FMB sketch calculation online — enter G-line notation and bend cutting points with offsets to calculate distances along the line, to endpoints, or diagonally between bends. Pair with the links to feet converter or RSR & FMB area error adjuster.
How to useHow It Works
1. Enter G-Line
Provide the G-Line notation (e.g. AB) and the total distance along the line.
2. Add bends
For each bend, enter the cutting point distance, offset, and direction (right or left). At least one bend is required.
3. Calculate & visualize
Choose the distance type, click calculate, then export results or visualize the bend geometry on a diagram.
How to Calculate FMB Sketch Measurements
G-Line and cutting points
Every FMB sketch is drawn along a G-line (baseline). Each bend is marked at a cutting point (chainage along the G-line) with a perpendicular offset to the left or right of the line.
Distance formula
For a bend at chainage x with offset y, place it at coordinates (x, y) on the G-line. Distance between two bends uses the Pythagorean theorem:
d = √[(x₂ − x₁)² + (y₂ − y₁)²]
Start-to-bend and bend-to-end distances use the same formula from the G-line endpoint (0, 0) or end point.
FMB area calculation
This tool computes linear distances along bends. For total plot area from an FMB sketch, triangulate the boundary polygon or use the land area calculator. When RSR area differs from plotted FMB area, use the RSR & FMB area error adjuster.
About this tool
- FMB sketch G-line notation
- Bend cutting points and offsets
- Distance between bends
- Visual bend diagram
- Export-friendly results
What G-line bends mean
On an FMB sketch, a G-line is the main chain line between two survey points. Boundary bends are recorded as chainage (cutting point) plus left or right offset from that line. This calculator places those bends in plane geometry and computes distances between them.
How to enter data
Type the G-line label (for example AB), total G-line length, then each bend’s cutting point, offset distance, and side. Calculate start-to-bend, bend-to-bend, and bend-to-end distances as needed for recovery or area prep.
Related area work
This tool solves linear bend geometry. For area differences between registered and plotted extents use the RSR and FMB area error adjuster. Confirm stones on ground before treating computed distances as final.
Frequently Asked Questions
What is an FMB sketch calculator online?
An FMB sketch calculator online computes distances along a G-line between bend cutting points using offsets from your Field Measurement Book sketch — without manual trigonometry.
How do I calculate FMB sketch measurements?
Enter G-line notation (e.g. AB), total G-line distance, then each bend's cutting point, offset distance, and left/right direction. Click Calculate to get point-to-point distances.
What is the FMB calculation formula used here?
Distances use coordinate geometry on the G-line: each bend is placed at its chainage with perpendicular offset, then Euclidean distance is computed between selected bends (start-to-bend, bend-to-end, or diagonal).
Can this tool calculate FMB area?
This calculator focuses on linear distances and bends. For area between RSR and plotted FMB area, use the RSR and FMB Area Error Adjuster tool.
Is FMB sketch calculation online free?
Yes. Free for AP village and mandal surveyors; runs entirely in your browser.
Corrections & questions
These guides are maintained for practising AP surveyors. If a step is outdated or wrong, tell us — we prioritise field corrections.
Comments are not stored on this page. The report form attaches this URL automatically.