FMB Full Form & How to Read an FMB Sketch
FMB = Field Measurement Book — the official sketch of one survey number. Learn to read the F-line, G-line, measurement ladder and its units (metres, chains, links), step by step.
FMB stands for Field Measurement Book. In Tamil Nadu land records, the FMB is the Survey Department's book of scaled sketches — one page for every survey number in a village — maintained at the taluk office. The 'FMB sketch' you download is one page of that book. It can look like a maze of lines and figures, but once you know what each part means, it reads clearly.
FMB full form and meaning in land records
Field Measurement Book — the FMB full form — means exactly what it says: a book of field measurements. For each survey number it records the shape of the field, the length of every boundary, and the internal measurements a surveyor needs to re-fix those boundaries on the ground. When people say 'FMB map' or 'FMB sketch', they mean this drawing. It is not proof of ownership (that is the patta's job); it is the measurement record that shows where the boundaries of the land lie.
The G-line and the F-line
The G-line (Gramam line) is the village boundary — the outer edge of the village. The F-line (field line) is the boundary of an individual field or survey number — the line all the ladder measurements hang off. There is one G-line around the whole village but many F-lines, one around each field. Together they tell you where your plot sits and where the village ends. For a deeper walkthrough of the village boundary, see the related G-line guide linked below.
The measurement 'ladder'
Down the side of the FMB sketch you'll see a table of measurements — often called the ladder. It lists the distances along each boundary so the plot can be reconstructed exactly on the ground.
What measurement unit does an FMB use?
It depends on when the village was surveyed. Modern and resurveyed FMB sketches record distances in metres — that's what you'll see on most sketches downloaded from the e-Services portal today. Older FMBs from the original surveys used chains and links: a Gunter's chain is 66 feet long and divided into 100 links, so one link is roughly 0.2 metres. Areas follow the same split — hectares and ares on metric records, acres and cents on older ones.
- 1 chain = 100 links = 66 feet ≈ 20.12 metres
- 1 link ≈ 0.66 feet ≈ 0.2 metres
- 1 acre = 100 cents ≈ 0.4047 hectares
- 1 cent ≈ 435.6 sq ft ≈ 40.47 sq m
- 1 hectare = 2.471 acres
Subdivision numbers inside the field
Inside the field boundary you'll see the survey number and any subdivision numbers (like 12/1, 12/2). Each subdivision is a separate parcel with its own owner in the A-Register, even though they share one survey number.
Why the ground may differ from the FMB
Small differences between the FMB and the physical measurements are normal. Surveys allow for an error margin, and old measurements were taken with chains and theodolites. If the difference is large, that's when you ask for a fresh survey.
Frequently asked questions
What is the full form of FMB?+
FMB stands for Field Measurement Book. It is the Survey Department's book of scaled sketches, one per survey number, recording the boundary measurements of every field in a village. The FMB sketch for your land is one page of this book.
What is the measurement unit in an FMB sketch?+
Modern and resurveyed Tamil Nadu FMB sketches use metres. Older FMBs from the original surveys used chains and links — one Gunter's chain is 66 feet divided into 100 links, so one link is about 0.2 metres. Areas appear as hectares and ares on metric records, and acres and cents on older ones.
What is the F-line in an FMB sketch?+
The F-line (field line) is the boundary of an individual field or survey number inside the village — the line the ladder measurements are tied to. Don't confuse it with the G-line, which is the single outer boundary of the whole village.
What is the G-line in an FMB sketch?+
The G-line (Gramam line) is the village boundary — the outermost line on the sketch that separates one revenue village from the next. It is different from the F-line, which is the boundary of an individual field or survey number inside the village.
What does the measurement ladder on the side show?+
The ladder is a table of distances measured along each boundary of the field. Surveyors use it to plot the exact shape of the plot on the ground, so it's the part you check when verifying an area.
Why doesn't the FMB match my ground measurement exactly?+
A small error margin is normal because older surveys used chains and theodolites. Only a large mismatch is a reason to apply for a fresh survey through the taluk survey office.
Can I download an FMB sketch and combine several into one map?+
Yes. You can download the FMB sketch for each survey number free from the Tamil Nadu e-Services portal (eservices.tn.gov.in). To see several adjoining survey numbers together, join the downloaded sheets into one continuous Combined FMB Sketch with Village Map Joiner — free to assemble and preview in your browser.
Can a photo or image be used as an FMB sketch?+
An FMB sketch is the Survey Department's official scaled drawing for a survey number. A clear scan or downloaded image of that official sketch is a valid copy, but an ordinary photo of the land is not an FMB. Always use the sketch issued for the survey number from the e-Services portal or the taluk survey office.