Bug `transect_timeseries` fix intersection point for multipoint

[2320sharon]

SDStools/src/sdstools/compute_intersections.py

Line 47 in 2eb4d5d

def transect_timeseries(shorelines_path,

Dan found a bug with the transect_timeseries function that causes the multipoints not be replaced for the same shoreline that intersected multiple transects. I posted the new code that will fix this issue

Short Version

• After intersecting the shoreline with the transect the row index was duplicated
• The code to assign a replace a multipoint intersection point with a single intersection point was updating multiple rows if the shoreline row index was duplicated

New Code

    # get points, keep highest cross distance point if multipoint (most seaward intersection)
    joined_gdf['intersection_point'] = joined_gdf.geometry.intersection(joined_gdf['geometry_saved'])
    # reset the index because running the intersection function changes the index
    joined_gdf = joined_gdf.reset_index(drop=True)

    for i in range(len(joined_gdf['intersection_point'])):
        point = joined_gdf['intersection_point'].iloc[i]
        start_x = joined_gdf['x_start'].iloc[i]
        start_y = joined_gdf['y_start'].iloc[i]
        if type(point) == shapely.MultiPoint:
            points = [shapely.Point(coord) for coord in point.geoms]
            points = gpd.GeoSeries(points, crs=crs)
            coords = points.get_coordinates()
            dists = [None]*len(coords)
            for j in range(len(coords)):
                dists[j] = cross_distance(start_x, start_y, coords['x'].iloc[j], coords['y'].iloc[j])
            max_dist_idx = np.argmax(dists)
            last_point = points[max_dist_idx]
           # joined_gdf['intersection_point'].iloc[i] = last_point # replace this line
           # This new line  updates the shoreline at index (i) for a single value. We only want to update a single shoreline
            joined_gdf.at[i, 'intersection_point'] = last_point # is only edits a single intersection point

Full Explanation

After intersecting the shorelines with the transects the row index is changed to the number of shorelines (0-255) and it is duplicated for every date. This means that for each instance the shoreline intersected a transect it is duplicated with the same index but a different intersection point. So it the shoreline intersected 5 transects there are 5 rows with the index 0.

joined_gdf['intersection_point'] = joined_gdf.geometry.intersection(joined_gdf['geometry_saved'])
# reset the index because running the intersection function changes the index
joined_gdf = joined_gdf.reset_index(drop=True)

The second issue was in the loop.

for i in range(len(joined_gdf['intersection_point'])):
    point = joined_gdf['intersection_point'].iloc[i]
    start_x = joined_gdf['x_start'].iloc[i]
    start_y = joined_gdf['y_start'].iloc[i]
    if type(point) == shapely.MultiPoint:
        points = [shapely.Point(coord) for coord in point.geoms]
        points = gpd.GeoSeries(points, crs=crs)
        coords = points.get_coordinates()
        dists = [None]*len(coords)
        for j in range(len(coords)):
            dists[j] = cross_distance(start_x, start_y, coords['x'].iloc[j], coords['y'].iloc[j])
        max_dist_idx = np.argmax(dists)
        last_point = points[max_dist_idx]
        # This line causes all the intersection points for the index i to be changed to the last point (BAD if the index is duplicated)
        # joined_gdf['intersection_point'].iloc[i] = last_point
        # This new line  updates the shoreline at index (i) for a single value. We only want to update a single shoreline
        joined_gdf.at[i, 'intersection_point'] = last_point # is only edits a single intersection point