OR/15/057 TLS set-up procedures

Jones, L D. 2015. Ground-based geomatic surveys at the BGS - a manual for basic data collection & processing (2015). British Geological Survey Internal Report, OR/15/057.

LPM scanning system (Figure 1)

The location and orientation of the co-ordinate system of the scanner is fixed internally. In general, this scanner co-ordinate system will need to be converted to a known terrain co-ordinate system. In order to minimise the number of parameters involved in the co-ordinate transformation from the scanner system to the known terrain system, it is advised that a baseline be established and the instrument leveled. To do this:

• Set up the instrument, on a tripod, at the first scanning position and locate it with a GNSS receiver. The antenna of the receiver can be mounted on a leveled Tribrach.
• Locate a second tripod at the second scanning position so that once the scanner has completed the scanning from the first position, the scanner and the GNSS receiver may be swapped with each other.
• Place the high-reflectance target on the second tripod after the GNSS observations have been recorded, in order for the laser scanner to take an accurate backsight reading on it. Repeat this cycle as required.

The above procedure allows for the capture of GNSS observation data while the instrument is scanning. At a later stage, the baseline method facilitates the comparison of the GNSS measurements with the observations made with the scanner. The scanner should be setup in the following way:

• Set-up large tripod (splay legs if very windy) and fix the tribrach (3-footed levelling plate) centrally on it, with the leveling screws in the middle of their runs.
• The target bubble of the tribrach should then be leveled using the tribrach foot screws and the adjustable legs of the tripod. Once level, check that the tripod adjustment screws are tightly screwed in.
• Mount the scanner on the Tribrach, so that the three pins are engaged and the instrument is locked in place.
• Ensure that the horizontal angular/azimuth zero mark (short vertical line) is pointing towards the centre of the scan area.
• Attach camera (LPM-i800HA only), telescope, battery, cables, and joystick.
• Turn on in the following order:

- Switch on the Laser Scanner, by pressing the switch once. The laser performs a rotation/elevation check.

- Switch on laptop.

• Level the scanner bubble using the joystick (more accurate).
• Measure the scanner height using the measuring device.

The Laser Scanner is now ready to perform the scan. The software is designed to allow the taking of tiepoints, or backsights, and for taking scan data. To perform the scan carry out the following:

• Start RiProfile. Communications with the scanner will be checked.
• Create a new project. Right-click on SCANS and choose ‘New Scan Position’. Record station name and instrument height.
• Right-click on ‘Scan Position’ and choose ‘New Single Scan’. The scanner will check communications and then open the Scan Window.
• Choose Top, Right, Bottom, Left extents of the scan. This is defined using the joystick and then pressing the corresponding button.
• Choose a scan increment, the smaller the interval, the tighter the scan and the more time needed. The display will show the estimated time and number of points for the scan. Press OK when happy.
• Confirm by pressing OK. The scan will begin automatically.

When the scan is finished it will be automatically saved. To take tiepoints to points with known coordinates, in order to properly orient the scan, you should do the following:

• Right-click on TIEPOINTSCANS and choose ‘New Tiepoint Scan’. Record name.
• Choose Top, Right, Bottom, Left extents of the scan. Press OK when happy.
• Confirm by pressing OK. The scan will begin automatically.

In order to colour the scans, photographs are required (LPM-i800HA only) by doing the following:

• Turn on the Camera and wait for the laptop to register the connection.
• Right-click on the Scan and choose ‘Image Acquisition’. Check angles, overlap and number of images. Click OK. The camera will automatically take the required number of photographs.

When all the Scans and tiepoints are completed the Laser Scanner can be switched off, packed away and moved. This is done as follows:

• Select Tools, Scanner Control. Choose Park.
• Turn the Scanner off by pressing the switch once. It will make an audible tone and switch itself off.
• Turn off the Camera and laptop. Disconnect the telescope and all cables. Dismantle the scanner and place back in the box before moving.

VZ scanning system (Figure 2)

The location and orientation of the co-ordinate system of the scanner is fixed internally. It can either be done via an internal GNSS or the Leica Viva GNSS system (better accuracy). This can be done via the ‘baseline’ (previously stated) or ‘scan and move’ techniques. The latter is carried out as follows:

• Set up the high-reflective tiepoint on a ranging-pole, or tripod, in a central area observable from all scan positions.
• Set-up the scanner on a tripod and level using the Tribrach.
• Establish the co-ordinates of both using the GNSS receiver. This can be done on-the-pole for the tiepoint and then mounted on the top of the scanner, which can then be moved independently as required.

The scanner should be setup in the following way:

• Set-up large tripod (splay legs if very windy) and fix the tribrach (no always required) centrally on it, with the leveling screws in the middle of their runs.
• The target bubble of the tribrach should then be leveled using the tribrach foot screws and the adjustable legs of the tripod. Once level, check that the tripod adjustment screws are tightly screwed in.
• Mount the scanner on the Tribrach, so that the three pins are engaged and the instrument is locked in place.
• Attach camera, GNSS, external battery (if required) and laptop (if required).
• Turn on in the following order:

- Switch on the Laser Scanner, it performs a rotation check.

- Switch on laptop.

- Switch on Camera.

• Level the scanner using the internal bubble (more accurate).
• Measure the scanner and GNSS height.

The Laser Scanner is now ready to perform the scans. To perform the preview scan carry out the following:

• Start RiScanPro. Communications with the scanner will be checked.
• Create a new project. Right-click on SCANS and choose ‘New Scan Position’. Record station name and instrument height.
• Right-click on ‘Scan Position’ and choose ‘New Single Scan’. The scanner will check communications and then open the Scan Window.
• Choose ‘Panorama Scan’, 0.1 deg. as ‘Increment’ and press OK.
• Confirm by pressing OK. The scan will begin automatically.

When complete the scan will save automatically. To perform the precise scan:

• Right-click on ‘Scan Position’ and choose ‘New Single Scan’. The scanner will check communications and then open the Scan Window.
• Choose ‘Scan’, 0.05 deg. as ‘Increment’ and press OK.
• Make sure ‘Image Acquisition’ is turned on.
• Press OK.
• Confirm by pressing OK. The scan and photographs will begin automatically.

When complete the scan will save automatically To take tiepoints, do the following:

• In the 2D Scan Window, mark the tiepoints. Click the ‘fine scan all targets’ icon. The scanner will carry out an ultra-fine scan and automatically locate the centre of each tiepoint.

When all the Scans and tiepoints are completed the Laser Scanner can be switched off, packed away and moved.