[Nomad FR]: Consistent, effective map symbology

[Den-Boychuk]

Contact Details

GitHub @Den-Boychuk

What is needed?

Recommendations

• Consistent symbology should be used because it helps experienced users interpret maps quickly and consistently
• Outside Nomad, the same people will use FireSTARR-WMS and Nomad maps, so matching all symbology is ideal: categories, colours, and raster vs vector
• Because FireSTARR-WMS is Canada-wide and agencies share personnel, custom, agency-specific symbology should be discouraged
• Within Nomad, users should be unable to shift probability categories or colours
• Because (1) Nomad can import and display the FireSTARR-WMS layer and (2) the FireSTARR-WMS provider can change the symbology at any time, the FireSTARR-WMS legend should be downloaded from the FireSTARR WMS (...request=GetLegendGraphic...) along with the map
  • The ability of the FireSTARR-WMS provider to change symbology at any time unfortunately makes it harder to maintain consistent symbology with Nomad
  • Significant symbology changes in-season, however, are fortunately unlikely
• (This may connect with closed issue #152)

Background information, rationale, and details for colours and categories

• Symbology (categories, colours, transparencies, patterns) should convey operationally important information quickly and accurately
  • Colour conveys the level of alarm, while considering colour blindness
  • (See https://doi.org/10.3390/fire4030050 about visualizing wildfire data)
• FireSTARR symbology was operationally evaluated and periodically refined (but see below*)

Caption: An older FireSTARR-in-Ontario (“FireGUARD”) burn probability map

Caption: firestarr_probability_processing_7pct

• The “Existing” colour is to distinguish the existing burned area from the highest probability
• The “Unprocessed” and “Processing” colours seem irrelevant for Nomad, but they are relevant for imported FireSTARR-WMS
• It’s knowingly hard to identify on maps the exact probability categories by colour because most adjacent colours are similar
  • The intention is to convey the level-of-alarm gradient over large areas
  • The absence of distinct probability categories (except for the blue--see below*) and boundaries, e.g., Low, Moderate, High, Extreme, is deliberate
  • The exact numerical probability category of each ha shouldn’t be considered operationally relevant, because (1) fire growth models are not that accurate, and (2) fire response decision-making is expertise-based, not quantitative (this may be debatable)

Caption: FireSTARR-WMS burn probability map

Background information and rationale for 1-ha resolution of mapping

• The rationale is outlined in section “Spatial extent and resolution” of the FireSTARR-in-Ontario (“FireGUARD”) paper https://doi.org/10.5558/tfc2025-015
• The pros for converting FireSTARR’s raster output to polygons are unclear; the cons are alteration of the source raster data and symbology inconsistency with FireSTARR-WMS

Caption: Nomad pre-MVP polygon format

Caption: Nomad pre-MVP raster format

*Past and future changes to colours and boundaries

• This is only FYI and for possible discussion
• The current symbology is arguably not final, e.g., using blue for 0-10% probability is problematic:
  • It can be hard to distinguish from lakes, especially on low-quality monitors
  • It interacts poorly with greens etc on basemaps, especially with transparency
  • An operational person said, “I want blue for the parts I don’t have to worry about”, but people need to worry about 0-10% and also beyond 0%, because all models have false negatives
  • An earlier symbology deliberately faded out the 0% boundary to help prevent the mistaken belief that the modelled boundary reliably shows the spatial hazard limit

How will this improve the project or tool?

Consistent symbology helps experienced users interpret maps quickly and consistently.