Have you ever wondered what beaches used to look like back in the day? If so, you are not alone. Folks interested in answering that question often look to historical maps, such as NOAA T-sheets. Downloading these maps is easier today than in the past, but it may not be obvious where to find them. This post will briefly discuss how T-sheets were created and where they can be downloaded.
The Shoreline Vectorization Project
I remember when the only way to get a T-sheet was to look up the T-sheet number on a paper map catalog and then submit an email request to a person tasked with distributing NOAA products. A CD with scanned T-sheets would magically appear on my desk a week or so later. Fortunately, the Shoreline Vectorization Project changed that process. This was a multi-year initiative that began in 1997 and ended abruptly in 2011. The project goal was to convert paper T-sheets and associated data to raster formats so that they could be made available on the internet. A secondary goal was to make the shoreline on these maps GIS-friendly. Unfortunately, only 48% of the T-sheets were georeferenced before the project ended.
How was shoreline on T-sheets delineated?
Shoreline was mapped by plane tables, aerial photogrammetric surveys, or a combination of both methods. Mapping using the plane table was done in the field using a field party that required at least four men; one man to carry the table and other equipment, two rodmen and one topographer. These men would conduct a preliminary reconnaissance of the area to establish geodetic control before mapping could begin. During the mapping process, the rodmen would walk along the shoreline setting a rod when the shoreline changed direction. The plane table surveyor would align the rod with an alidade (for sighting distant objects) and record that point. These series of points would then be connected to form the shoreline. Information about the surrounding terrain may have also been added to create a very detailed map of the coastal zone.
In the early 1930s aerial photogrammetric surveys, using calibrated metric-quality cameras, were introduced marking an important transition in the history of shoreline mapping. The advent of mapping from aerial photographs brought shoreline delineation from the field into the office, and increased efficiency.
Shoreline Manuscript, T-sheet or TP-sheet: What is the difference?
A shoreline manuscript is a broader term that can refer to a shoreline survey, topographic map, or planametric map. Shoreline surveys were assigned registry numbers of T or TP series. Although differences may exist between shoreline manuscripts, T-Sheets and TP-sheets, these datasets are colloquially referred to as “T-sheets” or “NOS T-sheets”.
What datasets are available and where can I find them?
- The complete T-sheet and TP-sheet Shoreline Survey Scan Archive, which contains 16,200 scans and index map catalogs, is available through the non-georeferenced NOAA Shoreline Survey Scans website.
- Descriptive reports contain information that cannot be depicted on the map. They can be downloaded at NOAA Shoreline Survey Descriptive Reports website.
- Of the 16,200 scans, 7,800 were georeferenced and made available through the Google Earth tool. There are no plans to georeference the remaining 8,400 scans and this tool is not maintained.
- Footprints of the georeferenced scans are available in a GIS shapefile that contains full URLs to the georeferenced images, world files, descriptive reports, and metadata.
- The georeferenced scans, vector shoreline and metadata can also be downloaded from the NOAA Shoreline Data Explorer website.
If you have a few minutes and are curious about what the coastal zone looked like in the past, you may want to download a T-sheet of your area of interest. I must warn you though: it’s easy for those minutes to turn into hours.