Terrestrial laser scanning

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Terrestrial laser scanner with screwed-on GNSS receiver

The terrestrial laser scanning (TLS) or terrestrial LiDAR (Light Detection And Ranging) is detected in a stationary, active, imaging 3D method, the laser-based distance measurements in an automated sequence of quasi-equidistant sampling intervals in vertical and horizontal directions and geometric therefrom information about the object wins. The mode of operation of a laser scanner differs from other measuring methods in that the laser scanner is used to detect an area over a regular grid and not, as is usual, an object discretization using representative points.

Data acquisition

geometry

The raw data that is generated by a laser scanner are measured value triples, consisting of a measured inclined distance and a value each for the horizontal and vertical deflection. Different methods are used for distance measurement depending on the manufacturer. A distinction is made between the pulse transit time method , the phase difference method and the triangulation method . The scanning, i.e. H. the determination of the vertical or horizontal values ​​can be done in different ways. In addition to scanning by servomotors that move the laser, rotating plane mirrors or a continuously rotating mirror polygon can be used by servomotors. Manufacturers often use a combination of different types of scanning.

The recorded polar coordinates are converted into Cartesian coordinates using simple trigonometric relationships . This intermediate result represents a point cloud, which can then be further processed on the computer, for example to generate 3D models. There are also fundamental differences in modeling compared to conventional methods, since no previously defined discrete object point is measured, but rather a large number of points randomly distributed on the measurement object. The geometric representation points must therefore be determined by geometric algorithms in post-processing.

Registration of remission intensity and color information

If, in addition to the geometric data, intensity information of the reflected laser measurements is also registered, one can also speak of 4D laser scanning, whereby the fourth dimension is not to be understood here as a temporal resolution in the sense of a 3D film or as a fourth spatial dimension. With the aid of the intensity information, the three-dimensional point clouds obtained can be coded with false colors, which is often sufficient for basic object differentiations within the point cloud. Internal or external digital cameras can be used to supplement real color information, for example with RGB images. Internal cameras are mostly compact cameras with low resolution and color quality - they are primarily used to color the point cloud quickly. Significantly better results are achieved if an external SLR camera is installed. The combination with RGB information can later increase the quality of the model. B. Possible applications in the field of virtual reality .

Designs and market overview

In terms of designs, two types of laser scanner systems have established themselves, which differ in their field of view. The laser scanners can be divided into the classes panorama scanners and camera view scanners. With camera view scanners, the field of view is clearly limited both horizontally and vertically. Panorama scanners can work in a field of view of 360 ° horizontally and ± 30 ° to 180 ° vertically. B. is an advantage when taking a picture of the interior because theoretically (with a clear view) the number of scans is reduced compared to a camera view scanner.

Since the development of the first terrestrial laser scanner in 1999, there has been a rapid development on the hardware side. The laser scanner systems became faster and lighter over time, but only slightly more accurate. Newer systems also measure over much greater distances and are more likely to be equipped with a color camera. The following table is intended to give an overview of current and historical 3D laser scanners:

Manufacturer system Launch Distance measurement principle Range [m] Measuring rate [points / s]
CLAUSS RODEON scan 2012 Impulse transit time 250 14400
CLAUSS RODEON smartscan 2013 Impulse transit time 250 14400
Cyra Technologies Cyrax 2400 1998 Impulse transit time 100 800
Cyra Technologies Cyrax 2500 2000 Impulse transit time 100 1000
Faro Technologies Photon 80/20 2008 Phase difference 76 120000
Faro Technologies Photon 120/20 2009 Phase difference 153 976000
Faro Technologies Focus 3D 120 2010 Phase difference 120 976000
Faro Technologies Focus 3D X 330 2013 Phase difference 330 976000
IQvolution IQSun880 / LS 880/840 2004 Phase difference 76 120000
IQvolution IQSun420 / LS 420 2005 (?) Phase difference 20th 12000
Leica Geosystems HDS3000 2002 Impulse transit time 300 4000
Leica Geosystems HDS4500 2003 Phase difference 53.5 125000
Leica Geosystems ScanStation 2005 Impulse transit time 300 4000
Leica Geosystems ScanStation 2 2007 Impulse transit time 300 50000
Leica Geosystems HDS6000 2007 Phase difference 79 500000
Leica Geosystems ScanStation C10 2009 Impulse transit time 300 50000
Leica Geosystems HDS4400 2009 Impulse transit time 700 4400
Leica Geosystems HDS6100 2009 Phase difference 79 508000
Leica Geosystems HDS6200 2010 Phase difference 79 1016727
Leica Geosystems HDS7000 2011 Phase difference 187 1016727
Leica Geosystems HDS8400 2012 (?) Impulse transit time 1000 8800
Leica Geosystems ScanStation P20 2012 Impulse transit time 120 1000000
Leica Geosystems HDS8800 2012 Impulse transit time 2000 8800
Maptek I-site 8800 2010 Impulse transit time 2000 8800
Maptek I-site 8400 2011 Impulse transit time 1000 8800
Riegl LMS-Z420i 2003 Impulse transit time 1000 11000
Riegl LMS-Z390i 2006 Impulse transit time 400 11000
Riegl LPM-321 2007 Impulse transit time 6000 1000
Riegl VZ-400 2008 Impulse transit time 500 125000
Riegl VZ-1000 2010 Impulse transit time 1400 122000
Riegl VZ-4000 2012 Impulse transit time 4000 222000
Riegl VZ-6000 2012 Impulse transit time 6000 222000
Topcon GLS-1500 2010 Impulse transit time 330 30000
Trimble Navigation GS 200 3D 2005 Impulse transit time 200 5000
Trimble Navigation FX 2009 Phase difference 46 190000
Trimble Navigation CX 2010 Combination phase & pulse 80 54000
Trimble Navigation TX5 2012 Phase difference 120 976000
Zoller + Fröhlich IMAGER 5006Ex 2009 Phase difference 79 508000
Zoller + Fröhlich IMAGER 5006h 2010 Phase difference 79 1016727
Zoller + Fröhlich IMAGER 5010 2010 Phase difference 187 1016027
Zoller + Fröhlich Z + F PROFILER 6007 duo 2011 Phase difference 79 1016000
Zoller + Fröhlich Imager 5010C 2012 Phase difference 187 1016000
Zoller + Fröhlich Imager 5010X 2015 Phase difference 187 1016000
Zoller + Fröhlich Profiler 9012 2012 Phase difference 119 1016000
Pulsar Measuring Systems PMS 500 ? Impulse transit time 8000 3.3
Pulsar Measuring Systems PMSImpulse 100LR ? Impulse transit time 400 3.3
Basic software Surphaser 25HSX ? Phase difference 70 1200000
MDL Laser Systems C-ALS 2009 (?) Impulse transit time 150 250
MDL Laser Systems VS150 2009 (?) Impulse transit time 300 200
MDL Laser Systems Quarryman Pro 2009 (?) Impulse transit time 600 250
MDL Laser Systems Quarryman Pro LR 2011 (?) Impulse transit time 1200 250
MDL Laser Systems Dynascan HD100 2012 Phase difference 120 976000

evaluation

Georeferencing, co-referencing, registration

Depending on the project requirements, the object is captured from one or more points of view with different angles of the object to be captured. The point cloud is obtained in a local coordinate system as the result of each individual point of view. In the further course of the evaluation, the individual local point cloud systems must be connected to one another (co-referencing) and possibly referenced to a higher-level coordinate system (georeferencing in the case of earth-based spatial reference systems). This step is called registration in English and is often incorrectly translated as registration instead of referencing. There are several approaches to referencing, such as B. Referencing via fitting surfaces of standard geometries (plane, sphere, cylinder), via manually selected identical points of the point clouds, via retroreflective target marks and via flat target marks with a special pattern with regard to the reflectance values ​​(figurative marks with e.g. checkerboard pattern or white circle on a black background ). The ICP ( iterative closest point ) is used as a brandless solution . Here, areas are segmented in the overlap area of ​​two point clouds, in which approximately identical points are then selected by determining the shortest distance. An approximation of the two point clouds can then be achieved iteratively by spatial similarity transformations. The referencing result is a point cloud, which ideally discriminates all object surfaces and is suitable for further modeling, combination with other geographic information and visualization.

Modeling

By supplying special specialist knowledge, a model of the real object can be generated from this data record. For example, certain areas can be selected from the overall point cloud in order to approximate geometric primitives such as planes or cylinders using certain algorithms. These can then be intersected to form an edge surface model.

Floor plans, views and sections can also be created.

The part of the evaluation in particular is very labor-intensive and therefore costly due to the lack of automation. The process flow from object acquisition to referencing and modeling to visualization should be able to be automated due to the complete data availability in the computer. First approaches to this were z. B. 2003 described by Fredie Kern (see literature).

Areas of application

The possibility of non-contact and extensive measurement in combination with automated processing results in many areas for which laser scanning is an interesting method. Terrestrial laser scanning can often be used economically wherever complex objects need to be scanned quickly and over their entire surface without contact. Terrestrial laser scanning is therefore a useful addition to conventional - in comparison more precise - measuring methods such as photogrammetry or tacheometry . A synergy of the measurement processes laser scanning, photogrammetry and tachymetry as well as an automation of the evaluation process will be able to economically exploit the full potential of terrestrial laser scanning in the future and thus enable optimal geometry management.

Applications in building surveillance

In addition to elastic deformations within certain limits, deformations of structures can become plastic due to excessive forces or wear and tear, and the structures can become statically unstable as a result. In order to guarantee the function of such structures, a regular check for deformation processes is necessary. Among other methods (visual, mechanical, chemical controls) provides TLS next tachymetric surveying , leveling measurements or GNSS measurements a possibility of geometric control and is suitable for monitoring of various structures such as dams, bridges, towers, tall buildings or railway tracks.

When using TLS for geometric structural deformation measurement, a large number of points can be measured in a short time (compared to other geometric methods). Due to the grid-like scanning, however, the points are not exactly reproducible for multi-temporal recordings, so TLS is usually referred to as a two-dimensional measuring method in building monitoring. Changes can be extracted from multitemporal measurements, whereby between periodic variations (e.g. in the context of temperature fluctuations or water level fluctuations, load-dependent changes in bridges), sudden changes (e.g. avalanche damage) and linear changes (e.g. in succession from continuous lowering of the groundwater level). The desired accuracy for deformation measurements is in the millimeter range. Deformations can be revealed based on relative or absolute deformation. Relative deformation detection results from difference images between 2 or more measurements. For absolute deformation detection, the measurements must be registered in a geodetic reference system, with the deformations then being able to be determined precisely in a coordinative manner. Different approaches are used in the comparison: With the block approach, the surface of the building is regularly rasterized and a representative point per raster cell is determined by averaging. With the 3D area comparison, areas are generated from the measured points with the help of triangular meshing, and the shortest distance between points or areas from previous measurements is calculated in the course of the subsequent measurement.

Applications in geosciences

TLS has a wide range of applications in the geosciences, but is still in its infancy. The main focus is on the recording and visualization of temporal changes (time series) , mapping of rockfall and gravitational mass movements , mass balancing and monitoring as well as geohazard research TLS recordings can be made with high spatial resolution and high accuracy over distances of several hundred meters to kilometers . High-resolution TLS data are also used in areas at risk in risk management and spatial planning .

Landslides are widespread risks which anthropogenic structures such as roads, dams and power lines can cause considerable damage. TLS observations provide reliable data for the creation of mass balances of the landslide and associated map material. Furthermore, on the basis of the TLS data, superficial movement patterns, movement rates can be derived and moving volumes can be estimated.

The application potential of TLS in alpine mountain areas is very diverse. Among other things, the monitoring of destabilized rock faces. Increased glacier retreat and advancing permafrost degradation are the cause of the instability in rock faces. The resulting rockfall can have serious economic and social consequences for people , infrastructure and settlements in the Alpine region.

Applications in archeology

Archaeological sites and artifacts used to be documented with simple sketches and photographs. Due to the increasing progress of laser scanning technology, the TLS is also being used more and more in archeology. Archaeological documentation as well as the analysis of archaeological sites and artefacts are simplified by the creation of 3D models . Furthermore, the resulting point clouds are suitable for restoration , conservation , true-to-scale reproductions, monitoring of changes and serve as a basis for the subsequent interpretation of the historical finds. The advantages of laser scanning technology, such as the high speed and accuracy of the measurements as well as the suitability for use in hard-to-reach areas and independence from time of day and weather , are of great use for archaeological documentation. However, the large amount of data generated by laser scanning recordings proves to be very problematic and must be reduced. The lengthy post-processing and the limited field of view - because with TLS no bird's-eye views can be recorded - represent further disadvantages for the use of the TLS in archeology. The combination with ALS data, such as terrain models or photogrammetric recordings, enables more precise results or a simplified interpretation can be achieved.

In principle, the TLS is an efficient method for archaeological documentation and analyzes and the results offer a good starting point for comprehensive interpretations. In archeology, however, laser scanning data will not replace field trips or manual recordings for documentation, but should rather be viewed as a useful addition.

Applications in city modeling

Thanks to the possibility of creating a digital, three-dimensional image of cities, districts or individual buildings by means of laser scanning , TLS can also be used in the field of 3D city modeling.

All recording methods of laser scanning contribute to the growing number of available cities and levels of detail . While TLS is particularly suitable for the detection of facades and objects in the street space, the combination with ALS , the inclusion of systems such as mobile mapping and other methods enables the creation of entire city models. The latter is strongly promoted by various developments by the major manufacturers in the form of specific solutions for various modes of transport and issues.

The greatest development can currently be observed in the area of ​​automation. In the present context, this means the computer-aided, automatic execution of as many work steps as possible - from georeferencing, co-referencing, registration to the extraction, classification and attribution of individual objects from the point cloud to the fully automatic creation of entire models.

After processing the output data, further processing of the data is possible in numerous fields of application in the field of visualization, animation and simulation, including 3D real-time in city modeling or traffic area monitoring .

Further areas of application

Further areas of application are geometrical building surveys , facility management , quality assurance in construction and mechanical engineering, preservation of evidence , accident site documentation, visualization , animation or simulation . Projects to further develop autonomous driving - in particular self -driving vehicles such as the Google Self-Driving Car Project - also use LiDAR systems in some cases.

literature

  • Karl Kraus: Photogrammetrie Volume 1, Geometric information from photographs and laser scanner recordings. 7th, fully revised and expanded edition, deGruyter textbook, 2004
  • Fredie Kern: Automated modeling of building geometries from 3D laser scanner data. Dissertation, Geodetic Series of the Technical University of Braunschweig, Issue 19, 2003
  • George Vosselman and Hans-Gerd Maas (Eds.): Airborne and Terrestrial Laser Scanning , Dunbeath 2010.
  • George L. Heritage and Andrew RG Large (Eds.): Laser Scanning for the Environmental Sciences , Chichester 2009.
  • Matti Maltamo, Erik Naesset and Jari Vauhkonen (eds.): Forestry Applications of Airborne Laser Scanning , Heidelberg / New York / London 2014.

Web links

Individual evidence

  1. ↑ a b c d e f g h Engström, T., Johansson, M .: The use of terrestrial laser scanning in archeology. Evaluation of a Swedish project, with two examples . In: Journal of Nordic Archaeological Science . tape 16 , 2009.
  2. ↑ a b c d e f g h Groh, S., Neubauer, W .: Use of a terrestrial 3-D laser scanner in Ephesus . In: Annual books of the Austrian Archaeological Institute in Vienna . tape 72 , 2003.
  3. ↑ Vosselman G. Maas H.-G .: Airborne and Terrestrial Laser Scanning . Whittles Publishing, Dunbeath, Scotland, UK 2010, ISBN 978-1-904445-87-6 .
  4. ↑ Rabah, M., Elhattab, A., Fayad, A .: Automatic concrete cracks detection and mapping of terrestrial laser scan data . In: Journal of Astronomy and Geophysics . No. 2 , 2013, p. 250-255 .
  5. ↑ a b c d e f g h i j k l Lerma, J., Navarro, S., Cabrelles, M., Villaverde, V .: Terrestrial laser scanning and close range photogrammetry for 3D archaeological documentation: the Upper Palaeolithic Cave of Parpalló as a case study . In: Journal of Archaeological Science . tape 37 , no. 3 , 2010.
  6. ↑ Vosselmann, G. Maas, H.-G .: Airborne and Terrestrial Laser Scanning . Whittles Publishing, Dunbeath 2010, pp. 342 .
  7. ↑ Hildebrandt, R., Iost, A .: From points to numbers: a database-driven approach to convert terrestrial LiDAR point clouds to tree volumes . In: European Journal of Forest Research . No. 131 , 2012, p. 1857-1867 .
  8. ↑ Hildebrandt, R., Iost, A .: From points to numbers: a database-driven approach to convert terrestrial LiDAR point clouds to tree volumes . In: European Journal of Forest Research . No. 131 , 2012, p. 1857-1867 .
  9. ↑ Ying Yang, M., Cao, Y., McDonald, J .: Fusion of camera images and laser scans for wide baseline 3D scene alignment in urban environments . In: Journal of Photogrammetry and Remote Sensing . No. 66 , 2011, p. 52-61 .
  10. ↑ Vosselmann, G. Maas, H.-G .: Airborne and Terrestrial Laser Scanning . Whittles Publishing, Dunbeath 2010, pp. 342 .
  11. ↑ Heritage, G., Large, A .: Laser Scanning for the Environmental Sciences . Wiley-Blackwell Publishing, West Sussex 2011, pp. 302 .
  12. ↑ Niemeier, W., Kern, F .: Application potentials of scanning measurement methods (PDF; 1.4 MB)
  13. ↑ 2400 ACD Enterprises - 3D Laser Imaging ( Memento of the original from May 29, 2009 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / users.nlc.net.au
  14. ↑ 3D scanning with the aim of rapid manufacturing - i3mainz ( memento of the original from October 19, 2007 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / www.i3mainz.fh-mainz.de
  15. ↑ Faro Photon 80/20 ( Memento of the original from April 17, 2012 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF; 3.3 MB) @1@ 2Template: Webachiv / IABot / www.faro.com
  16. ↑ Faro Laser Scanner Photon 120/20 ( Memento of the original from September 25, 2011 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / www.faro.com
  17. ↑ a b Faro Laser Scanner Focus 3D
  18. ↑ iQsun 880 HE80 3D laser scanner
  19. ↑ FARO Laser Scanner LS 840/880  ( page no longer available , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.@1@ 2Template: Dead Link / www.faro.com  
  20. ↑ FARO Laser Scanner LS 420  ( page no longer available , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. (PDF; 141 kB)@1@ 2Template: Dead Link / www.faro.com  
  21. ↑ a b c d e f g h i j k l m Leica Geosystems - HDS Hardware
  22. ↑ a b Maptek - I-Site 3D Laser Scanning Technology
  23. ↑ a b c d e f g RIEGL - Terrestrial Scanning
  24. ↑ GLS 1500 - Topcon Positioning Systems, Inc.
  25. ↑ Trimble GS 200 3D Scanner ( Memento of the original from August 20, 2012 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / www.trimble.com
  26. ↑ Trimble FX Scanner ( Memento of the original from January 31, 2010 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / www.trimble.com
  27. ↑ Trimble CX scanner
  28. ↑ Trimble TX5 scanner
  29. ↑ a b c d e f g ZF laser products
  30. ↑ a b Pulsar Measuring Systems
  31. ↑ Surphaser 3D scanner
  32. ↑ a b c d e MDL Laser Systems
  33. ↑ Guan, Y., Zhang, H .: Initial Registration for Point Clouds Based on Linear Features . In: Fourth International Symposium on Knowledge Acquisition and Modeling (KAM), 8-9. Oct. 2011, Sanya . 2011, p. 474-477 .
  34. ↑ Vosselmann, G. Maas, H.-G .: Airborne and Terrestrial Laser Scanning . Whittles Publishing, Dunbeath 2010, pp. 342 .
  35. ↑ Pfaffenholz J.-A., Bae, K.-H .: Geo-referencing point clouds with transformational and positional uncertainties . In: Journal of Applied Geodesy . No. 6 , 2012, p. 33-46 .
  36. ↑ Fan, L., Atkinson, PM: Accuracy of Digital Elevation Models Derived From Terrestrial Laser Scanning Data . In: Geoscience and Remote Sensing Letters . No. 12/9 , 2015, p. 1923-1927 .
  37. ↑ Kawashima, K., Kanai, S., Date, H .: Automatic Recognition of a Piping System from Large-Scale Terrestrial Laser Scan Data . In: International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences . XXXVII - 5 / W12, 2011, p. 283-288 .
  38. ↑ Alba, M., Fregonese, L., Prandi, F., Scaioni, M., Valgoi, P .: Structural Monitoring of a Large Dam by Terrestrial Laser Scanning . In: International Archives of Photogrammetry, Remote Sensing and Spatial Information Sciences . tape 36 , no. 5 , 2006.
  39. ↑ González-Aguilera, D., Gómez-Lahoz, J., Sánchez J .: A new approach for structural monitoring of large dams with a three-dimensional laser scanner . In: Sensors . tape 8 , no. 9 , 2008, p. 5866-5883 .
  40. ↑ Zogg, H.-M., Ingensand, H .: Terrestrial Laser Scanning for Deformation Monitoring - Load Test on the Felsenau Viaduct (CH) . In: The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Science . tape 37 , B5, 2008, p. 555-561 .
  41. ↑ Schneider, D .: Terrestrial laser scanning for area based deformation analysis of towers and water dams . In: Proc. of 3rd IAG / 12th FIG Symp., Baden, Austria, May 22.-24 . 2006.
  42. ↑ Soni, A., Robson, S., Gleeson, B .: Structural monitoring for the rail industry using conventional survey, laser scanning and photogrammetry . In: Applied Geomatics . 2015, p. 1-16 .
  43. ^ Eling, D .: Terrestrial laser scanning for building surveillance . Publishing house of the Bavarian Academy of Sciences in commission from Verlag CH Beck, Munich 2009, ISBN 978-3-7696-5053-2 .
  44. ↑ Mecheleke, K., Lindstraedt, M., Sternberg, H., Kersten, T .: Building monitoring with terrestrial laser scanning . In: Luhmann, T., Müller, C. (Eds.): Photogrammetry, Laserscanning, Optical 3D Measurement Technology - Contributions to the Oldenburg 3D Days 2012 . VDE Verlag GmbH, Berlin and Offenbach 2012, ISBN 978-3-87907-515-7 , p. 55-62 .
  45. ↑ a b c Kenner R., Phillips M., Danioth C., Denier C., Thee P. & Zgraggen A .: Investigation of rock and ice loss in a recently deglaciated mountain rock wall using terrestrial laser scanning: Gemsstock, Swiss Alps . In: Cold Regions Science and Technology . No. 67 , 2011.
  46. ^ Kuhn D. & Prüfer S .: Costal cliff monitoring and analysis of mass wasting processes with the application of terrestrial laser scanning: A case study of Rügen, Germany. In: Geomorphology . No. 213 , 2014.
  47. ↑ a b Zeybek M. & Sanhoglu I .: Accurate determination of the Taskent (Konya, Turkey) landslide using a long-range terrestrial laser scanner. In: Bulletin of Engineering Geology and the Environment . No. 74 , 2015.
  48. ↑ a b c d e f Kersten, Th., Lindstaedt, M., Mechelke, K., Vogt, B .: Terrestrial Laser Scanning for the Documentation of Archaeological Objects and Sites on Easter Island . In: Computer Applications and Quantitative Methods in Archeology . 2010.
  49. ^ Jansa, Josef & Stanek, Heinz: Deriving city models from laser scanner data, floor plans and photographic recordings . In: VGI - Austrian Journal for Surveying and Geoinformation . No. 91 (4) , 2003, p. 262-270 ( online (PDF)).
  50. ^ Jansa, Josef et al .: Terrestrial Laserscanning and Photogrammetry - Acquisition Techniques complementing one another . In: ISPRS Archives . 2004 ( Online (PDF)).
  51. ^ Riegl Mobile Mapping
  52. ↑ Leica Mobile Mapping
  53. ↑ Pu, Shi & Vosselmann, George: Automatic Extraction of Building features from terrestrial laser scanning . In: ISPRS Archives . 2006 ( Online (PDF)).
  54. ↑ Pu, Shi & Vosselmann, George: Knowledge based reconstruction of building models from terrestrial laser scanning data . In: ISPRS Journal of Photogrammetry and Remote Sensing . No. 64 , 2009, p. 575-584 ( Online (PDF)).
  55. ↑ Kress, Lorenz et al .: 3D city modeling and traffic area detection with laser measurement technology . ( Online (PDF)).
  56. ^ Google Self-Driving Car Project