Reading a GLO Field Note Page: A Primer

The format of an original GLO field note page looks archaic at first. Here's how to decode what you're looking at.

If you've never opened a GLO field note before, the format can look strange. The surveyor wasn't writing prose — they were following a standardized recording format that the General Land Office established in its Instructions to Surveyors, updated periodically from 1815 through the 1940s.

Each page covers one survey line — usually the north or south boundary of a township, or the lines between sections. The surveyor records their starting and ending corners at the top, then lists calls in order as they walk the line.

Each call has two parts: the chain distance, and the observation. "At 40.00 ch., enter heavy timber" means at 40 chains from the starting corner, the surveyor entered a heavily forested area. A chain is 66 feet, so 40 chains is 2,640 feet — exactly half a mile.

Corners are called out at their exact chain distance and documented with witness trees (blazed trees near the corner), the type of corner monument set (stone, post, mound of stones, etc.), and bearing trees. The section corner at the end of a line is typically near 80 chains — one mile — from the previous corner, though the actual recorded distance often varies by a chain or more depending on terrain, the surveyor's equipment, and re-survey corrections.

Our OCR engine is trained to recognize this format and separate the chain-distance calls from the observation text, classify each call by type (terrain, vegetation, water, road, monument, etc.), and link the corner calls to the GCDB database for geolocation.