Ensar at GroundLM 2026 Shared Tasks: Symbolic Scene Serialisation for View-Level Evidence Identification

Mostafa Gaafar, Omar Mokhtar Gaber Saqr


Abstract
An autonomous vehicle has the privilege of abundant data drawn from many sources, but abundance raises a question of provenance: when we care about one specific event in the scene, which source actually carries the evi dence for it? Identifying that source matters be yond attribution, because a system that weighs every channel at once lets the irrelevant ones di lute the decision, and more input is not the same as more information. GoldenViewVQA poses this question in a controlled form, asking a sys tem to name which of six synchronised vehicle cameras carries the evidence for a question, and to answer that question. We introduce a novel two-stage system built on symbolic scene serialisation. We sweep all six views with a de tector fine-tuned on nuScenes, back-project ev ery detection onto the ground plane, associate detections across cameras into single objects that carry an explicit view-set, and render the scene as text. A language model then names the supporting view and the answer, reading either the serialisation alone (System 1) or the serialisation together with the six raw images (System 2). The pixels help the system locate evidence, not answer questions: System 2 lifts view macro-accuracy to 0.68, against 0.38 for System 1 and 0.14 for an always-CAM_FRONT baseline. Our best run reaches 0.78 joint accu racy, 0.83 view accuracy and 0.65 view macro accuracy on the official test split. Answer accu racy already reaches 0.95 with no image at all: option phrasing alone largely solves the answer head, leaving nearly all the measurable signal in the view head.
Anthology ID:
2026.groundlm-1.90
Volume:
Proceedings of the 1st Workshop on Grounding Language Models: Learning Faithfully and Efficiently (GroundLM 2026)
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Yimu Wang, Yee Man Choi, Di Wu, Siqi Ouyang, Mozhgan Nasr Azadani, Yi R. (May) Fung
Venues:
GroundLM | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
1214–1220
Language:
URL:
https://aclanthology.org/2026.groundlm-1.90/
DOI:
Bibkey:
Cite (ACL):
Mostafa Gaafar and Omar Mokhtar Gaber Saqr. 2026. Ensar at GroundLM 2026 Shared Tasks: Symbolic Scene Serialisation for View-Level Evidence Identification. In Proceedings of the 1st Workshop on Grounding Language Models: Learning Faithfully and Efficiently (GroundLM 2026), pages 1214–1220, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Ensar at GroundLM 2026 Shared Tasks: Symbolic Scene Serialisation for View-Level Evidence Identification (Gaafar & Saqr, GroundLM 2026)
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PDF:
https://aclanthology.org/2026.groundlm-1.90.pdf