Baseline coastal oblique aerial photographs collected from Fenwick Island State Park, Delaware, to Corolla, North Carolina, March 27, 1998

Image Acquisition: Photographs were taken with two Nikon F3 cameras, each with a fixed 50-millimeter lens and a Skylight filter. One camera shot the odd-numbered film rolls, and the other camera shot the even-numbered rolls. Both cameras were equipped with a Nikon MF-14 data back. Rolls were numbered by hand in the air. Film used was Kodak Ektachrome E100G. Commonly used shutter speeds were 1/250 seconds or 1/125 seconds. A constant shutter speed was attempted but may vary if there was a noticeable change in light levels. The f-stop was changed to compensate for changes in light levels. The Nikon MF-14 data back added day of the month, hour, and minute (UTC) to the lower right-hand corner of the photo. All photographs were taken from the the open door of the aircraft. Independent of all other equipment, a Rockwell Collins PLGR GPS recorded navigation fixes, at a 30-second interval, acquired from a National Marine Electronics Association (NMEA) string during the flight. A Compix Titler unit provided video subtitles that include latitude, longitude, and time (Hour:Minute:Second). Navigation was provided to the video by a Trimble Centurion GPS receiver, and time was provided by the titler unit's internal clock, which had been synchronized with UTC time. The cameras' images are denoted by a "r###s##" in the filename. The images are labeled with the following filename format: yyyy_mmdd_r###s##.jpg, where yyyy denotes the year, mmdd denotes the month and day, r### is the roll number and s## is the slide number of the image. For example, image 1998_0327_r001s03.jpg was taken March 27, 1998, the first roll of the flight, the third slide.

The video and still photography were shot out of the open door of the aircraft. The video files are not included in this publication.

E6 Ektachrome slide processing was completed by Zebra Color Photo Lab in St. Petersburg, FL. Date, frame, and roll number were printed on slide mount. There is no roll number 4 in this data set.

Slide Scanning and Processing: Slides were scanned using a Nikon Super CoolScan 5000 scanner and Nikon Scan 4 software. The slides were scanned using Digital Image Correction and Enhancement (ICE) technology at a resolution of 3,000 dots per inch (DPI) and files were saved as 18.6-megabyte tagged image file format (TIFF) images. The TIFF images were then converted to JPEG images at a resolution of 3000 dots per inch using Adobe Photoshop CC. ICE technology automatically removes artifacts, such as dust and scratches from scanned images. Only JPEG images are included in this data release. The photograph names provide information about the photograph's year, date, roll number, and slide number. For example, slide 1998_0327_r030s01 was taken March 27, 1998, and is the first slide for roll 30. Slide names (year_monthday_roll numberslide number) and time (hour, minute) were manually entered into a Microsoft Excel Ver. 15 spreadsheet. A Nikon MF-14 data back marked the time each photograph was acquired on the lower right corner of the image in day, hour, and minute format. It is assumed, for the purposes of location, that the photographs were taken at a constant rate during any given minute of flight. To assign a time value in seconds to each photograph, the number of photographs taken during each minute was evenly distributed across those 60 seconds. For example: if 15 photographs were taken during minute 19:00, researchers assumed that a picture was taken every 4 seconds. The photographs were then assigned the time values 19:00, 19:04, 19:08, and so on. It should be noted that the positions assigned to each photograph are an estimate of the aircraft position, not the location of the landmark photographed. Photos were then reviewed in Google Earth and adjustments to their positions were made by hand to compensate for pauses during acquisition. During this flight the photographer did not make an effort to get overlapping imagery.

Navigation Files from GPS: Navigation files were extracted as comma-delimited American Standard Code for Information Interchange (ASCII) text files. The Rockwell Collins PLGR recorded waypoint_name, projection, latitude (degrees, minute, seconds), longitude (degrees, minute, seconds), altitude, datum, heading, and elevation relative to mean sea level for the entire flight every 30 seconds; however, no time was recorded. Latitude and longitude from the Rockwell Collins PLGR navigation files were converted from degrees, minutes, and seconds to decimal degrees using a custom Perl script written by K. Morgan.

Navigation File Interpolation from Video: Latitude, longitude (degree, decimal minutes) and time were manually extracted from the video using a custom Optical Character Recognition program written by script written by E. Dailey of the USGS Pacific Coastal and Marine Science Center. Latitude and longitude were converted to decimal degrees. Then the time was interpolated between these fixes to produce a 1-second time value record (hour:minute:second) for the entire survey and saved as the comma-separated value (CSV) file.

Processed Navigation: The values from the 1-second time value record for the entire flight were merged with the time estimates for each image to produce a latitude, longitude and time record for each slide. The processed navigation file was saved as a comma-separated value (csv) file, 98ACH02-Photolocations.csv, using Microsoft Excel Ver. 15.

Survey map creation: The survey maps provided in this archive were created with Environmental Systems Research Institute (Esri) ArcGIS 10.4 software and saved as Adobe Illustrator (*.ai) files. Survey maps were edited using Adobe Illustrator CC and exported in JPEG format.

EXIF headers: Exchangeable Image File (EXIF) and International Press Telecommunications Council (IPTC) headers were populated from the command prompt using ExifTool (http://www.sno.phy.queensu.ca/~phil/exiftool) ExifTool was executed from a directory containing all photographs to be edited and a CSV file with information for each of the photographs. The metadata values for photograph creation include time, GPS latitude, GPS longitude, GPS position (latitude and longitude), keywords, credit, artist (photographer), caption, copyright, and contact were added to each photograph's EXIF header using a Perl script written by K. Morgan.

Added keywords section with USGS persistent identifier as theme keyword.