Leapfrog the Arm To Measure a Tube Longer than the Arm's Reach

Start a Leapfrog Measurement

Press the Move tab in the guide box at any time during a measurement.

The Steps for Leapfrog

Place the 3 targets or the leapfrog plate as far from the arm as possible in the direction you want to leap.   Press "Leapfrog the Arm" button in the guide window on the left.   Measure the targets with the ball probe or LASER scanner (if using  sphere targets). If using the ball probe, press the green button (FARO) or red button (HEXAGON) to measure each target.   If the Auto Limit Point Count is not active, you will need to press the acquisition button.    Without moving the targets or the tube, move the arm to a new position.   Measure the targets again in the same order as the first measurement.   If the Auto Limit Point Count is not active, you will need to press the acquisition button.   The leap is complete. The Leapfrog windows will disappear. You will see alignment planes on the screen. Continue measuring where you left off before.

The User Interface During Leapfrog

When the leapfrog starts, you will see this new floating window. The top grid represents the before-leap-point locations. The bottom grid represents the after-leap location of the same points.

This is how the point locations will appear.

Example Customer Setup

You can be creative in how you move the arm. Here was one customer's idea that worked well.

The arm was mounted on a rolling cart. The tube was placed on a second table. The leapfrog targets were placed on the same table as the tube.

During the leapfrog movement, only the rolling cart was moved from left to right.

Leapfrog Kit - Magnetic, Plate, Conical Seats, or Spheres

This is the magnetic leapfrog kit that we offer on our store. Each magnet has a conical seat attached to a magnet that can be placed anywhere for leapfrogging
These are the leapfrog plates that we offer on our store. The plates have three numbered conical seats. For conical seats are used for measurement with a ball probe.
These plates have three spheres for use with a LASER scanners.  It's easier to use the ball probe conical set method if you can. However, if you are using a measuring system with no ball probe, then you can use spheres like this to leapfrog.
These leapfrog spheres sit on the table. These are very easy to use for LASER scanning.   They can use magnetic discs attached to the bottom of the red base so that they stay attached to steel tables.  (These don't have the magnets attached.)   We added these spheres an an option in March of 2026.  They are non-porous ceramic alumina with a sphericity (roundness) of 0.0002 inches, or 0.005 mm (5 microns).   They scan very well with the latest blue LASER scanners.

Typical Point Repeatability

This is a report of repeatability for the white ceramic spheres using a HEXAGON 8325 arm with AS1 blue LASER scanner:

This is the same report in millimeters:

The conclusion is that a HEXAGON arm AS1 scanner can repeat a point within 0.002 inches or 57 microns. (For comparison, typical office paper thickness is 0.004 inches or 114 microns.)

This is 0.002 inches in a caliper:

Create Your Own Leapfrog System

You can easily create your own target/monument system. Here are general principles for the positioning of the targets/monuments.

1. Be sure the target positions do not form a straight line.
2. Positions that form the vertices of an equilateral triangle (with all three angles at 60 degrees and all side lengths equal) are the best. However, it is not critical that the triangle formed be exactly equilateral. (It is best that the triangle formed is closer to equilateral than not.)
3. Larger triangles are better than smaller triangles.
4. You can use permanent positions on a plate, or manually place positions on a table in any position. 

About Conical Seats in a Fixed Triangle

The conical seats could be three conical holes drilled into a plate. The vertices at the center of the seats should form a triangle among themselves. (The three holes must not form a line when scribing between the center points of the seats. They need to be offset from each other in order to form a triangle, which will form a plane.)

The shape of the triangle does not matter, as long as the triangle is not close to the shape of a line between the three vertices.

This leapfrog target setup works well.

This leapfrog target setup works well.

This leapfrog target setup will not work. Do not use this linear orientation for the conical seats.

About Spheres in a Triangle Orientation

Use the same positioning principles when using spheres. Place the spheres at the vertices following the same positioning rules. VTube will use the center of the spheres as the points collected.

Video Tutorial - Measure Setup Leapfrog with LASER Scanners

The VTube-LASER Measure Setup/Leapfrog menu contains important settings that allow you to control how Leapfrog takes place. Watch this video for detailed instructions on how to properly set up VTube-LASER Leapfrog for LASER scanners.

SPACE OBJECTS, ASSEMBLY Tubes, Measured Tube are Included in Leapfrogs

As of version 4.5 build 1972 (September 24, 2026), after a leapfrog, the code that re-orients real-time measured data now also moves these objects.

Which objects can move during leapfrogs

• Space Objects - Measured - Untransformed (This can be enabled or disabled.)
• Space Objects - Measured - Transformed  (This can be enabled or disabled. It is disabled by default.)
• Space Objects - Dimensions (This can be enabled or disabled.)
• Real-time data just scanned before the leap (This always happens.)
• The existing measured tube data in the current tube (This always happens)
• Measured tubes in other assembly parts (This can be enabled or disabled.)
   

Why Prismatic Space Objects Move During a Leapfrog

A Leapfrog lets you move the measuring arm to a new location so you can reach parts of a large tube or assembly that are out of range from the first position. Everything the arm measures is recorded relative to where the arm is sitting. When the arm moves, VTube works out exactly how far it moved and turned, then shifts the earlier measurements by the same amount so old and new data line up in one common coordinate system.

Measured Space Objects are recorded the same way as measured tube data, relative to the arm. If they were left behind during a leap, they would still be positioned for the arm's old location, while everything measured afterward would be positioned for the new one. The Space Objects would appear shifted away from the tube, and any dimensions or checks comparing the tube to those objects (such as distances to a mounting bracket or a fixture plane) would be wrong. Moving them with the leap keeps them where they physically belong relative to the tube.

What doesn't need to move during a leapfrog?

Any nominal data for either tubes or space objects comes from the design rather than from the arm, so the arm's position has no effect on them. VTube-LASER does not offer to move them.

Also, the Space Objects set to "Align this Space Object" to the master tube (in the Space Objects menu) will eventually be converted to align with the master coordinate system, so they no longer depend on the arm's position, either, just like the aligned tube.  This is why “Leap Transformed Measured Space Objects” is set to DISABLED by default during the leapfrog process. However, if you want to, you can override this and ENABLE the transformation of these too.

2 - VTube gives you control over which Space Objects are carried along when you perform a Leapfrog move.

Three new options let you decide which data to transform in leapfrogs:

Nominal data is never moved during a leap, regardless of these settings.

Where to find the options

The options appear in two places, and they always stay in sync:

• Measure Setup, Leapfrog settings: three new checkboxes at the bottom of the list. Each has green help text you can click for an explanation of what the option does.
  
   

• Leap Process window: the same three checkboxes, so you can adjust them while leaping. Changing them here requires the same access permission as changing them in Measure Setup.