Probabilistic road classification in historical maps using synthetic data and deep learning

Dominik J. Mühlematter, Sebastian Schweizer, Chenjing Jiao, Xue Xia, Magnus Heitzler, Lorenz Hurni - 2024

In correspondence with the code we released on GitHub, the usage of the models within our pipeline is described in the repository. Please note that this repository contains only the models for our final results, not for all intermediate results.

Abstract

Historical maps are invaluable for analyzing long-term changes in transportation and spatial development, offering a rich source of data for evolutionary studies. However, digitizing and classifying road networks from these maps is often prohibitively expensive and time-consuming, limiting their widespread use. Recent advancements in deep learning have made automatic road extraction from historical maps feasible, yet these methods typically require large amounts of expensive labeled training data. To address this challenge, we introduce a novel framework that integrates deep learning with geoinformation, computer-based painting, and image processing methodologies. This framework enables the extraction and classification of roads from historical maps using only road geometries without needing road class labels for training. The process begins with cascaded training of a binary segmentation model to extract road geometries, followed by morphological operations, skeletonization, vectorization, and filtering algorithms. Synthetic training data is then generated by a painting function that artificially re-paints road segments using predefined symbology for road classes. Using this synthetic data, a deep ensemble is trained to generate pixel-wise probabilities for road classes to mitigate distribution shift. These predictions are then discretized along the extracted road geometries. Subsequently, further processing is employed to classify entire roads, enabling the identification of potential changes in road classes and resulting in a labeled road class dataset. Our method achieved completeness and correctness scores of over 94% and 92%, respectively, for road class 2, the most prevalent class in the two Siegfried Map sheets from Switzerland used for testing. This research offers a powerful tool for urban planning and transportation decision-making by efficiently extracting and classifying roads from historical maps, and potentially even satellite images.

Citation

If you find our work useful or interesting, or if you use our code, please cite our paper as follows:

@misc{ProbRoadClass2024,  
  title   = {Probabilistic road classification in historical maps using synthetic data and deep learning},  
  author  = {Dominik J. Mühlematter, Sebastian Schweizer, Chenjing Jiao, Xue Xia, Magnus Heitzler, Lorenz Hurni},  
  year    = {2024},  
  note    = {arXiv:2410.02250}  
}

Pretraining

This folder contains the pretrained models, including:

ResNet18 Classification Backbone: Pretrained on ImageNet (For more details, see the PyTorch GitHub repository) .
Binary Road Segmentation Model: Initialized with the ImageNet classification backbone and trained using cascaded training with Swiss Map data.

Binary_road_segmentation

This folder contains the final model weights used for extracting roads from the Siegfried Map.

Road_classification_ensemble

This folder contains all the model weights for the final road classification ensemble trained on the Siegfried Map.