An International Journal of Computini and Informatics Spatial Data

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Volume 23 Number 2 May 1999

ISSN 0350-559


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Figure 5: Worker Space-Time trajectory entering lOOK area at Hanford. The additional white arrows indicate the space-time 'flow' of the worker trajectory. There are some interesting features to note here:

space-time trajectory structure reflects this latter transition. In this vertical segment of the trajectory, we see the workers' first main shift of the day represented by the first segment of the trajectory (a 3-hour shift, item iii in Fig. E). The slight displacement to the right, half-way up the vertical stretch (item iv, Fig. E), indicates workers dressing down, going to lunch, and dressing up again ready for the afternoon shift (2 hours and 20 minutes). Note the stability of location in space during the main shifts of the day. Next, workers are debriefed and make their way to the parking lot and then to the entrance of lOOK.

— One can see the difFerence in time taken (vertical dimension of trajectory segment) to get from the Hanford entrance (ofl image, to the right) to the entrance of the lOOK area (Figure 5, item i), compared with the time taken to get from the lOOK entrance to the parking area (Figure 5, item ii). This is a good illustration of the logic structure operating in our implementation of Hagerstand's visual components using Hanford management infrastructure-based worker Information. We were provided only a generahzed account of Figure 6 (above) completesthe day's space-timetra: worker movements around the lOOK area. As a jectory for a worker, joining the lOOK area with the result of this, it was only possible to represent this Hanford entrance along the previously traveled route. in terms of time spent by a worker in a given route Note the spatial (x, y, z) relationship between the ensegment or building based on typical time taken to try space-time trajectory segment (lower) and the decomplete the entire task at/in that location. This parture space-time trajectory segment (upper). This explains the abrupt transitions between adjacent illustrates the problem of using the same path in space space-time trajectory segments. in two or more different time periods discussed earUer. — Along the left edge of the image, we see the main Up until this point, we have shown the construction portions of a worker's day. From the parking lot of the workers' space-time trajectory. The images in (the right-hand green area), the workers follow figures E and F begin to demonstrate the power of the magenta surface route to the 105KE building, adopting the space-time representation in identifying via ofRces and dressing area. The thick trajectory the spatio-temporal relationship between workers and segment that joins with the bottom of the vertical potential exposure to hazardous material.

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Informatica 23 (1999) 155-168

N. R. Hedley et al.

Figure 6; Complete Space-Time Trajectory for one worker). The fifth image (Figure 7, above left) shows the addition of the space-time trajectory of the 105KE building, where workers spent most of their working day. Notice that the worker trajectory remains vvithin the 105KE trajectory volume for a lengthy period. This represents the workers' vulnerabiUty to hazard exposure for this duration. The next image (Figure 8, above right) does not represent the trajectory of 105KE (though it is stili there). The green volume represents the space-time trajectory of the spent nuclear fuel handling room vvithin the 105KE building. However, notice that examination of the intersection of the worker trajectory and the handling room trajectory reveals that more of the worker time is spent in the handling room than is spent in the 105KE building alone. We know that worker vulnerability to hazard exposure is greater in this area than in the generai 105KE building. This visualization approach is useful to express this difference. Combining radiological dose for this particular building and area with space-time Information allows us to observe space-time intersections of workers with areas of different radiological exposure within the same building. This can be seen in Figure 9 (above). The space-time

trajectory of workers passes through the 105KE building, but while inside, it also passes through the spent nuclear fuel handling room. This is a highly significant application for determining cumulative worker exposure, and understanding the space-time composition of that exposure. Finally, Figure 10 (above) visualization work provides a sense of the relative proportions of the space-time trajectory for workers at the lOOK area with respect to the larger Hanford landscape.

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Discussion

Visualization in 3D GIS The images shown in this paper do not do justice to the real environment in which this space-time visualization has been conducted. Using the mouse, a user may freely navigate through ali environments shown in these images, viewing them from any angle. We suspect that the ability to manipulate rotation about three axes is more powerful for Information exchange than previous static, perspective, non-3D space-time depictions. The ability to interactively switch themes (essentially objects) in the view on and off allows focused subsets of data to be viewed and minimizes occlusion difEculties. This is

Informatica 23 (1999) 155-168

HAGERSTRAND REVISITED: INTERACTIVE

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