DIAGRAMA DE FLUJO DE BÚSQUEDA Y SELECCIÓN

The way in which data layers were presented was an issue brought up in a number of cases by many participants. The Landcover Chart was generally considered useful by the participants (Figure 5.1), but some also suggested that additional usefulness could be gained by having the land cover data available as a map layer. This would be in addition to the available layer that displays the vegetation class. The colour gradients used for the solar layers and the surface temperature layers was confusing to some users (Q1, Q2). Questionnaire responses as well as in-person discussion pointed to the confusion of the two

data sets using the same colour gradient, making it unclear in some cases how they were different.

Q1: Appealing presentation – some confusion between temperature and solar.  Q2: [The] colour ramp resembles heat readings. 

The discussion concluded that a component of this issue was how the solar data closely correlates with sunlight hours and shaded areas, making it visually comparable to “hot and cold” areas. One participant suggested that without temperature readings, some of the “hot spots” may imply to a user that it is an unsafe or vulnerable area (Q3). Perceptions and bias can lead users to develop a false understanding of results. Preventing a user from thinking that a red or “hot” area is inherently negative is important when developing maps (Campbell, 2001). One option to resolve this would be to include “tooltips” that displayed surface temperature or solar radiation at an area when the mouse hovered over it.

Q3: Good for a general understanding of heat vs. land use, but people may think they  are vulnerable in a hot spot. 

  Figure 5.1: Rankings of usefulness of Landcover Chart

0 1 2 3 4 5 6 7

Not Helpful Little Help Neutral Somewhat

Helpful Very Helpful #  of  Users

Q2: Usefulness of Land Cover Chart Tool

Surface Temperature Data Visualisation

Participants generally considered the surface temperature datasets to be useful both for their own use and for public use in understanding the link between environmental issues and surface temperature (Figure 5.2). Participants found the data useful for understanding heat issues and being able to quickly compare temperature with land cover and aerial imagery. One participant commented that the tool was particularly useful for zooming in on unusually “hot” or “cold” areas on the map and investigating what the cause may be.

  Figure 5.2: Rankings of usefulness of surface temperature data

A significant question posed to the participants was about the usefulness of the two available surface temperature visualisation techniques. When participants were asked to choose which was more useful, the responses were split. Some participants argued that the degrees above or below the daily mean option was useful once it had been properly described in-person as the legend was insufficient (Q4, Q5). One participant wrote that it “...provided a foundation for a stronger rhetorical argument...” as it allowed different dates to be compared in a more objective manner. Other participants preferred the surface temperature values method as it was an easier concept to understand. One response articulated that the public is not interested

0 1 2 3 4 5

Not Helpful Little Help Neutral Somewhat

Helpful Very Helpful #  of  Users Participant's Use Aid public understanding

Q4: Usefulness of Surface Temperature Data

in standard deviations of temperature (Q6). Another response pointed out that the difference from daily mean was not intuitive and required an explanation. Speaking about both methods, one participant suggested the option to display either the raw, non-interpolated surface temperature rasters or the existing interpolated rasters that had smoother transitions between cells. In one instance a participant was unclear on how the thermal data was derived, wondering if each available time was a time-dimensionless snapshot or an average of multiple points in time.

Q4:  [Degrees  from  the  mean]  needs  to  be  described  and  explained  before  it  can  be  understood. 

Q5:  [Degrees  from  the  mean]  is  helpful  once  the  legend  [and  standard  deviation]  is  explained. 

Q6: [The] public does not care about standard deviation. 

This feedback touches on the challenge that exists with dynamic mapping as the author no longer has as careful control over the look and contents of the map (Morrison, 1997). New capabilities such as transparency levels, altering colour gradients or even, in this case, altering the visualisation format of a layer can be useful, if the challenge of over-complexity can be overcome (Kraak, 2004).

Land Cover-Surface Temperature Relationship

A large component of the script and questionnaire was centred on investigating how participants used the Landcover Chart tool and surface temperature data together. Participants identified that using these tools in combination was generally useful at investigating the relationship between surface temperature and land cover in the study area (Figure 5.3). One response commented on the usefulness of being able to quickly “cross- reference” land cover with surface temperature by using the Landcover Chart in conjunction

with the surface temperature layers. One participant commented that the differences in resolution between the land cover data and surface temperature layers was insufficient for investigating these linkages at a larger scale (Q7). Other participants commented on the lack of discrete temperature values or a way to query these values in the mapped layers outside of the Thermal Transect tool. Another participant suggested that it may be ideal to display individual temperature values in some manner on the map along with the rasters. This was considered as a potential option but was not implemented due to the large number of values that would have to be displayed.

Q7: The differences in resolution can not give us the detail we are looking for. 

  Figure 5.3: Rankings of usefulness of Landcover Chart and temperature data

The Thermal Transect tool was also generally seen as being useful for personal use as well as aiding the public’s understanding of surface temperature’s link with environmental issues (Figure 5.4). Participants found it useful to investigate how the temperature changed along walking or driving routes. The tool was also informally used in some cases to understand how much the temperature changed between different features seen on the aerial imagery as well as different land cover types. A common suggestion was to include additional data that

0 1 2 3 4 5

Not Helpful Little Help Neutral Somewhat

Helpful Very Helpful #  of  Users

Q5: Usefulness of Land Cover Chart combined 

with Surface Temperature Data

would increase the usefulness of the surface temperature data and the Thermal Transect tool; some suggestions included air quality data layers and traffic data (Q8).

Q8: I think it would be great for planners and public health workers (an air quality or  traffic flow layer would be great!” 

One group of participants suggested that it would be very useful to include network analysis functionality in order to create pedestrian routes that consider surface temperature as a factor when routing. This was also considered during the development process but was not done as it was outside of the scope of the tool due to the amount of time available.

  Figure 5.4 – Rankings of usefulness of Thermal Transect