Plotters at the scene of a crime

The Guardian (Manchester); 14 March 1991; Claire Neesham; p. 33

THE aftermath of a traffic accident on a foggy morning in Leeds is not the obvious place to find a bunch of computer people demonstrating the potential of their hardware and software. But on February 27, any passer-by on Bellevue Road, Leeds would have seen exactly that. This was the day the West Yorkshire Police began time trials on a number of digital plan-drawing techniques. The aim was to compare the performance of the systems in a simulated situation: in this case, two cars colliding at a T-junction. Raymond Petre, West Yorkshire's scientific support manager, says the police force is interested in digital techniques as a way to increase the speed, accuracy and presentation quality of maps and plans. Today, recording an accident like the one simulated involves using a tape measure to identify the position of significant objects, jotting this data in a notebook and drawing a rough sketch. The final plan is then produced with pen and paper back at the office. It's a lengthy process and the results are not always ideal. An additional problem, says Petre, is that viewing black and white line drawings can be off-putting for a non-technical juror in court. It would be better to use a computer aided design system such as AutoCad to produce well-annotated colour plans. These could also help to speed up the process if linked into a digital data collection system. Petre and his team have been awarded a Police Requirement Support Unit Research Grant by the Home Office to look into options for improving data collection and plan drawing. This goes beyond vehicle accident sites to, for example, murder inquiries and piecing together evidence after a disaster. The results will be made available to other police forces both nationally and internationally. So far they have identified a number of computer-aided drafting (CAD) and data collection packages for further evaluation. Among the data collection systems is a package which uses GRiD Computer Systems' GridPad a stylus operated, hand-held computer. The GridPad is connected via a serial port to a Carl Zeiss Surveying Elta 6 Total Station a combined electronic theodolite and range-finder capable of identifying the angle and distance of an object from a fixed position. This is controlled by the graphics-based data collection software written for the GridPad by Richard Trainer of Tangent Technology Design. The GridPad's attraction is that users do not need keyboard skills. All data entry into the tablet, which is about the same weight and size as a telephone directory, is made with a pen-like stylus. This is used to write on the touch-sensitive LCD screen, which is almost the same size as the GridPad. GRiD supplies the PC-compatible machine with MS DOS, a windowing environment, and algorithms for block capital and number recognition. Trainer's application makes use of the GridPad's 640-by-400 resolution graphics capabilities by representing data, as it is collected, as a map with symbols showing the position of various objects. Symbols for particular tasks can be predefined using GRiD's icon drawing software on a PC. So for traffic accident work, the GridPad's on-screen menus could hold icons for cars, pieces of vehicle, bodies and street furniture. These could then be placed at the appropriate positions on the drawn map. Alternatively, different categories of objects can be identified by letters. All this data can then be stored in the GridPad database along with details of who found what part. Petre says that the facility to draw maps on-site was vital in selecting the GridPad for trials. ``It is easier to check the data being recorded and ensure that all the points are connected in the right order if you can watch the plan emerging on the GridPad.'' Trainer came up with the idea of providing a way to visualise data collected when he developed the original version of the software Tangent Survey System for archaeologists, who mainly use the system with the Total Station. Trainer has developed his software so that the Total Station can be controlled from the GridPad. Also, all graphical data is stored in a standard DXF format, which is easy to transfer to a CAD package via a serial port (the GridPad uses two removable memory cards rather than floppy discs). With the next version of his software, due for release on April 2, Trainer is aiming to broaden the package's appeal. The new software also includes a level of data protection by preventing users from erasing data: if they make a mistake they can mark the error, but the original data can't be removed. There is also the facility to load digital Ordnance Survey maps into the GridPad and use them as the basis for maps or plans. This new version also includes support for a wider variety of surveying techniques, including traditional tape and wheel methods. This is attracting attention from both commercial survey firms and the police. Petre included it in his evaluation of building survey tools. There is, however, no guarantee that the GridPad will become police standard issue. At the February trials, a number of other techniques were also being investigated. For example, photogrammetry where very accurate photographs of the accident scene are taken and the data transferred to a plan can provide fast data collection. What will determine which systems win the police stamp of approval is how much time they save. After a major motorway accident or air crash, plans must be produced quickly and the debris, evidence and vehicles removed to reduce disruption. In the Bellevue Road case, of course, passers-by were surprised to see that the cars remained strewn across the road for two days. . .

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