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AltGeoViz: Facilitating Accessible Geovisualization

Chu Li, Rock Yuren Pang, Ather Sharif, Arnavi Chheda-Kothary, Jeffrey Heer, Jon E. Froehlich

TL;DR

AltGeoViz addresses the accessibility gap in dynamic geovisualizations by auto-generating viewport-aligned alt-text that describes spatial patterns and descriptive statistics. The method uses a $3 \times 3$ grid to abstract map views, ranks grid cells, and conveys location-based patterns through concise natural-language summaries, while providing a keyboard-driven interaction model for screen-reader users. In a remote qualitative study with five participants, AltGeoViz enabled new exploratory capabilities and improved understanding of spatial data, though users highlighted navigation and comparability as areas for improvement. The work contributes an open-source system, empirical evidence of feasibility for screen-reader users, and directions for enhancements such as search, comparison across regions, and data-table integration, with implications for broader data-to-text approaches in geospatial visualization.

Abstract

Geovisualizations are powerful tools for exploratory spatial analysis, enabling sighted users to discern patterns, trends, and relationships within geographic data. However, these visual tools have remained largely inaccessible to screen-reader users. We present AltGeoViz, a new system we designed to facilitate geovisualization exploration for these users. AltGeoViz dynamically generates alt-text descriptions based on the user's current map view, providing summaries of spatial patterns and descriptive statistics. In a study of five screen-reader users, we found that AltGeoViz enabled them to interact with geovisualizations in previously infeasible ways. Participants demonstrated a clear understanding of data summaries and their location context, and they could synthesize spatial understandings of their explorations. Moreover, we identified key areas for improvement, such as the addition of intuitive spatial navigation controls and comparative analysis features.

AltGeoViz: Facilitating Accessible Geovisualization

TL;DR

AltGeoViz addresses the accessibility gap in dynamic geovisualizations by auto-generating viewport-aligned alt-text that describes spatial patterns and descriptive statistics. The method uses a grid to abstract map views, ranks grid cells, and conveys location-based patterns through concise natural-language summaries, while providing a keyboard-driven interaction model for screen-reader users. In a remote qualitative study with five participants, AltGeoViz enabled new exploratory capabilities and improved understanding of spatial data, though users highlighted navigation and comparability as areas for improvement. The work contributes an open-source system, empirical evidence of feasibility for screen-reader users, and directions for enhancements such as search, comparison across regions, and data-table integration, with implications for broader data-to-text approaches in geospatial visualization.

Abstract

Geovisualizations are powerful tools for exploratory spatial analysis, enabling sighted users to discern patterns, trends, and relationships within geographic data. However, these visual tools have remained largely inaccessible to screen-reader users. We present AltGeoViz, a new system we designed to facilitate geovisualization exploration for these users. AltGeoViz dynamically generates alt-text descriptions based on the user's current map view, providing summaries of spatial patterns and descriptive statistics. In a study of five screen-reader users, we found that AltGeoViz enabled them to interact with geovisualizations in previously infeasible ways. Participants demonstrated a clear understanding of data summaries and their location context, and they could synthesize spatial understandings of their explorations. Moreover, we identified key areas for improvement, such as the addition of intuitive spatial navigation controls and comparative analysis features.
Paper Structure (12 sections, 2 figures, 2 tables)

This paper contains 12 sections, 2 figures, 2 tables.

Table of Contents

  1. Introduction
  2. AltGeoViz Design and Implementation
  3. Summarizing Spatial Trends
  4. Alt-text Design
  5. Implementation
  6. User Evaluation
  7. Participants and Procedure
  8. Data and Analysis
  9. Findings
  10. Feedback on AltGeoViz
  11. Suggestions for Improvements
  12. Discussion and Conclusion

Figures (2)

  • Figure 1: Our grid-based abstraction method for summarizing geovisualization. (A) The bounding box is subdivided into a 3x3 grid. (B) Each polygon is assigned to the grid cell containing its centroid. (C) For each cell, the data values of all associated polygons are aggregated, and the mean value is calculated. Cells are then ranked from 1 (highest) to 9 (lowest).
  • Figure 2: Possible scenarios for adjacent cells in sequential ranking and their corresponding location indicators. Yellow for four, blue for three and green for two sequentially ranked adjacent cells.