Addendum to the 1979 National Mapping Technical Report 26 ‘Laser Terrain Profiler’ by Paul Wise followed by John Manning’s 1989 paper on LAPS



National Mapping acquired a new laser during the 1984-85 financial year which was integrated into a smaller, compact, digitally based profiling system. This system operated in a Cessna C421 which had replaced the Nomad.


The ACCI (Associated Controls and Communications, Inc. of Cambridge, Massachusetts, USA) PRAM laser was coaxially sited with the existing 70mm strip camera and along with the existing BRU (Barometric Reference Unit) and new control console and data capture system, formed the Natmap PRAM profiling system.

The 30pps (pulses per second) YAG transceiver employed a pulsed Nd:YAG (neo­dymium-doped, yttrium-aluminum-garnet) laser operating at 1064 nanometers with a 10 nanosecond pulse width and 0.5 milliradian beam width. Also included was the laser transceiver and control console, including power supplies, associated electronics, nanosecond time interval counter, height computer, control panel, display and interfaces for recording and remote control. An Intel 86/05 single board computer performed all mathe­matical calculations, diagnostics, range gating, computer to computer interfaces, range conversions and had output func­tions for an RS-232 interface. It was capable of at least ±10cm accuracy in all conditions and all up weighed only 20kgs (Jepsky, 1986).

The complete airborne system was designed in-house so that each time the laser “fired” and digitally recorded a “height” its location was recorded on the strip camera and a digital BRU reading was also captured.


Digital capture enabled in-house developed, computerised post-processing, eliminating the previous, tedious and error prone, manual height point determinations as described in Wise (1979).


The location of height points were digitised from the strip film and immediately related to their relevant “raw” height by the computer. In addition, any correction provided by the BRU could be applied as well as “misclose” corrections provided by relating appropriate profiles to AHD bench marks, thus delivering the “final” heights on AHD.


Operationally this system provided supplementary vertical control for mapping at various scales within Australia. However, it is more noted for working on a 1989 overseas aid project, in conjunction with a similarly devised Canadian system, in Indonesia. The Canadians worked in Kalimantan and the Australians operated the Natmap equipment in Sulawesi (Lines, 1992).



Paul Wise (2011)




Jepsky, J. (1986) Airborne laser profiling and mapping systems come of age. Tech. Pap. March 1986 ACSM-ASPRS Annual Convention, Washington D.C. Vol. 4, Photogrammetry, 229-238.


Lines, J.D. (1992) Australia on Paper: The Story of Australian Mapping. Box Hill: Victoria, Fortune Publications, 1992, ISBN 0 646 09769 5.


Wise P. J. (1979) 'Laser Terrain Profiler' Division of National Mapping Technical Report No. 26, Copyright © Commonwealth of Australia, Geoscience Australia, (1979).



Operator’s console in Cessna 421     

Laser and receiver in Cessna 421


Ground profile recorded on 70mm film related to profile by timecode


Digitiser input

Profile display


Computer controller and input




The AUSLIG Laser Airborne Profiling System


Australian Surveying and Land Information Group, Canberra





The current airborne laser profiling system used in the Australian Surveying and Land Information Group is the Laser Airborne Profiling System (LAPS). It was developed within AUSLIG principally to provide a means of replacing old radar profiling in areas of marginal accuracy for 20 metre contouring and to satisfy a need for vertical control suitable for 10 metre topographic mapping at 1:50 000 scale. It is installed in a Cessna 421 aircraft as an optional configuration to an RC10 camera.





Vertical control for photogrammetric plotting from aerial photography for most of the National Topographic Map Series at 1:100 000 and for 1:50 000 scale topographic mapping across Australia has been provided by airborne profiling techniques, using radar, continuous wave laser or pulsed laser technology. A historical review of the vertical control used for the topographic mapping of the Australian continent is given in Manning and Menzies (1988). This paper describes the Laser Airborne Profiling System currently in service within the Australian Surveying and Land Information Group.


The requirement for a new system arose when the WREMAPS I, continuous wave laser profiler reached the end of its economic life. Past experience with laser profiling from fixed wing aircraft had demonstrated the low cost of obtaining vertical control over large areas of Australia, particularly in remote or inaccessible country. Although the new system was more a lateral step than a direct advance in technology, it was designed principally as a means to upgrade old radar profiling in accuracy during 1:100 000 revision and to meet 1:50 000 specifications for 10 metre contouring where required.


Using the national geodetic framework and the existing levelling network, the use of a fixed wing aircraft in stable conditions enables lines of over 100 km to be profiled. The benefits of the speed and range of a fixed wing aircraft and the elimination of the need for any ground party produce a very economic but powerful mapping tool which can be mobilised to any work area in Australia at short notice.


In the 1980s a new wave of laser profiling technology was introduced by Associated Controls and Communications, Inc (ACCI) from Salem Massachusetts USA. In 1982 a new airborne terrain profiler, the PRAM III, was introduced incorporating ACCI's one nanosecond ultra high speed interval counter, providing range accuracies of ±15 cm on a single measurement (Jepsky, 1983). The PRAM III had an extremely high pulse rate of up to 4000 pulses per second. At 200 knots aircraft speed a data point about every 2.5 centimetres is processed. The unit was light portable and low in power. Using a gallium arsenide diode its transmitter was eye safe at the exit optics. Computer control was by microprocessor and a highly sensitive silicon avalanche diode was employed in the receiver.


The basic, high repetition rate PRAM III unit has been coupled with inertial systems such as Honeywell, Ferranti and the Litton Autosurveyor. When installed in helicopters these hybrid systems have many attributes permitting a wide range of applications for engineering and large scale mapping applications. They have been used in Tasmania and Queensland for route investigations and transmission line surveys (Blair and McLellan, 1984). But not for small scale mapping in Australia.


Despite the advantages of the high repetition, low power, Gallium Arsenide laser, the maximum range to ground in a standard clear atmosphere is less than 1000 metres. In normal dusty atmospheric conditions the operational maximum level was likely to be much less, probably under 500 metres. Experience with radar profiling and the WREMAPS I and II system had shown in Australia that in heat and turbulence the isobaric surface was not stable enough below 2000 metres to use as a height reference.


System Design


The AUSLIG LAPS system was designed to produce a height accuracy of 2 to 3 metres from a flying height of 10 000 ft.


To meet the operational mapping requirements it was decided to purchase a PRAM III system but to replace the Gallium Arsenide laser with a more powerful YAG pulsed laser similar to that used in WREMAPS II.


A Model NT-90 Rugged Compact, Nd:YAG laser system was supplied by International Laser System from Florida USA. The model NT-90 core unit was designed for multipurpose use on tripod, shipboard, vehicle or airborne mounts in adverse environmental conditions. Output range to a target was in excess of 20 kilometres. It incorporates a closed-cycle liquid to air heat exchanger. A high capacity, low noise fan is used in the heat exchanger to reduce acoustic noise level. The front end of the PRAM III module is supported by an Intel 86/05 single board, 16 bit microprocessor. It performs all mathematical calculations, diagnostics, range gating, range conversions and computer to computer output interfaces. The onboard data logger computer initially used was Hewlett Packard 85 model.


In addition to the PRAM III module incorporating the YAG laser and the data logger computer supplier by ACCI, other hardware, software and the electronics for system integration was provided by the electronic workshop in the Dandenong offce. This included:


·             70 mm strip camera (from WREMAPS I)

·             Barometric Reference Unit (from WREMAPS I)

·             Time reference

·             Electronic interface


After some problems were encountered in the initial production operations in Queensland the system was upgraded to include the following:


·             David Digital Elevation Computer (replaced the BRU) .

·             Computer Buffer for data logging system (128k)

·             NEC APC IV Powermate I Personal Computer with 1.2 Mbyte and 0.7 Mbyte floppy disk storage (replaced HP85)



System Specifications





50mJ Nd:YAG Laser

Pulse energy       

50 mJoules

Pulse width   

18 nsec

Beam divergence              

0.4 mRadians

Beam width at source




Ground pulse width from 10 000 ft flight level      

1.2 metres

Repetition rate                  

5/20 pulses per second



Strip Camera


Focal length               




Capacity per cassette        


Total number of cassettes


Each cassette is equivalent to 710 km @ 9 000 ft above terrain @ 360 kms per hour ground speed



Disk Storage


File length limited to 1.2 Mbyte, maximum line length at 20pps limited to approximately two hours continuous operation in the aircraft. In practice the lower pulse rate option is used away from intersection or ground control points.




Aircraft requirements


24-28 volts, 15-20 Amps


Total LTP system weighs 130 kgs


Currently the laser and strip film camera use the optical flat camera port of the Cessna 421C designed for an RC10 camera. The diameter of this hole is 50 cm. For mounting in other configurations separate holes of about 20 cm diameter for the laser and the strip camera could be used.


Data Acquisition


In operation the PRAM module measures the time interval between laser pulse transmission and reflected ground returns to provide ranging information in electronic and visual form in an LED display. An electromechanical shutter mounted on the transmitter assembly is controlled by the operator from the electronic console. The shutter is spring loaded so that it automatically closes unless maintained open by power through the operator control. A time reference is used to correlate system ranging data with the Digital Elevation Computer and to generate the flashing of a binary time code onto the strip camera. A marker indicating every 20th pulse is also shown on the film. Information from the Digital Elevation Computer is logged every second of time and each laser pulse return is individually logged. The file length in the NEC personal computer is limited to 1.2 Mbytes permitting a maximum profiling length at 20 pps of about two hours continuous operation before it is necessary to download data.


In early 1989 aircraft navigation is still by visual techniques using an NFK3 driftsight with aerial photography and Landsat imagery. Vertical control for each 1:250 000 map sheet usually consists of 6 or 7 N/S profiles and two E/W profiles, one at the top and bottom of each area.


Where possible flight lines are adjusted to pass over existing bench marks. Output from the profiling, apart from the real time LED display on the PRAM module, is fully digital.


Data Reductions


The validation and calculation of profiles along individual flight lines is carried out on a NEC Powermate 1 personal computer with the aid of a Houston 8011 digitising tablet and a Hewlett Packard Quietjet Printer.


Verification and initial processing of data is carried out in the field. Personal computer software has been compiled in Turbo Pascal to capture (DATCAP), verify (V-STRIP) and adjust the profile data generated by the Laser Profiler and the Digital Elevation Meter. At present the least squares adjustment of the network intersections and fit to all ground control is carried out on a VAX 11/750. Using the strip film, selected points are stereoscopically transferred onto the mapping photography for observation in the aerotriangulation process.


Australian Profiling Operations


Profiling largely depends on a number of factors such as weather, aircraft operational constraints, profile configuration, vegetation, and type of country. System accuracies are affected by slope of the terrain, foliage reflectance of the ground, turbulence, instability in the isobaric surface.


In 1987/88 two projects were undertaken as part of the 1:100 000 map revision program, upgrading the original radar profiles flown twenty years ago. The first was a block of three map sheets, Mount Coolon, Mackay, St Lawrence, and the second a block of six map sheets from Springsure to Roma. In this profile survey 7500 Km of line were flown over a period of five weeks. On one good day 1500 Km were flown during a 6 hour period. On this work the Cessna 421C operated at a ground speed of 360 Km per hour at an altitude of 3000 metres.


A least squares adjustment program (LASADZ) was used to adjust the laser network. This incorporates an interactive solution which employs robust estimations and gross error detection (DANISH). The final adjustment for the southern block of six sheets was run on 10 October 1988. The maximum residual in ground control was +2.9 metres at benchmark BL20 on line 3VI and the maximum residual in line intersections was +2.4m at the intersection of 15JI and 5VI. The results were assessed as having a height accuracy of 2 to 3 metres, sufficient for 10 and 20 metre contouring for the analytical aerotriangulation block.


Indonesian Operations


AUSLIG is currently involved in contracting the use of the LAPS to the private Canadian firm McElhanney Group Ltd. for profiling work in Indonesia. The mapping work in Indonesia is part of the Resource Evaluation and Aerial Photography project (REAP) began in 1978 under a loan agreement between the Governments of Canada and Indonesia. In 1987 the loan agreement was amended to convert the remaining amount of the agreement to grant funding. The purpose of the project was to provide basic materials and data to allow the Indonesian government to properly and accurately evaluate, assess and plan the development of their natural resources on the islands of Java. Sulawesi, Kalimantan, Bali, Madura, and the Nusatenggaras through the establishment of ground control, the production of aerial photographs and the provision of necessary tools, technical assistance and training and techniques.


The project was divided into three phases: (I) the establishment of horizontal ground control; (II) the acquisition of mapping quality aerial photographs; and (III) the development of and the provision of vertical control data, aerial triangulation and numerical adjustments to allow the production of accurate and sufficiently detailed topographic maps to meet the resource development needs of the Republic of Indonesia.


Prior to 1986 the first two components of the project were completed, leaving the third component to be carried out over the Islands of Kalimantan and Sulawesi. McElhanney Geosurveys Ltd. will carry out Phase III in 1989 which is the object of the present contract.


It is expected Phase III of the project will permit the Government of Indonesia to implement a loan supported project, to finalise the mapping process and produce the products needed as planning and development tools for these regions.


Part of this last phase of the project is to provide vertical control by using Airborne Profile Recording (APR) techniques and to perform the aerial triangulation and numerical adjustments of certain portions of the Islands of Kalimantan and Sulawesi and at the same time to provide a proper transfer of technology on the operations performed.


Bakosurtanal will act for the Indonesian government in the supply of material and administrative arrangements. AUSLIG will supply the laser profiler and technical support for the equipment, which will be installed in aircraft in Indonesia.


Beyond the Horizon


The strength of the LAPS is in its application to provide extensive vertical control for small scale photogrammetric stereoplotting. It is not a multi-purpose system such as are available for laser profilers linked to inertial systems in helicopters. Design accuracy at present is a system accuracy of 2 to 3 metres. Current weaknesses of the system are the reliance on visual driftsight navigation techniques and the necessity for obtaining x and y positioning where required from photogrammetric techniques from a strip camera. As such it has limited use for accurate, real time positioning as required for linear surveys such as transmission lines. A secondary disadvantage is the need to rely on a stable isobaric surface as a vertical reference between the overflight of control points. Both these disadvantages are expected to be overcome in the near future by the use of Kinemetic GPS technology. But the very success of this approach may also reduce the need for vertical control for small scale photogrammetry plotting if the GPS can be successfully employed in the aerial photography aircraft at the time of photography.


In the short term at least the LAPS provides an efficient method of providing vertical control for mapping in remote or inaccessible areas.






BLAIR J.D. and McLELLAN J.F. (1984) 'Route Profiling in Queensland Using Satellite Control and an Integrated Inertial and Laser Profiling System', in The Australian Surveyor Vol 32 No 4 pp 257-273


JEPSKY, J. (1983) 'A Microprocessor Controlled Airborne Laser Profiling and Mapping System', in Proceedings of American Society of Photogrammetry (ASP-ACSM) Full Technical Meeting, September Salt Lake City


MANNING, J. and MENZIES R. (1988) 'Vertical Control for Australian Topographic Mapping', in Proceedings of 30th Australian Survey Congress Sydney



The AUSLIG laser airborne profiling system / J. Manning, AUSLIG. – In Technical Papers, Australian Survey Congress (3 1st : 1989 : Hobart) and in National Surveying Conference (1st : 1989 : Hobart), 1-9. – 3 refs.