NOAA's use of remote sensing technology and the coastal mapping program

Abstract

Advancements in acquiring bathymetry and capturing features below the water's surface have significantly improved our knowledge of what lies beneath rivers, lakes, and oceans. Surveying techniques utilize methods such as multibeam, side scan sonar, laser scanners, satellite derived bathymetry (SDB), and topographic-bathymetric (topobathy) lidar. Of these methods, bathymetric lidar is becoming the emergent sensor of choice to survey nearshore bathymetry (0–4 meters typically).NOAA's National Geodetic Survey (NGS) collects a variety of remote sensing data using both traditional and emerging technologies. NGS products include: topobathy lidar datasets, aerial photographs (nadir and oblique), the National shoreline, and Continuously Updated Shoreline Products (CUSP).Topobathy lidar is flown on a small aircraft at low altitude following predetermined flight plans and staging. Bathymetric lidar sensors provide an efficient, flexible, cost effective and overall safer method to acquire coastal bathymetry whereas multibeam can be utilized more effectively beyond the 4 meter depth curve. NGS operates the Riegl VQ-880-G topobathy airborne laser scanning sensor and surveys coastal shorelines, as well as monitors the spatial and temporal nature of nearshore bathymetry. Nadir imagery is also collected, orthorectified for viewing, and supports the construction of topobathy elevation models.NGS acquires aerial photogrammetry via a Trimble Digital Sensor Systems to independently verify shoreline changes and to aid topobathy lidar data collection. These high-resolution digital cameras are also used for emergency response to collect pre- and post-event (oblique and nadir) imagery which assist in response and recovery efforts along coastlines impacted by major events (e.g. Hurricanes: Harvey, Sandy, Katrina; Tornadoes in Joplin and Tuscaloosa; Midwest U.S. flooding and human-induced disasters like Deepwater Horizon, etc.). Coastal oblique imagery is especially important for emergency response because it is collected at a 35–40 degree angle to provide a view of a wider area; improving the visibility of vertical structures, such as the sides of buildings, as opposed to only the tops of buildings as typically seen in traditional imagery. NOAA acquires and rapidly disseminates these images to support homeland security and emergency response requirements. Additionally, several commercial sources have incorporated the aerial imagery into internet based map servers to provide search capabilities based on street addresses, city names and points of interest.At times, NGS must also utilize satellite imagery to monitor shoreline changes and generate derived products (e.g. CUSP and satellite derived bathymetry). These products are especially important for remote regions such as Alaska or small geographic areas where aircraft logistics and competing priorities make it challenging to maximize the utilization of NOAA's platforms. Satellite imagery provides a rapid analysis over a large area but is limited by imagery resolution, weather conditions, and water column quality.In this paper, we will describe the historical perspective of remote sensing in NGS, the different remote sensing technologies and products used today, and the outlook for optical technologies being explored for use at NGS in the future.