---
title: "FF/FL Define sample lines"
slug: "cyclone-3dr-fffl-definesamplelinesc"
updated: 2026-09-07T11:51:38Z
published: 2026-09-07T11:51:38Z
canonical: "rcdocs.leica-geosystems.com/cyclone-3dr-fffl-definesamplelinesc"
---

> ## Documentation Index
> Fetch the complete documentation index at: https://rcdocs.leica-geosystems.com/llms.txt
> Use this file to discover all available pages before exploring further.

# FF/FL Define sample lines

![WorkflowFFFL.svg](https://cdn.document360.io/820e11db-8ed5-45ae-ac86-f6b77dcb2aa7/Images/Documentation/WorkflowFFFL.svg)

This step helps to arrange the sample lines inside each test section (according to the standard).

For each test section:

1. Choose the appropriate pattern among **Parallel and perpendicular** and **45 degrees**.
2. Define the **Number of sample lines** (perpendicular to the main direction or the 45 degrees direction).
3. If the **Compute** button is greyed out, the computation would fail: refer to the notes below.
4. Otherwise, click **Compute**: a levelness colormap is computed and you can **Edit color**. In case of failure, refer to the notes below.

> [!WARNING]
> ### Notes
> 
> A failure means the computation can't be made according to the standard:
> 
> - increase the number of sample lines (double click the actual number). The FL computation requires a higher cumulative length than FF computation.
> - rearrange the sample lines in orange (sample line too close to another one) and red (sample line crossing a hole in your cloud):
>   - automatically:
>     - change the pattern mode.
>     - change the pattern main direction (only in 45 degrees mode).
>   - or manually:
>     - select one and give it a new position.
>     - select one and shorten it using **CTRL + MOUSE WHEEL** (only in 45 degrees mode).