lidar into their shoreline mapping production process.

High Resolution Satellite Imagery

NOAA began evaluating high resolution commerical satellite imagery for coastal mapping over 20 years ago. As image resolution and geospatial accuracy improved, NOAA started compiling shoreline in 2006 using the best available commerical satellite imagery at the time. Today, imagery from commerical satellites is utilized for expedited shoreline requests and for situational awareness.