Multi-function Laser Disto

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Multi-function Laser Disto

Postby caver.adam » May 8, 2012 9:50 am

I've seen some reports out there on modifying a laser disto to show digital compass and inclination readings, but most of the documents I can find are several years old and use outdated technology or obsolete distos. I was wondering if anyone out there has recent experience. I'm looking at building my own that will work in a newer model ditance meter. Possibly making some changes so that it will be possible to calibrate for multiple devices.

I'm thinking about using an LSM303DLHC digital compass and accellerometer to make a tilt-compensated compass and then connect that to a laser disto using one of the methods I've seen in previous reports. This compass has a resolution of 2mGauss which should equate to easily .5 degree resolution. Haven't had time to work the numbers to figure out the accuracy yet.

Thoughts are this:

Remove the battery pack and connect an external battery pack with regulators both in the battery pack and in the disto (to decrease soft-iron effects).
In place of the battery pack put a circuit with the tilt compensated compass.
Have the microcontroller for the compass module read normal outputs to the LCD and overwrite with compass data to the LCD screen.
Have access to calibration buttons through the battery case door for calibration of the digital compass.

The digital compass should be calibrated to magnetic north as accurately as possible. Whenever soft-iron effects could change the compass will need to be re-calibrated.

Anyone have any experience with this chip? Any advice or time-savers?
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Re: Multi-function Laser Disto

Postby kdxn » May 8, 2012 1:55 pm

Been done.
See DistoX for Disto A3 and DistoX2 for Disto DXT.
Multiple threads in the Surveying section.

You will need to decide which Disto to integrate with and then find the internal control lines for the display.
Decode the display so that you know how to program it with your tilt and compass values.
If you want to Bluetooth the data to a PDA then you will need to read the laser range from the display or from internal data lines.

Batteries are a problem for compass calibration. Also need to take care of any significant temperature drift effects.

The DistoX uses the PNI 11096 magnetic chip now obsolete, and the VTI SCA3000-D02 for tilt which is also now obsolete.
The DistoX2 uses the Honeywell HMC5883 magnetic chip and the BMA180 for tilt. Ongoing calibration drift issues with this design which are being worked on.

The Leica Disto models change every few years and the display segments change.
Latest models are the D210 and X310.

Good luck !
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Re: Multi-function Laser Disto

Postby lleblanc » May 9, 2012 9:05 am

Hi,

You may check some relevant articles In the CREG Journal (http://bcra.org.uk/creg/jnl/):

By Scurion maker Martin Melzer:

2003 How to Design an Electronic Surveying Instrument, No. 54 pp 12-15.

By DistoX maker Beat Heeb:

2009 An All-In-One Electronic Cave Surveying Device, No. 72 pp 8-10
2010 A General Calibration Algorithm for 3-Axis Compass/Clinometer Devices, No. 73 pp 12-18
2010 General Calibration Algorithm - Corrections No. 75 pp 22
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Re: Multi-function Laser Disto

Postby caver.adam » May 9, 2012 1:14 pm

Thanks for the feedback and links. I appreciate it. I was reading the 2009 item before.

I notice that the HMC5883 has 8mGauss resolution and fairly low accuracy. I think I'll have to reach out to the DistoX2 team so I don't double work here. Some of my interest is in physicially moving the batteries to decrease calibration effects due to the batteries and simultaneously create room for a board to be inserted.
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Re: Multi-function Laser Disto

Postby lleblanc » May 9, 2012 1:36 pm

sampson.adam wrote:Thanks for the feedback and links. I appreciate it. I was reading the 2009 item before.

I notice that the HMC5883 has 8mGauss resolution and fairly low accuracy. I think I'll have to reach out to the DistoX2 team so I don't double work here. Some of my interest is in physicially moving the batteries to decrease calibration effects due to the batteries and simultaneously create room for a board to be inserted.


AFAIK, the DistoX2 team is Beat Heeb alone.

Moving the batteries was tried on the Toposcan aka EasyTopo prototype (never made it to market) and it was a pain. The batteries were taped along the serial cable that connected the device to the receiving PDA and had to be stretched so the batteries wouldn't end up getting close to the device.
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Re: Multi-function Laser Disto

Postby caver.adam » May 9, 2012 6:39 pm

Yeah. I can see it being a pain, especially when crawling where it can get caught. I was thinking about using a power cable much like the one on my headlamp. I'll probably re-think that.
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