Comprehensive Survey of Carolina Bay Landforms

A detailed survey of all Carolina bays is underway here. The “Quadrants”, which are 1º of Longitude wide and 1º of Latitude high, as currently described by the USGS, are our top-most organizational element.

The Map show below is interactively driven by a Google Fusion table. The purple rectangles identify octants to be surveyed, and link to low-resolution 1/3 arc-second (~10 ft grid) DEM imagery at the 1º Quadrant level. Clicking on one of these placemarks will bring up a bubble with links to return the KML metadata file to your computer for viewing in Google Earth. Those quadrant KML files are hsv-shaded maps created from USGS’s “The National Map” 1/3 arc second DEM - ~10 ft gridded data points.

In order to provide reasonable sized elements for high resolution LiDAR-quality maps (1 to 3 meter grids), we have subdivided each quadrant into sixteen )16) “Octants” (our term). The live Google Fusion map below identifies these 1/4 degree “octants” (yellow placemarks) and those currently populated by LiDAR-quality imagery (green placemarks). These efforts are being undertaken to expand on the LiDAR imagery available in the predecessor “Fields” project. Due to the numerical count of these landforms, we are looking for collaborators who would be kind enough to annotate our Google Earth Octant meta data structures with their observation of bay locations. Clicking on one for any of these placemarks will supply the user with a starter KML file to work with for that 0.25º x 0.25º octant..

Our goal is to gain a better understanding of these enigmatic landforms by collecting numerous statistics about their location and shape, and by correlating that data to see if any clues as to their nature can be gleaned from those analysis. For example, by capturing the major and minor axis lengths of the oval bays, we can see how their ratio varies with overall size, and how it varies by latitude and longitude. The following graph shows such a plot for bays in the North Carolina area.

By sampling the bay area sizes and plotting the numerical count as a histogram, we can understand the distribution of bays by sizes. The following graph summarizes about 4,000 bays.

Histogram of the distribution of bays by area size

Structure of the KML File

Each 100K Quadrant is described in a kml file named with the standardized USGS 100K Quadrant name. The following graphic show the DOM of Google Earth Elements in a given survey 100K Quadrant ( Camden ), including the eight Octants and contents thereof. The Octant naming system is generated using the bay’s latitude & longitude, on a 0.25 degree grid. LiDAR is available as either “full”, or “part”, in which the overlay drops out when below ~3KM eye altitude. This makes comparing bay planforms in the LiDAR with its visual presence in Google Earth’s satellite imagery easier. The 4-digit “bay” number (vvhh) is similarly derived from the latitude and longitude, this time referencing 100 vertical grids and 100 horizontal grids (10,000 possible locations within each octant) in which the bay’s central point lies. Bay planform overlays are sourced using the Google Fusion Tables facility, by way of a query of a cloud-based data structure.

Google Earth DOM

The bay meta structure is created as output from a custom coded java program. The input to this program is simply a folder of our bay planform overlays, oriented and sized to represent the actual bay, as the user interprets it. Should you be interested in participating, please access THIS page, which discusses the programs.

Our earlier survey of Carolina bay landforms was carried out using a "field-based" approach, with the count of fields approaching 250. These can be viewed using the
Distal_Ejecta_Fields.kml file. These fields are randomly sized, done in an attempt to keep their sizes down to the absolute minimum, especially when the 1-9 arc-second data is used. But the random sizes are presenting challenges as we attempt to count all the bays...

Most of the larger field DEM files have been recently further reduced by removing the tiles for the highest resolution. It also allows for the user experience of toggling the DEM image off when zooming in very close to the earth - which then allows for viewing of the Google Earth imagery for comparison purposes.

Survey Overlays by Region

Our survey of bays utilizes a stylized overlay shape to capture bay orientation and size metrics. The shapes are seen as changing in a systematic way as the ejecta annulus is traversed clockwise from New Jersey. The following graphic displays the overlays in the following order: NJ, NY and Delmarva’s bayBell; VA & Delmarva’s bayOvall and bayShore; most common bayCarolina; South Carolina’s, Georgia and Alabama’s baySouth; Nebraska’s bayWest.

Pasted Graphic 1

Here is a Fusion Table Visualization that displays the distribution of each of these Archetypes.

Next is a scatterplot of bearings vs. latitude and bearings vs. longitude for the eastern bays (Nebraska excluded, as it orientates normal to the Eastern bays, given the Saginaw focus). This is a live Fusion table visualization.

Finally, here is a sample of the visualization of results on the Google Earth Virtual Globe, using their plug-in technology.

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