Abstract
Recent advances have enabled the extraction of vectorized features from
digital historical maps. To fully leverage this information, however, the
extracted features must be organized in a structured and meaningful way that
supports efficient access and use. One promising approach is question answering
(QA), which allows users -- especially those unfamiliar with database query
languages -- to retrieve knowledge in a natural and intuitive manner. In this
project, we developed a GeoQA system by integrating a spatio-temporal knowledge
graph (KG) constructed from historical map data with large language models
(LLMs). Specifically, we have defined the ontology to guide the construction of
the spatio-temporal KG and investigated workflows of two different types of
GeoQA: factual and descriptive. Additional data sources, such as historical map
images and internet search results, are incorporated into our framework to
provide extra context for descriptive GeoQA. Evaluation results demonstrate
that the system can generate answers with a high delivery rate and a high
semantic accuracy. To make the framework accessible, we further developed a web
application that supports interactive querying and visualization.
University of Southern California
Abstract
Spatial representation learning is essential for GeoAI applications such as
urban analytics, enabling the encoding of shapes, locations, and spatial
relationships (topological and distance-based) of geo-entities like points,
polylines, and polygons. Existing methods either target a single geo-entity
type or, like Poly2Vec, decompose entities into simpler components to enable
Fourier transformation, introducing high computational cost. Moreover, since
the transformed space lacks geometric alignment, these methods rely on uniform,
non-adaptive sampling, which blurs fine-grained features like edges and
boundaries. To address these limitations, we introduce Geo2Vec, a novel method
inspired by signed distance fields (SDF) that operates directly in the original
space. Geo2Vec adaptively samples points and encodes their signed distances
(positive outside, negative inside), capturing geometry without decomposition.
A neural network trained to approximate the SDF produces compact,
geometry-aware, and unified representations for all geo-entity types.
Additionally, we propose a rotation-invariant positional encoding to model
high-frequency spatial variations and construct a structured and robust
embedding space for downstream GeoAI models. Empirical results show that
Geo2Vec consistently outperforms existing methods in representing shape and
location, capturing topological and distance relationships, and achieving
greater efficiency in real-world GeoAI applications. Code and Data can be found
at: https://github.com/chuchen2017/GeoNeuralRepresentation.