Topcon GLS-2000 Field Trial Report

Earlier this week we teamed up with Topcon Europe’s scanning specialists who brought their pre-production Topcon GLS-2000 laser scanner to South Wales for some field testing and feedback. Having seen the official specs at the launch in Intergeo, we were keen to test out its capabilities for real on some familiar test sites. First off we visited the Museum of Welsh Life in St. Fagans to scan St. Teilo’s Church, an excellent example of a heritage project. The following day we went the short distance from our offices to Mermaid Quay in Cardiff Bay to test out different scan modes and range.

Note that this was a pre-production unit with in-progress firmware, so many things may change by the time final production takes place (early 2014). We noted several interesting features in the software that were not yet enabled, so won’t mention these until we get a full production model. There’s some exciting stuff in there though!

Having used the older siblings of the GLS-2000 from the very beginning, we already had big muscles from lifting heavy weights to shoulder height (don’t knock them though – excellent wind stability for coastal work!). At just over 11kg, the GLS-2000 is significantly easier to handle yet inherits the robust, workmanlike characteristic of its predecessors via two well positioned aluminium handles. It is IP54 rated and we put this to the test in a small downpour during one of the initial scans. It will even ship in a total station case, so we’re starting to think in terms of ease of use on site along the lines of some of the small phase scanners we’re familiar with. The top carry handle is identical to some of Topcon’s total stations and is easily removable if overhead scanning is needed (however as with the GLS-1500, we seldom needed overhead points as data voids were always more effectively filled by overlapping adjacent scan positions).

Switching on the GLS-2000 takes around 3 minutes of warming up time, and then the first scan is always one minute longer due to the fact that this also includes a one-time calibration routine. The colour touch screen on the side of the instrument is clear and responsive making operation very user-friendly, especially when navigating the scanner to scan ‘top left’ and ‘bottom right’ or areas, or to initialise target scanning (more about target scanning later).

Getting to actually scan is as easy as naming the station and then choosing ‘Start Scan’ after choosing the scan resolution from a pull down list of quick options (e.g. 3.6mm @ 10m, 6.2mm @10m etc.). The only thing to do then is to move out the way fast to avoid being photographed or scanned. The speed of the scanner is impressive, (120,000 in high speed mode). Being a survey grade instrument, it can take longer to set up and level over a survey nail than actual scan time, so we expect massively increased productivity. The GLS-2000 has two laser sources with a variety of modes to suit different scenarios. This is good news for example if you need to operate in an environment where eye-safety is mandatory. Scanner speed is obviously a big issue for the marketing men so see this separate post on “how fast is the Topcon GLS-2000?”

The GLS-2000 has two cameras onboard. We did not test the internal zoom / high detail one, just the external 5 megapixel camera whose lens is found on the outer case just to the right of the scanning mirror.

GLS-2000 camera

Surveying in Practice

As with the previous GLS scanners, there are several modes for scanning several different stations and registering them together:

Method Practice Advantage
Occupation & Backsight Set up and level scanner over survey peg / pin. Scan target set up over known point. (1) Familiar survey practice. (2) No need to have any overlap of scans. (3) Station / BS coordinates can be imported before site work = ready registered clouds on import
Scan 3 or more targets Scan three recognizable targets (e.g. circles), or make detailed scans of (1) Tilts can be disabled (e.g. inverted scanner). (2) Very accurate positioning, ideal for repeat surveys e.g. monitoring
Do nothing Level scanner on tripod and scan. Ensure good overlap with previous scans. Fast with minimal site work and no need for additional targets or georeferencing survey kit (GPS / TS)

We chose the last option “do nothing” although we did do a test involving occupation and backsight (see post on “Target Scanning with the GLS-2000“).

Laser scan prism target

Backsight observation using a conventional prism

The reason for this is because the GLS-2000 is not the only innovative release from Topcon at the time of testing – the ScanMaster processing software will soon include the much anticipated cloud to cloud registration. Our initial tests on this showed that with sufficient overlap of points, it worked flawlessly and was very quick indeed. This alone will revolutionise the workflow in the field and reduce time in the office as well. Because ScanMaster automatically uses any geometric shapes as reference points, we found the secret to this method of working is to work from position to position in a similar way to deploying spheres with other scanners. If automatic cloud to cloud fails for some reason (as in similar geometry inside a square room), crude tie point constraints on matching walls can be quickly added.

A very neat feature that becomes apparent in the software explains why there is a hole in the bottom of the  scanner. There is a mode for measuring the instrument height using the actual onboard laser which is really neat.

No review of an instrument is complete without some data examples. Here are some views; more will follow very soon…

Plan view of scanner positions at St Teilo's church

Plan view of scanner positions at St Teilo’s church

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