Python Bokeh – Plotting glyphs over a Google Map

Last Updated : 03 Jul, 2020

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 :

Import the required libraries and modules :
- gmap from bokeh.plotting
- ColumnDataSource and GMapOptions from bokeh.models
- output_file and show from bokeh.io
Create a file to store our model using output_file().
Configure the Google map using GMapOptions().
Generate a GoogleMap object using gmap().
Determine the coordinates of the glyphs using ColumnDataSource().
Generate the glyphs on the created Google map object.
Display the Google map using show().

# 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) 