Generate a thalweg for an inlet
The primary usage is fairly simple:
thalweg --data <path/to/NONNA-10/data> --corners <path/to/corners.txt>
This is roughly equivalent to
thalweg --resolution 20 --prefix . --format dms --data <path/to/NONNA-10/data> --corners <path/to/corners.txt>
This will extract the source and sink from the file indicated by --corners and use them to extract a thalweg from the data provided.
thalweg will output the path to <PREFIX>/path.txt, and information that can be used to produce a section plot to <PREFIX>/section.csv.
The resolution argument controls how far the path segments will be from each other. A larger resolution will likely result in fewer points along the thalweg.
The --format option controls the output of the thalweg file.
dms is roughly the same format as the ASCII files from NONNA-10.
geojson will produce a 3D LineString object, where the depth is represented as negative elevation.
The provided section.py script can consume section.csv to produce a section plot.
python section.py /path/to/section.csv
The core algorithm takes as input a list of lat/long/depth elements, as well as a source (starting position) and a sink (ending position).
It computes the thalweg as the shortest path from the source to the sink through a graph representing the input bathymetry.
In order to incentivise taking deeper points in the graph, the weight of an edge from a node to its neighbor is defined to be max_depth - neighbor.depth + 1,
where max_depth is the maximum depth of any value present, and neighbor.depth is the depth of that particular neighbor.
The section information is produced using the distance between each point along the thalweg line. Each point is converted into the total distance along the thalweg, keeping the depth as-is.