diff --git a/lookup.py b/lookup.py
index 6c22fd8..5c13411 100755
--- a/lookup.py
+++ b/lookup.py
@@ -14,6 +14,7 @@ else:
 
 # for retreiving geo coordinates from addresses
 geolocator = Nominatim(user_agent="my-mapper")
+# lat: 0=111,1km,1=11km,2=1km… lng: 0=70km,1=7km,2=.7km…
 precision = 2
 # get data from file
 with open( fn, 'r' ) as fp: