...

2. If there exists no data for the stroke rate/split we grayed out the "Plot" button and replaced the numbers with "- " or "-- : --" respectively. Users found this to be very intuitive and never confused that feedback with lost data (usually it meant their accelerometer or GPS were turned off).

...

Luckily, we chose to develop our app for iOS deployment. Apple provides a very nice set of UI elements that are standard and used commonly in most apps. This meant that most of our implementation involved dynamic data logging and displaying instead of trying to reinvent UI for the iPhone. Below are listed the two parts of our implementation that went beyond the UI and impacted some of our design decisions.

...

Our plotting is currently very simple; it simply shows a line graph of the saved split and stroke points. We decided to focus our efforts on the race view UI and ignore the plotting UI, so you cannot compare pieces of data or show a plot while viewing other pieces of data. This is because our tasks focused on the race view and playback, not on quantitative data analysis.

...

Navigating

...

We spent considerable effort in this phase of development considering the specific actions each upper navigation button would take, as this is the most fundamental way the user navigates through the application.  Changing such simple things as the wording of a button or whether the button appears by default came to have  large effects on the usability and learnability of our application. Additionally, enabling text fields to be saved either using the Done button in the native keyboard or using the confirm button in the upper navigation bar helped new users complete the edit they had set out to make without a second thought.

...

Implementation Problems

...

As the iOS standard user interface elements are few, well-known, and well-documented, we had a concrete idea of the interface capabilities at the outset of our implementation.  Few major problems with the interface eluded us, and overall there were no shortcomings in the interface that significantly change the users' experience with our application.  Small issues such as the difficulties in rendering graphs or dynamically replaying the acceleration data are not major problems, and do not affect the interface's usability.

Evaluation

Our 3 users were two MIT rowers and one coxswain. One of our team members knew them from rowing in a past year. Thus our users were very representative of our user population. Each of the users were comfortable with iOS, so we didn't need to introduce them to the UI that a regular iPhone user should know. We gave them the following briefing and tasks:

...