page_title: Ground Zero Indicator
hierarchical_section_title: Ground Zero Indicator
caption_attribution_description: Ground Zero Indicator
context_page_description: The Ground Zero Indicator, known by the acronym GZI was a specially designed shadowgraph instrument used by the British Royal Observer Corps during the Cold War to locate the Ground Zero of any nuclear explosion.
context_section_description: The Ground Zero Indicator, known by the acronym GZI was a specially designed shadowgraph instrument used by the British Royal Observer Corps during the Cold War to locate the Ground Zero of any nuclear explosion.
caption: Ground Zero Indicator, showing the interior graticules (and the insert at bottom left shows the instrument mounted with its cover in place)
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