Pyproj
lastmod 2024-04-30created 2019-11-2816 edits
Python interface to PROJ (cartographic projections and coordinate transformations library)
Initializing CRS
The CRS class can be initialized in many different ways. Here are some examples of initialization.
from pyproj import CRS
crs = CRS.from_epsg(4326)
crs = CRS.from_string("epsg:4326")
crs = CRS.from_proj4("+proj=latlon")
crs = CRS.from_user_input(4326)
Converting projected coordinates
- Converting projected coordinates to lat/lon using Python?
- Converting EPSG:2263 to WGS84 using Python Pyproj
Using transform:
from pyproj import Proj, transform
inProj = Proj(init='epsg:3857')
outProj = Proj(init='epsg:4326')
x1,y1 = -11705274.6374,4826473.6922
x2,y2 = transform(inProj,outProj,x1,y1)
print x2,y2
Using Proj4 arguments:
import pyproj
p = pyproj.Proj("+proj=merc +lon_0=0 +k=1 +x_0=0 +y_0=0 +a=6378137 +b=6378137 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs")
lon, lat = p(x, y, inverse=True)
print lat, lon
Calculating the distance between two coordinates
You can use the library pyproj, that allows you to change the coordinate system. I use EPSG3035 that is convenient for Europe, but depending on where your points are you might have to use a different one.
import pyproj
import numpy as np
lon1 = 2
lat1 = 48
lon2 = 2
lat2 = 49
x1, y1 = pyproj.transform(wgs84, epsg3035, lon1, lat1)
print(x1, y1)
x2, y2 = pyproj.transform(wgs84, epsg3035, lon2, lat2)
print(x2, y2)
# a Pythagore's theorem is sufficient to compute an approximate distance
distance_m = np.sqrt((x2-x1)**2 + (y2-y1)**2)
print(distance_m)
The error will be typically of a few percents for points in Europe, depending on where they are and how far they are. Have a nice day !
Using Geod
import pyproj
geod = pyproj.Geod(ellps='WGS84')
for city, coord in cities.items():
lat0, lon0 = london_coord
lat1, lon1 = coord
azimuth1, azimuth2, distance = geod.inv(lon0, lat0, lon1, lat1)
print(city, distance)
print(' azimuth', azimuth1, azimuth2)
Other methods
- More accurate calculation methods: Calculate distance, bearing and more between Latitude/Longitude points
- For the method using Geopy, see that page.
Geod class
How to get the position after moving a given distance:
- Get the azimuths (1->2, 2->1) and distance from two longitude/latitude pairs.
- The resulting position after moving
meterdistance from a given position (longitude/latitude) at a given azimuth.
import pyproj
meter = 30
lons1 = 127.30594507347541
lats1 = 36.63872883265555
lons2 = 127.306055839949
lats2 = 36.638730247186125
geodetic = pyproj.geod.Geod(ellps='WGS84')
az12, az21, dist = geodetic.inv(lons1, lats1, lons2, lats2) # 1
endlon, endlat, backaz = geodetic.fwd(lons1, lats1, az12, meter) # 2