Check if point in GIS polygon fails to produce correct output

Question

I've tried many, many many, ways to find out if a point is in a GIS polygon based on many great posts, but I can't get any to work properly. Specifically I created a grid of points covering the bounding box of Japan, and now I want to keep only the ones that are actually over Japan.

Here is one way I tried to get a GIS shapefile for Japan:

world = gp.read_file(gp.datasets.get_path('naturalearth_lowres'))
JapanShapes =  world[world.name == "Japan"]
geoJapanShapes = gp.GeoDataFrame(JapanShapes2)
geoJapanShape = geoJapanShapes['geometry'].unary_union

I have millions of point data in a geodataframe, but here's just one point (Tokyo station).

allCoords = pd.DataFrame([[35.6812,139.7671]], columns=["lat","lon"])
allCoords['geometry'] = allCoords.apply(lambda row: "POINT ("+str(row.lat)+" "+str(row.lon)+")", axis=1)
allCoords = gp.GeoDataFrame(allCoords)
allCoords['geometry'] = allCoords['geometry'].apply(wkt.loads)

Now, if test whether Tokyo station is in Japan:

print(allCoords['geometry'][0].within(geoJapanShape))
>>>> False

However, the last time I checked Tokyo station was within Japan. And if I do:

coordsWithinJapan = allCoords[allCoords.apply(lambda row: row['geometry'].within(geoJapanShapes), axis=1)]
>>>> AttributeError: ("'GeoDataFrame' object has no attribute '_geom'", 'occurred at index 0')

Based on several other posts I also tried:

from geopandas.tools import sjoin
gridWithinJapan = sjoin(geoHexData, geoJapanShapes, how='left', op='within')

Which just returns every point in the original data. If I try with the inner option I instead get an empty dataframe.

So both methods (kinda) run on my data, but neither method is working to accurately report whether a point is within the boundary. Other versions gave me crs errors, but I don't how to deal with that considering my points are hand-made. Another had a problem because maybe/apparently that shapefile is a multipolygon, which it couldn't handle. No matter what I try, I seem to be doing something wrong, but I can't find the error.

How do I actually determine whether my points are in my shape?

Answer 1

The Geopandas docs mention coordinates should be created as a tuple of Longitude and Latitude (not latitude and longitude). Switching your lat/lon will give you the result you are expecting.

I was not able to run your code completely because I'm not sure what wkt.loads is, but the following is similar and returns True as expected:

import pandas as pd
import geopandas as gp
from shapely.geometry import Point

world = gp.read_file(gp.datasets.get_path('naturalearth_lowres'))
JapanShapes =  world[world.name == "Japan"]
geoJapanShapes = gp.GeoDataFrame(JapanShapes)
geoJapanShape = geoJapanShapes['geometry'].unary_union

TokyoStation = Point(139.7671, 35.6812)

print(geoJapanShape.intersects(TokyoStation))
True
print(TokyoStation.intersects(geoJapanShape))
True