Plot LINESTRING Z from GeoDataFrame using pydeck's PathLayer (or TripLayer)

Question

I have a geodataframe with LINESTRING Z geometries:

	TimeUTC	Latitude	Longitude	AGL	geometry
0	2021-06-16 00:34:04+00:00	42.8354	-70.9196	82.2	LINESTRING Z (42.83541343273769 -70.91961015378617 82.2, 42.83541343273769 -70.91961015378617 82.2)
1	2021-06-14 13:32:18+00:00	42.8467	-70.8192	66.3	LINESTRING Z (42.84674080836037 -70.81919357049679 66.3, 42.84674080836037 -70.81919357049679 66.3)
2	2021-06-18 23:56:05+00:00	43.0788	-70.7541	0.9	LINESTRING Z (43.07882882269921 -70.75414567194126 0.9, 43.07884601143309 -70.75416286067514 0, 43.07885174101104 -70.75416286067514 0, 43.07884028185512 -70.75415713109717 0, 43.07884601143309 -70.75414567194126 0, 43.07884601143309 -70.75414567194126 0)

I can plot the component points using pydeck's ScatterplotLayer using the raw (not geo) dataframe but I need to also plot the full, smooth, track.

I've tried this:

        layers = [ 
pdk.Layer(
    type = "PathLayer",
    data=tracks,
    get_path="geometry",
    width_scale=20,
    width_min_pixels=5,
    get_width=5,
    get_color=[180, 0, 200, 140],
    pickable=True,
    ),
]
view_state = pdk.ViewState(
    latitude=gdf_polygon.centroid.x,
    longitude=gdf_polygon.centroid.y,
    zoom=6,
    min_zoom=5,
    max_zoom=15,
    pitch=40.5,
    bearing=-27.36)

r = pdk.Deck(layers=[layers], initial_view_state=view_state)
return(r)

Which silently fails. Try as I might, I cannot find a way to convert the LINESTRING Z's (and I can do without the Z component if need be) to an object that pydeck will accept.

Felipe D. · Accepted Answer · 2021-09-27T23:32:28.280

I found a way to extract the info needed from GeoPandas and make it work in pydeck. You just need to apply a function that extracts the coordinates from the shapely geometries as a list. Here is a fully reproducible example:

import shapely
import numpy as np
import pandas as pd
import pydeck as pdk
import geopandas as gpd


linestring_a = shapely.geometry.LineString([[0,1,2],
                                            [3,4,5],
                                            [6,7,8]])

linestring_b = shapely.geometry.LineString([[7,15,1],
                                            [8,14,2],
                                            [9,13,3]])

multilinestring = shapely.geometry.MultiLineString([[[10,11,2],
                                                     [13,14,5],
                                                     [16,17,8]],
                                                    [[19,10,11],
                                                     [12,15,4],
                                                     [10,13,0]]])



gdf = gpd.GeoDataFrame({'id':[1,2,3],
                        'geometry':[linestring_a,
                                    linestring_b,
                                    multilinestring],
                        'color_hex':['#ed1c24',
                                     '#faa61a',
                                     '#ffe800']})

# Function that transforms a hex string into an RGB tuple.
def hex_to_rgb(h):
    h = h.lstrip("#")
    return tuple(int(h[i : i + 2], 16) for i in (0, 2, 4))

# Applying the HEX-to-RGB function above
gdf['color_rgb'] = gdf['color_hex'].apply(hex_to_rgb)

# Function that extracts the 2d list of coordinates from an input geometry
def my_geom_coord_extractor(input_geom):
    if (input_geom is None) or (input_geom is np.nan):
        return []
    else:
        if input_geom.type[:len('multi')].lower() == 'multi':
            full_coord_list = []
            for geom_part in input_geom.geoms:
                geom_part_2d_coords = [[coord[0],coord[1]] for coord in list(geom_part.coords)]
                full_coord_list.append(geom_part_2d_coords)
        else:
            full_coord_list = [[coord[0],coord[1]] for coord in list(input_geom.coords)]
        return full_coord_list

# Applying the coordinate list extractor to the dataframe
gdf['coord_list'] = gdf['geometry'].apply(my_geom_coord_extractor)

gdf_polygon = gdf.unary_union.convex_hull 

# Establishing the default view for the pydeck output
view_state = pdk.ViewState(latitude=gdf_polygon.centroid.coords[0][1], 
                           longitude=gdf_polygon.centroid.coords[0][0], 
                           zoom=4)

# Creating the pydeck layer
layer = pdk.Layer(
    type="PathLayer",
    data=gdf,
    pickable=True,
    get_color='color_rgb',
    width_scale=20,
    width_min_pixels=2,
    get_path="coord_list",
    get_width=5,
)

# Finalizing the pydeck output
r = pdk.Deck(layers=[layer], initial_view_state=view_state, tooltip={"text": "{id}"})
r.to_html("path_layer.html")

Here's the output it yields:

Big caveat

It seems like pydeck isn't able to deal with MultiLineString geometries. Notice how, in the example above, my original dataframe had 3 geometries, but only 2 lines were drawn in the screenshot.

This neatly solves half of the problem, thank you! Unfortunately, pydeck doesn't seem to like LINESTRING any more than it likes LINESTRING Z. — DKovar, Sep 25 '21 at 12:54
There! I've updated the code to make it work with pydeck's PathLayer method. Let me know if you have any issues converting my example above to the specific case you need. — Felipe D., Sep 27 '21 at 18:04
Thank you, very much. I spent the afternoon trying all sorts of conversions and they either failed silently or threw a JSON related parsing error. This works, works well, and is clear. Supposedly PathLayer takes 3D coordinates but I'll worry about that another day. Thank you very much. — DKovar, Sep 27 '21 at 21:45
Creating a polygon from all of the points and then using it's centroid may be faster than the view_state lambdas you use: `gdf_polygon = gdf.unary_union.convex_hull` — DKovar, Sep 27 '21 at 22:24
Well noted! I've updated the code above to incorporate the suggestion =) Thanks for the tip! — Felipe D., Sep 27 '21 at 23:32

Plot LINESTRING Z from GeoDataFrame using pydeck's PathLayer (or TripLayer)

1 Answers1

Big caveat

Linked