Display geographical points using geopandas

Question

I want to display points on the map using a shape file as a map and a csv with coordinates. The code works but I don't understand how to show the figure map. My questions are: how to display the points? What is "WnvPresent"? How can i just display the map and the points, not as a split between negative and positive but as a hole? Website from where i downloaded the shp file: https://ec.europa.eu/eurostat/web/gisco/geodata/reference-data/administrative-units-statistical-units/countries Website from where the idea comes from: https://towardsdatascience.com/geopandas-101-plot-any-data-with-a-latitude-and-longitude-on-a-map-98e01944b972

import pandas as pd
import matplotlib.pyplot as plt
import descartes
import geopandas as gpd
from shapely.geometry import Point, Polygon
 %matplotlib inline 
#read map data in form of .shp
street_map = gpd.read_file(r"C:\Users\stetc\Desktop\images/portofolio\ref-countries-2016-01m.shp")
#create the map
fig,ax = plt.subplots(figsize=(15,15))
street_map.plot(ax = ax)
#read given data
df = pd.read.file(r"C:\Users\stetc\Documents\full_dataset.csv")
#the next step is to get the data in the right format. The way we do this is by turning our regular Pandas DataFrame into a geo-DataFrame, which will require us to specify as parameters the original DataFrame, our coordinate reference system (CRS), and the geometry of our new DataFrame. In order to format our geometry appropriately, we will need to convert the longitude and latitude into Points (we imported Point from shapely above), so first let’s read in the training data-set and specify the EPSG:4326 CRS like so
crs = {"init":"epsg:4326"}
#create points using longitude and lat from the data set
geometry = [Point(xy) for xy in zip (df["Longitude"], df["Latitude"])]
#Create a GeoDataFrame 
geo_df =gpd.GeoDataFrame (df, #specify out data
                          crs=crs, # specify the coordinates reference system
                          geometry = geometry #specify the geometry list created
                         )
fig,ax = plt.subplots(figsize = (15,15))
street_map.plot (ax = ax, alpha = 0.4 , color="grey" )
geo_df[geo_df["WnvPresent"]==0].plot(ax=ax,markersize=20, color = "blue", marker="o",label="Neg")
geo_df[geo_df["WnvPresent"]==1].plot(ax=ax,markersize=20, color = "red", marker="o",label="Pos")
plt.legend(prop={"size":15})

martinfleis martinfleis · Accepted Answer · 2019-12-10T10:28:32

WnvPresent is just a column used in the example to plot two different colours (I would do it differently, but that is for another discussion), you can ignore that if your goal is to plot points only.

Try the code below. I have also added zorder to ensure that points are on top of the street_map.

fig, ax = plt.subplots(figsize=(15,15))
street_map.plot(ax=ax, alpha=0.4, color="grey", zorder=1)
geo_df.plot(ax=ax, markersize=20, color="blue", marker="o", zorder=2)

In the first step you create the figure, then you add street_map to ax and then geo_df to the same ax. The last line answers your question "how to display the points?". Keep in mind that both layers has to be in the same CRS (assuming epsg 4326 from your code), otherwise layers won't overlap.

A bit more on plotting is in geopandas docs - https://geopandas.readthedocs.io/en/latest/mapping.html and on CRS here https://geopandas.readthedocs.io/en/latest/projections.html.

Display geographical points using geopandas

1 Answers