Speed-Dependent Automatic Zooming (SDAZ) is a new and promising method of scrolling that has already been shown to be superior to scrollbars in performing some tasks. We have analysed the different forms of document navigation and identified the place of SDAZ within the existing framework of navigation techniques, showing it to be complementary to the more traditional methods, but a replacement for rate-based scrolling.

The implementation of SDAZ requires making a number of design decisions in the interface and the selection of control formulae. The extent of the difficulty of this is not made clear in the previous literature, nor have the decisions made in the previous implementations been explained fully. The main part of our work here has been to explore this problem of calibration. We offer a complete survey of the issues we discovered in the calibration of an SDAZ system, and through an iterative development of the system through informal user feedback we have attempted to obtain an optimal SDAZ implementation and have reported the details here.

Finally we conducted a small experiment with the primary intention of comparing SDAZ to rate-based scrolling. We found that SDAZ was 13\% faster that rate-based scrolling and preferred by most participants. This validates the hypothesis that the addition of zooming to rate-based scrolling is beneficial.

\section*{Future Work}

Many areas for future work were discussed extensively in Chapter 4. Those areas in particular that we would like to see future work done will be mentioned briefly here.

After performing our evaluation we do not feel that our control equations are optimal. We now believe (in agreement with \citename{ih:1}) that an exponential based mapping between mouse displacement a scroll speed, with a linear mapping between scroll speed and magnification would be optimal. For the sake of simplicity we arbitrarily excluded non-linear mappings between displacement and scroll speed from our consideration early in our investigation and we now believe it would be worthwhile to examine them.

The problem of stopping and reversing the scrolling direction occurred repeatedly. We have suggested that it would be useful if users could just jerk the mouse in the opposite direction they are currently travelling, the system would respond by bringing them instantly to a complete halt. (See Section \ref{calStoppingInstantly} for a detailed discussion of this problem.)

Our evaluation suggested that we needed to reconsider the maximum zoom level. We had arbitrarily decided on a maximum magnification of 10 pages, which we personally found to be too low, but other users found to be too high. Perhaps improved control equations with a higher maximum magnification would solve this problem.

The decision also needs to be made as to whether users can be presented with a ``one size fits all'' system, or whether it is best to offer users the ability to customise the system. In the latter case, it would be necessary to decide upon what the customisable options should be.
