Haumer, Nickel, Nollenburg and Wallinger – TOWARDS AUTOMATED MULTILEVEL SCHEMATIC MAPS 2022

Description

The paper introduces a formal model and algorithmic pipeline for automatic schematization of multilevel transit networks, extending single-level transit-map methods to hierarchical networks (two levels). Contributions include: a formal multilevel model, extended design criteria combining traditional octolinear rules (octolinearity, topology preservation, straightness, relative-position preservation, edge uniformity, station separation) with multilevel principles (network separation and network distortion), and a preliminary mixed-integer linear programming (MILP) approach to produce octolinear two-level maps. The pipeline planarizes and contracts subnetworks, augments them with external stations, computes individual MILP layouts with constraints enforcing external-station placement, derives octolinear convex hulls, then arranges and connects subnetworks via a second-level MILP before final post-processing. A case study on the Austrian commuter network produced a clear, draft-quality schematic in about four minutes using Gurobi. Limitations include MILP computational complexity and the non-overlap hierarchy assumption; open questions concern alternative faster methods, integrated models, labeling, user evaluation, and interactivity versus static maps.