Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_name_31 (geohash_length INTEGER, lng_error VARCHAR, lng_bits VARCHAR)

### Question ###
What is the highest geohash length when there is a ng error of ±0.00017, and a lng bits smaller than 20?

### Accurate SQL ###

SELECT MAX(geohash_length) FROM table_name_31 WHERE lng_error = "±0.00017" AND lng_bits < 20