The SpotGamma HIRO Indicator is an options based indicator by SpotGamma running atop of Bookmap charts.

HIRO stands for “Hedging Impact Real-Time Options”. One of the strongest forces in futures markets is that of options hedging. Large options transactions can often require large hedges which can lead to rapid fluctuations in markets.

Now, in real time, SpotGamma decodes these large options trades on Bookmap. Each time an option trade takes place, SpotGamma’s proprietary algorithm determines the estimated hedging impact which is then displayed as a customizable indicator on the relevant underlying symbol chart in Bookmap.

From: https://support.spotgamma.com/hc/en-us/articles/1500010723641-What-is-the-SpotGamma-HIRO-Indicator-