The paper is explicitly marked as "Preprint. Work in progress," indicating it has not yet undergone formal peer review, which is a crucial step for scientific validation.
Reliance on Image Retrieval
FastForward's strong performance, particularly its accuracy, heavily relies on a prior image retrieval step to select relevant mapping images. Without this step (e.g., random sampling of mapping images), the accuracy significantly drops, making it less robust in scenarios without pre-computed retrieval.
Computational Cost of Global Descriptors
While the retrieval index is fast to build, the time to extract global descriptors for a growing number of images is not negligible, which can still add to overall mapping overhead for very large datasets.
The PnP-RANSAC pose solver, while standard, is currently the most time-consuming step in FastForward's localization process, taking up to 2.2 seconds on average in some scenes, indicating room for further optimization for truly real-time applications.
Scale Normalization Dependency
While the scale normalization strategy improves generalization, FastForward's accuracy can still be significantly affected without it, especially in large-scale outdoor scenes not explicitly covered during training.