PLM индивидуальное измерение не определено

import pandas as pd

df3 = df1[['Lat1', 'Lon1']]
df3['tp1-tp2'] = df1.tp1 - df2.tp2


Out[97]: 
      Lat1      Lon1  tp1-tp2
0  34.4750  349.8350     -1.0
1  34.4769  349.8621     -0.5
2  34.4788  349.8891      0.0
3  34.4807  349.9162     -3.0
4  34.4826  349.9433      0.0
5  34.4845  349.9703      0.0