Python Bokeh – Plotting glyphs over a Google Map

Bokeh is a Python interactive data visualization. It renders its plots using HTML and JavaScript. It targets modern web browsers for presentation providing elegant, concise construction of novel graphics with high-performance interactivity.

Bokeh can be used to plot glyphs over a Google map. A glyph is a hieroglyphic character or a symbol. To use Google maps in Bokeh, we will use the gmap() function of the plotting class.

gmap()

Syntax : gmap(parameters)
Parameters :

  • google_api_key : key of the Google API
  • map_options : GMapOptions i.e. the configuration specific to the Google map
  • active_drag : drag tool that is to be initially active
  • active_inspect : inspect tool that is to be initially active
  • active_scroll : scroll tool that is to be initially active
  • active_tap : tap tool that is to be initially active
  • title : title of the Google map
  • tools : tools the plot should start with
  • x_axis_label : label for the x-axis
  • x_axis_location : location of the x-axis
  • x_minor_ticks : number of minor ticks between adjacent x-axis major ticks
  • y_axis_label : label for the y-axis
  • y_axis_location : location of the y-axis
  • y_minor_ticks : number of minor ticks between adjacent y-axis major ticks

Returns : an object of the class GMap

Now let us see how to configure the Google map using the GMapOptions() function :



GMapOptions()

Syntax : GMapOptions(parameters)
Parameters :

  • lat : latitude where the Google map is to be centered
  • lng : longitude where the Google map is to be centered
  • map_type : type of map to be used for the plot, here are the map types available :
    • hybrid
    • roadmap
    • satellite
    • terrain
  • name : name for the Google map
  • scale_control : whether the Google map should display its distance scale control
  • styles : style of map to be used for the plot
  • subscribed_events : list of events that are subscribed to by Python callbacks
  • tags : tags associated with the Google map model
  • tilt : tilting the angle of the map
  • zoom : initial zoom level of the Google map
  • apply_theme : theme of the model

Returns : an object of the class GMapOptions

Let us see how to plot glyphs over a Google Map :

  1. Import the required libraries and modules :
    • gmap from bokeh.plotting
    • ColumnDataSource and GMapOptions from bokeh.models
    • output_file and show from bokeh.io
  2. Create a file to store our model using output_file().
  3. Configure the Google map using GMapOptions().
  4. Generate a GoogleMap object using gmap().
  5. Determine the coordinates of the glyphs using ColumnDataSource().
  6. Generate the glyphs on the created Google map object.
  7. Display the Google map using show().
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# importing the required modules
from bokeh.plotting import gmap
from bokeh.models import ColumnDataSource, GMapOptions
from bokeh.io import output_file, show
  
# file to save the model
output_file("gfg.html")
  
# configuring the Google map
lat = 28.7041
lng = 77.1025
map_type = "hybrid"
zoom = 11
google_map_options = GMapOptions(lat = lat,
                                 lng = lng,
                                 map_type = map_type,
                                 zoom = zoom)
  
# generating the Google map
google_api_key = ""
title = "Delhi"
google_map = gmap(google_api_key,
                  google_map_options,
                  title = title)
  
# the coordinates of the glyphs
source = ColumnDataSource(
    data = dict(lat = [28.6, 28.65, 28.7, 28.75, 28.8, 28.85],
                lon = [76.95, 77, 77.05, 77.1, 77.15, 77.25]))
  
# generating the glyphs on the Google map
x = "lon"
y = "lat"
size = 20
fill_color = "red"
fill_alpha = 1
google_map.square(x = x,
                  y = y,
                  size = size,
                  fill_color = fill_color,
                  fill_alpha = fill_alpha,
                  source = source)
  
# displaying the model
show(google_map)

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Output :

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