Scatter Plot on Projected Pap is not in Correct Location-CodePudding

I have the trajectory of a hurricane. In a "conventional" map CRS, the trajectory of the hurricane is correct

However, when I use a unconventional projection, the location of the hurricane is off. It starts East of North America and then goes West over the land. Why is that?

Here is how I try it

data = {'Lat':{0:12.9,2:12.9,4:13.2,6:13.6,8:13.7,10:13.8,12:14.2,14:14.5,16:14.8,18:16.0,20:17.0,22:17.9,24:18.3,26:18.9,28:19.7,30:20.7,32:22.0,34:23.4,36:24.6,38:25.1,40:25.0,42:24.8,44:24.5,46:24.6,48:24.4,50:24.6,52:25.0,54:25.9,56:26.4,58:27.1,60:28.0,62:28.5,64:29.4,66:30.4,68:31.5,70:32.5,72:33.1,74:33.6,76:33.9,78:34.1,80:34.1,82:34.0,84:33.9,86:33.7,88:33.6,90:33.6,92:33.6,94:33.7,96:34.0,98:35.5,100:38.5,102:39.8,104:42.6},'Long':{0:-18.4,2:-19.4,4:-20.9,6:-21.4,8:-22.7,10:-24.7,12:-25.5,14:-26.7,16:-27.8,18:-30.2,20:-33.2,22:-35.9,24:-38.7,26:-41.0,28:-42.5,30:-43.9,32:-45.7,34:-47.2,36:-48.6,38:-49.8,40:-51.8,42:-53.2,44:-54.3,46:-55.2,48:-56.3,50:-57.7,52:-60.0,54:-62.4,56:-64.6,58:-66.2,60:-67.9,62:-69.5,64:-70.7,66:-71.8,68:-73.2,70:-74.3,72:-75.1,74:-76.0,76:-76.4,78:-77.2,80:-77.9,82:-78.4,84:-78.8,86:-79.3,88:-79.5,90:-79.8,92:-80.1,94:-80.8,96:-81.8,98:-82.1,100:-82.9,102:-80.2,104:-71.9}}

df = pd.DataFrame.from_dict(data)

# Invert longitude for plotting in western Hemisphere
df['Long'] = df['Long'] * -1

newCrs = ccrs.RotatedPole(pole_latitude=37.5, pole_longitude=177.5)
fig = plt.figure(figsize=(20, 10))
ax = plt.subplot(projection = newCrs)
ax.coastlines(resolution = '110m')
ax.scatter(df['Long'], df['Lat'], color = 'red', transform = newCrs)

CodePudding user response：

The issue is that the transform keyword in ax.scatter should be the DATA CRS. So, assuming that your indata is fine with PlateCarree crs:

df = pd.DataFrame(dict(Lat=[i for i in data['Lat'].values()], Long=[i for i in data['Long'].values()]))
 
newCrs = ccrs.RotatedPole(pole_latitude=37.5, pole_longitude=177.5)
dataCrs = ccrs.PlateCarree()

fig = plt.figure(figsize=(20, 10))
ax = plt.axes(projection = newCrs)
ax.set_global()
ax.coastlines()
ax.scatter(df['Long'], df['Lat'], color = 'red', transform = dataCrs)

gives:

Please read

General tips/comments

You should not need to flip the Longitude coordinates at all.
Did you check if there are any issues with Matplotlib/Cartopy?
If you have the Proj4 definition string you do not even need cartopy if using GeoPandas.
You should probably clean up the use of Pandas DataFrame, storing a dictionary in a column of a dataframe is not really recommended, and probably makes your life more difficult.