Plumb-bob: a handy tool to measure the world around you

The “Measurement 3D – Plumb-bob” app is a handy application which makes use of the phone internal sensor and camera to display a virtual plumb-bob. With this application you can check that lines are vertical or horizontal, verify proportions, or check that an object is properly centered.
This tool comes with a snapshot feature. In this mode, it is no longer required to hold the device in the air. Therefore, it is easier to precisely adjust the position of the plumb-bob in the picture and you can also rotate the frame to align it with a wall that is not directly facing you.
When you save this snapshot, you do not simply save an image. You record a complete 3D scene, and you have the ability to later measure any part of it! This is useful when you go shopping and wonder if a piece of furniture can fit in your living room. Or if you plan to move and wonder, for example, if your wardrobe will fit in the truck.

Extra features in the paid version

A paid version of this 3D measurement app contains extra features. This version is called “Plumb-bob+” and does not contain ads. In addition, here is a list of its characteristics:

• no limit to the number of 3D scenes saved in library,
• increase of the number of rows and columns of the grid up to 20,
• plumb bob in 3D shape (box or cylinder),
• estimations of surfaces and volumes,
• higher sensor refresh rate which allows a smoother animation. You can adjust the rate with the preference menu,
• possibility to customize colors and font size.

Tutorial

The app contains an inline tutorial that will guide you the first time you use it. It shows it by default only once. It you want to see it again, you can reactivate it from the preferences menu.

Different types of frame for different use cases

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A reference height to get accurate measurements

To estimate distances, the application relies on the camera height. Because the application can not guess this height, you must manually enter it. There are buttons on the right hand side for that. There are 2 ways to adjust the camera height:

• you can set the height directly (measure the distance of the camera from the ground and try to keep it at the same height during all your measurements),
• or, if you know precisely the measure of an horizontal or vertical segment, make sure the virtual frame is aligned to it, and fill the corresponding field (the camera height will be automatically computed from this measurement).

Note that you adjust only one distance at a time. The application deduce the 2 others from the first one.

Types of 3D measurement made by the app

The app shows the distance estimations in a black rectangle that you can move around with your finger. Here is the explanation of the meaning of each value:

• H: the camera height (see the calibration section to learn how to adjust it)
• D: the estimated distance from your feet to the plumb-bob bottom (that is supposed to touch the ground)
• w: the estimated frame width
• h: the estimated frame height
• d: the estimated frame depth when in 3D
• z/x: the height/width ratio
• a: the estimated angle value
• S: the estimated 2D frame surface
• V: the estimated 3D frame volume

3D measuremnt app calibration

Sometimes, the internal sensor settings of the device are not properly calibrated. Therefore, the app contains a calibration page (which opens with the calibration button of the main page). This page allows to adjust 2 parameters that are necessary to perform accurate measurements: the camera angles of view, and the internal accelerator sensor calibration.

Camera angles of view: your phone system normally reports this information. However, some manufacturers do not provide a valid value. In that case you must measure those angles manually and fill the corresponding fields. If the invalid values are not corrected, the plumb-bob line will still be displayed vertically, but the frame sides will not.

Internal sensor calibration: because the device internal sensor is not always accurate, this tool comes with a dedicated calibration feature

Install the “Measurement 3D – Plumb-bob” app

Download “Measurement 3D – Plumb-bob” app now and start measuring the world around you!

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