Black-and-white draft geological maps, produced during fieldwork, often contain dense handwritten annotations overlaid on monochromatic contour basemaps. Although interpretable in grayscale, the lack of color makes it difficult to visually distinguish overlapping or adjacent geological units, especially when boundaries are unclear and annotation styles vary. However, colorizing these draft maps is labor-intensive but essential, as they may be the only source of detailed geological information for certain regions. This hinders both human interpretation and downstream tasks such as map digitization and critical mineral resource assessment. We target the problem of automated colorization of draft geological maps. The challenge lies in interpreting noisy visual cues from uncolored sketches and assigning appropriate colors according to their geological categories. We propose a novel machine learning approach that exploits polygon metadata, including map keys that explicitly define geological units and implicitly suggest their intended colors, along with the semantic interpretation of the sketch content in the maps, to assign colors to the draft maps accordingly. We evaluate our method on USGS draft geological maps; it outperforms comparative methods by 15.7%. In addition, our approach improves downstream polygon-extraction performance by 9% in F1 score.

Locating undiscovered deposits of critical minerals requires accurate geological data. However, most of the 100,000 historical geological maps of the United States Geological Survey (USGS) are in raster format. This hinders critical mineral assessment. We target the problem of extracting geological features represented as polygons from raster maps. We exploit the polygon metadata that provides information on the geological features, such as the map keys indicating how the polygon features are represented, to extract the features. We present a metadata-driven machine-learning approach that encodes the raster map and map key into a series of bitmaps and uses a convolutional model to learn to recognize the polygon features. We evaluated our approach on USGS geological maps; our approach achieves a median F1 score of 0.809 and outperforms state-of-the-art methods by 4.52%.

Historical maps contain detailed geographic information difficult to find elsewhere covering long-periods of time (e.g., 125 years for the historical topographic maps in the US). However, these maps typically exist as scanned images without searchable metadata. Existing approaches making historical maps searchable rely on tedious manual work (including crowd-sourcing) to generate the metadata (e.g., geolocations and keywords). Optical character recognition (OCR) software could alleviate the required manual work, but the recognition results are individual words instead of location phrases (e.g., "Black'' and "Mountain'' vs. "Black Mountain''). This paper presents an end-to-end approach to address the real-world problem of finding and indexing historical map images. This approach automatically processes historical map images to extract their text content and generates a set of metadata that is linked to large external geospatial knowledge bases. The linked metadata in the RDF (Resource Description Framework) format support complex queries for finding and indexing historical maps, such as retrieving all historical maps covering mountain peaks higher than 1,000 meters in California. We have implemented the approach in a system called mapKurator. We have evaluated mapKurator using historical maps from several sources with various map styles, scales, and coverage. Our results show significant improvement over the state-of-the-art methods. The code has been made publicly available as modules of the Kartta Labs project at https://github.com/kartta-labs/Project.