There are new innovations being made in technology all the time. Some are outlandish, but some become a vital part of our lives. I believe that the laser measuring tool is one of those devices that will become (if it hasn’t already) a vital part of our lives, especially for those who are involved in construction. Bosch makes several versions of laser measuring tools and the Bosch GLM 50 C is a mid-range unit. This particular device is small and lightweight; measures distances of up to 165 feet; measures length, area, volume, indirect length, stake-out length, and angle; is accurate to 1⁄16 inch and 0.2°; and has Bluetooth functionality allowing you to connect to the Bosch app to save all your data. This device is very functional, easy to use, and accurate. However, the accuracy of some measurements was less than ideal primarily due to the measurement technique or the inability to keep the GLM perfectly still while taking a measurement. The GLM can be used with or without the app. However, the memory of the GLM is limited to only 30 measurements, and these measurements are not time stamped and cannot be renamed unless you are using the tool with the app. My husband, Rob, (a mechanical engineer) tested this device and is the person who wrote the rest of this review. This is a very detailed and lengthy review, but it has a lot of section headings for readers to skip or peruse as desired.
- Bosch Laser Measuring Tool (GLM 50 C)
- Nylon Carrying Case
- Carrying Strap
- 2 – 1.5V AAA batteries
- Yellow Target Cards
- Quick Start Guides for the tool and app
- User Manual
- Product Registration Card
- Linear Range: 6 inches to 165 ft
- Linear Accuracy: +/- 1/16″
- Angular Range: 0 – 360°
- Angular Accuracy: +/- 0.2°
- Weight: 0.22 lbs
- Dimensions: 4.2 x 1.8 x 0.9 inches
- Battery: 2 x 1.5V AAA
- Battery Life: 10,000 individual measurements (Bluetooth disabled)
- Battery Life: 2.5 h real-time measurements (Bluetooth disabled)
- Operating Temperature: 14 – 113 °F
- Max Relative Humidity: 90%
- Laser Class: 2
- Laser Type: 635 nm, < 1 mW
- Protection: IP 54 (dust and splash proof, battery compartment not included)
- Bluetooth 4.0
- 1/4″ thread tripod mount
Design & Build Quality
The Bosch Laser Measuring Tool model GLM 50 C is made of lightweight plastic and has a rubberized button control panel.
The back of the device has an easy-to-remove panel to insert the two AAA batteries that are provided and a threaded attachment point for a tripod mount.
The top of the device contains the diode laser (on the right) and the laser sensor (on the left).
Each side of the device has a black rubber area to help with grip. The sides of the GLM 50 C are square to allow placing the device on a surface or against an object for accurate measurements. As stated in the specifications, the unit is rated for Ingress Protection (IP) factor 54 for dust and splash protection, but this protection does not apply to the battery compartment. This is approximately equivalent to the US NEMA 3 standard.
Device Settings and Display
The GLM is controlled with seven buttons on the front face of the unit:
- Measure Button (Red button with the triangle): This button is used to either activate the laser, or if the laser is on it will take the measurement.
- Plus and Minus Buttons (+ / -): These buttons are used to select the mode of operation or select different settings as required.
- Function Button (Func): This button will bring up a selection of operating modes or settings, and is used in conjunction with the Plus and Minus buttons to make selections as required.
- Measuring Reference Button (Device with arrow): This is used to adjust the measurement reference point.
- Clear / On / Off Button (C and red circle): Used to turn the device on or off or to clear the memory.
- Bluetooth Button: Used to pair the GLM to an Android or iOS device using Bluetooth.
Device Settings: The measurement mode is chosen by pressing the Function button (more details below on measurement modes). The GLM settings are changed by pressing and holding the Function button. These settings allow you to change the units (options are decimal feet, decimal meters, decimal centimeters, fractional inches, and fractional feet and inches). In addition, the sound can be silenced, rotation of the screen turned on or off, the text size changed to small or large, the bubble level display on the main screen turned on or off, and a unit self-calibration can be performed. The reference point is chosen with the Measuring Reference Button on the lower right-hand side of the device control panel. You can take measurements with respect to the end of the device, the front of the device, or the middle of the device which corresponds to the tripod attachment point. An icon that represents the selected reference point is shown on the screen. When powered on, the unit defaults to the mode where the reference point is the end of the device as shown in the picture above (the top center icon on the display).
Display: The GLM display is backlit and very bright and easy to read, even outdoors in sunlight. It has multiple colors and will automatically rotate as you rotate the device if that setting is turned on. The icon representing the measurement mode is shown in the lower left-hand corner of the display, and a battery indicator is shown in the upper right-hand corner of the display. In the picture above, the device is set to small text size with the reference point chosen to be at the end of the device. The reference point selection is shown at the top of the display and also shows a flashing red indicator on the screen when the laser beam is on. The text size setting only affects the display when in Real Time mode, with the small text size option shown above. For this mode only, the large text size option will significantly increase the size of the measurement display, but the display will not show the min and max values, the mode icon, the bubble level, or the reference point. For all other modes of operation, the display uses small text size and selecting large text size has no effect on the display. Also, if the feature is activated, as shown above, a bubble level is displayed on the left side of the display to allow the user to ensure that the device is level when taking a measurement.
The GLM 50 C is packed with features and provides an enormous amount of measurement flexibility. We tested each of the eight measurement modes (starting clockwise from the top in the picture above); real time, area, volume, indirect, wall area, stake out, memory (not a measurement mode), level, and length. The device is fully functional even without the app, but connecting to your device provides even more flexibility for downloading data and even controlling the GLM from your device. The desired mode is chosen by pressing the Function button on the device and then using the Plus or Minus buttons to select the mode, and then pressing the Function button again.
Each mode is indicated with an icon as shown in the picture above, and on this mode selection page the highlighted icon is identified by a label located at the top of the display so you can tell what it is. The icon for the mode that you have selected is displayed on the screen when using the device to measure. Also, the icon aids in taking measurements by changing how it is displayed on the screen as the measurement is taken with a flashing red indicator (used to show which measurement is being taken), and in some cases the icon will be filled in with green when the measurements have been completed and the result is displayed (for area and volume calculations that require multiple measurements).
Description of the Eight Measurement Modes:
Real Time: (Dashed arrow between two vertical lines icon) – When you first turn the unit on it defaults to real time mode where it displays the real-time distance, adjusting the value approximately every 0.5 seconds. Pressing the Measure button will lock in the measurement and turn off the laser. Pushing the button again will clear the measurement and turn the laser back on. This mode is useful for a quick measurement, but the real time feature also allows you to move an object in real time to set a required distance or position (instead of adjusting then measuring repeatedly). This mode will also display the minimum and maximum lengths that the unit has read while the laser was on. The max and min values are reset when you power the unit off.
Length: (Solid line between two vertical lines icon) – The length mode requires the user to push the Measure button to turn the laser on, and records the measurement after the second press of the button. This setting will not give the real time measurement nor does it provide max or min values, but it will display the previous two measurements taken. Otherwise, this mode is the same as Real Time.
Area: (Square icon) – This mode is useful for calculating the square footage of a room or any other area, as long as it is in the shape of a square or rectangle. Pushing the Measure button activates the laser and allows measurement of the length. Pushing the Measure button will lock in the first measurement and readies the unit to take the second (width) measurement. Once the second measurement is taken, both length measurements are displayed on the screen and the unit calculates the area and displays that as well.
Wall Area: (Two sides of a cube icon) – This is a variation on the Area mode that is used when it is desired to calculate the total area of multiple walls with the same height, which would be useful for a painter, for instance. As with the Area mode, you push the Measure button to activate the laser then push it again to take the height measurement first. Then subsequent wall length measurements can be taken with subsequent pushes of the Measure button. The last length measurement taken is always displayed, as is the total sum of all lengths and the total wall area. As many length measurements that are necessary can be taken and the total wall area will be calculated. Since only one height measurement is taken, this mode will only work for walls that are the same height.
Volume: (Cube icon) – This mode will allow measurement of the volume of a room that is square or rectangle shaped with a flat ceiling of uniform height, and works in a similar fashion as the Area mode. The laser is activated by pushing the Measure button, and with each subsequent push of the button the length is taken, then the width, and finally the height, at which time the volume is calculated. The volume and the three length measurements are all displayed.
Indirect: (Right triangle icon) – This mode allows measurement of a length or height indirectly. This is useful if there are obstructions that would prevent measurement using the Length mode, or if access to one or both ends is difficult (like the exterior wall to a multi-story house, for instance). There are three types of measurements that can be taken; indirect height, indirect length, or double height. For an indirect height measurement, the GLM is placed on the surface that represents the base of the height measurement, such as the floor for measuring the height of a wall. The Measure button is pressed to activate the laser, and the device should be rotated upwards until the laser beam is located at the desired location. Pressing the Measure button will lock in the measurement and the unit will calculate the height and will also show the measured distance from the unit (the hypotenuse of the triangle) and the angle. The unit is using the Pythagorean Theorem to calculate the height of a right triangle. The indirect length measurement is similar, except that the GLM calculates the horizontal distance between the unit and the wall that the beam has landed on instead of the height of the laser beam on the wall. The double height measurement would be used to determine the height in a case where the device can’t be placed at the base of the wall and is instead mounted on a tripod. The first measurement is to the bottom and the second is to the top, and the device is essentially doing two indirect height calculations and adding the heights together. These measurements can be used for a variety of situations, but the accuracy is dependent upon steady placement of the unit. Also, for the double height measurement, the unit cannot be shifted at all between the two measurements; it should be rotated only. A sturdy tripod is highly recommended for this type of measurement to ensure accuracy.
Stake Out: (Vertical dashed arrow and vertical solid line with tic marks icon) – This mode allows repeated markings of a predefined length, which would be useful for marking locations for wall studs 16″ apart, for example. Once the mode is activated, the Function, Plus, and Minus buttons are used to set the desired stake-out spacing. Then once the Measure button is pressed, a moving scale is displayed on the device. As the device is moved (horizontally along the wall, for instance) the device will display the actual distance from a set point and will emit a beep and show an indicator each time the specified spacing has been reached. Arrows show the direction of the next measurement and the number of measurements relative to the starting point.
Level: (Bubble level icon) – This mode provides angular measurement in two different ways and does not use the laser. When placed flat on a surface, a two-dimensional spirit level (bubble indicator) will be shown that indicates how level the surface is within 3° based on the location of the bubble (it does not give a numerical angle measurement). Pressing the Measure button will lock in the measurement. The indicator will be colored red if the surface is sloped greater than 3°. This mode will also measure one-dimensional inclination in degrees when the GLM is placed on its side. As with the spirit level, pressing the Measure button will lock in the reading. The mode icon and reference point indicators are not shown on the display.
Memory: (Floppy disk icon) – Also from the function screen is an option to view the device memory. The last 30 measurements taken can be reviewed starting with the most recent. The type of measurement and the measurement value is displayed, as well as all individual measurements used for a calculated result (including each individual length for the area and volume measurements and the distance and angles for the indirect measurements).
Buttons: I noticed that it took a little more force to push the buttons than I would have preferred thus increasing the potential for the inaccuracy of the measurement. In most cases, the act of pushing the Measure button to take the measurement would result in some movement of the GLM unless it was sitting directly on the floor. If the end of the GLM was placed against a wall, for instance, it was nearly impossible to push the Measure button without some movement of the laser. For most measurements, this probably has very little effect on the result. However, when trying to do an indirect measurement with the GLM rotated and the laser positioned at the desired end point for a height measurement, it was not possible to hold the unit steady and push the button. Thus achieving a highly accurate indirect height measurement is a challenge. I used a standard tripod for a double length indirect measurement of a 10 ft high wall, and the measurement was off by about 3 inches. This is primarily because the laser was moving when I pushed the Measure button and the entire tripod would shift slightly when trying to rotate the GLM. For this reason, using the app to control the device is preferred (see below for details).
Device memory: Also, the memory will only hold the last 30 measurements which is probably not enough for most major projects. This isn’t much of an issue if you are using the device to take a measurement here or there around the house. However, since this is intended to be a tool for professionals, more memory would have been preferred. One vital feature lacking on the GLM is a time stamp of the measurement or any way to uniquely identify what the measurement was for. This means that the professional user working on a project will either need to manually record the measurements taken, or connect the device to the app.
Use with the Bosch App / Bluetooth Connectivity
App Installation: To get additional functionality out of the GLM 50 C, it can be connected to the Bosch app. There are numerous Bosch apps, so to download the right app, you’ll need to search for the “GLM measure&document” app which is available for Android and iOS. I installed the app on an HTC One M9, Nexus 6, and iPod Touch 5G. Upon opening the app, you are notified that the default measurements are in feet/fractional inches and degrees but this can be changed in the settings.
Pairing: To pair the GLM to your Bluetooth device, you must first have the app installed and running, and have Bluetooth on your device turned on. Next, turn on the GLM and press the Bluetooth button. Since the Bluetooth option defaults to being disabled when the GLM is powered on, the Bluetooth button must be pressed again to turn this on. Then the app will show “Connected to Bosch GLM50C x1234”, where instead of “1234” it will be the last four numbers of the GLM serial number.
Bluetooth Range: Tests of the Bluetooth range were fairly impressive. With the GLM located in a corner room of our house, I was able to maintain connectivity to it using my HTC One M9 phone while walking into all the other rooms of our house, even when I placed myself between my phone and the GLM. To test the maximum Bluetooth range, I set the GLM on a tripod in my yard. While holding a target card (included with the device) and my phone, I walked away from the unit. I stopped occasionally to trigger a length measurement to the target using my phone. I was able to control the GLM from my phone and take measurements up to 100 feet away (unobstructed) indicating successful Bluetooth connectivity. Beyond that distance, the connection became a bit sporadic. It was obvious when the GLM was no longer connected to my phone because the app indicates “No Device Connected” and the laser beam symbol in the app changes from red to gray. I also noticed that over 100 feet, sometimes it would not register the measurement on my phone, and it took several tries to get a measurement value. However, with some persistence, I was able to record a length of 125 feet using my phone to control the GLM. Also, if the Bluetooth connection is lost, the unit will reconnect automatically when you are within range (you may need to get closer to the GLM), but it takes a few minutes.
Home Screen: This is the initial screen that you will see after opening the Android (left screenshot) and iOS (right screenshot) versions of the app. The Android screenshot looks slightly different only because I created a project called “Home Measurements” and I didn’t create any projects on the iPod. The apps function essentially the same, so all remaining screenshots will be of the Android version only. You may note that the “Settings” option is shown on the main screen on the iOS app. For the Android app, Settings are selected from the drop down menu (three vertical dots in the upper right-hand corner).
Real Time Measurements and Downloaded Measurements: The app can be used to collect measurements either in real time or by downloading the data from the GLM. Selecting “Measurements” from the home screen lists all the measurements that were either taken while the app was connected to the GLM or were downloaded, as shown in the left screenshot above. If the measurement was taken while the GLM was connected to your device, then the date and time of the measurement will be listed. If the measurements were downloaded from the GLM (i.e. the measurements were taken while the GLM was not connected to your device), then the timestamp will reflect the download time, not the measurement time.
Selecting the download icon at the top of the screen (the arrow and the line) will download all 30 measurements contained in the memory of the GLM as shown in the right screenshot above.
Editing/Sharing Data: Selecting the drop down menu (three vertical dots in the upper right-hand corner on the Android app or in the lower right-hand corner in the iOS app) and selecting “Edit” allows you to rename each individual measurement.
It is also possible to export the data by selecting “Share” from the drop down menu and selecting how you want to export the data. This will generate a PDF file that contains any sketches or drawings with each measurement (if any exist), and an Excel spreadsheet that contains all the measurements.
Projects: The app also allows the creation of “Projects” to allow measurements to be grouped. Once a project is created, any measurements taken while that project is open will be listed.
The project feature also allows uploading a picture from the job site or drawing. The subsequent measurements taken can easily be added to the picture. The next measurement taken will show up on the picture with the length and an arrow, but the arrow will not necessarily be in the correct spot and will need to be moved. When relocating the arrow on the picture to represent the measurement taken, a close-up view of the arrow end appears as it is selected and moved to make it easier to place it in the correct spot.
The screenshot above shows an example of the final product after the arrow was moved to represent the measurement that was actually taken.
Remote Use: The app can also be used to control the GLM and even change the measurement settings of the device. Selecting “Remote” allows you to take measurements remotely and change the measurement modes and device settings remotely (shown in the left screenshot above).
You can also adjust the GLM settings from the app as shown in the above figure to the right. The measurement settings (units) for the GLM and the app are controlled separately. Changing the settings for the GLM is equivalent to adjusting them on the GLM itself. Changing them for the app controls the units used within the app, regardless of which units were used to take the measurement. This means that if you take all your measurements in feet, within the app you can switch the units to meters and all measurements will be changed, even in the labeled measurements on a picture or drawing.
Use in the Field
I had the opportunity to actually use this device for a project that I am working on for my employer. This project involves replacing a 400 foot long run of header piping in a large mechanical draft cooling tower for a power plant, and I needed to perform field measurements to determine the actual locations of the 24 control valves and 4 pipe reducers. Trying to measure a 400 foot long run of piping with a 25-foot tape measure (our typical measurement tool) would have been a real pain, so I took my GLM 50 C and used it instead (without connecting to my phone to use the app).
I had two fellow engineers with me at the project site. I had one of them hold the target (one of the yellow target cards that came with the unit) at the valve or reducer location while I used the device to shoot the beam to get the measurement to my stationary location. Obstructions around the piping made it challenging to find a placement that worked, and then it became apparent that the greatest challenge was actually hitting the target with the laser beam. In this case, there wasn’t a flat surface available for me to place the GLM on, so I held the GLM free hand. Once my coworker with the target was about 80 feet away, getting the laser to stay on the target while I pressed the Measure button was a challenge, but we were able to make it work. It would have been much easier if I had a tripod to keep the GLM from moving. For our purposes, measurements accurate to within +/- two inches were fine. I had to shift my stationary measurement location several times to get the entire run of pipe covered due to the fact that the piping run was longer than the range of the GLM. We were able to dimension the entire run of piping in about 20 minutes, where it would have probably taken well over an hour with a tape measure. I had a third engineer who was manually recording the measurement values on a drawing of the piping since I didn’t want to deal with the app and using my phone to label each measurement (that would have taken longer). I also didn’t want to use my phone since I was wearing gloves and the environment was fairly dirty. I might have used the app if I didn’t have the third person with me, though. All in all, I was glad that I brought it and it saved us a lot of time. I’d call that a win!
I found the GLM 50 C to be incredibly easy to use and very accurate with a functional and very easy to read display. The numerous functions available make this a very versatile tool. The measurement accuracy of the GLM is only limited by your ability to accurately place the unit as required (perpendicular to a wall, for instance) or to accurately rotate the unit (for indirect height measurements). Therefore linear measurements with the unit flat against a wall or surface were much more accurate, but the indirect measurements with the unit at an angle were less accurate. This is primarily a limitation of how the GLM is used rather than the unit itself. If the unit is mounted to a very sturdy industrial grade tripod, these types of measurements will be more accurate. When trying to “free hand” the unit, it is difficult to keep the laser beam at a single spot, especially when pushing the Measure button due to the force required.
The app provided additional functionality and was the only way to uniquely identify each measurement or reference it by the time it was actually taken, which is essential if you are on a job site and are taking dozens of measurements. I happened to notice that the iOS app would not let me change the GLM settings from the app. Each time I tried to do that, the Bluetooth connection was dropped. Also, since the unit’s memory only holds the last 30 measurements taken, use of the device with the app will be essential for many users. It would have been much better to have more memory on the GLM and at least have the measurements stored in the GLM memory tagged with a time stamp of when the measurement was taken. Connection via Bluetooth would probably not be a problem at most typical construction sites (which is primarily what this unit was designed for), but my job site happens to be a power plant which has areas where radio frequency interference is avoided due to the sensitivity of electronic equipment in the area, and because some areas that are dirty (like the cooling towers discussed above). Therefore, I would tend to resort to the old fashioned method of writing down each measurement on a piece of paper. However, that doesn’t change the fact that this tool is absolutely awesome and a huge step up from a tape measure. I consider it a must for every toolbox.
Continues to work well. The only complaint is that it defaults to a mode with the laser on, and when the laser is on it drains the batteries pretty fast. Lithium batteries are recommended. Also manually changing the mode or shutting of the laser when you aren’t actually taking a measurement is recommended to preserve the batteries.