Read the strike-by-expiration Heat Map

Read the two-dimensional selection

Heat Map places strike and expiration on separate axes and colors each returned cell by the chosen metric. It can show modeled exposure, OI, flow or available contract fields, so the same layout can answer very different questions. Open Gamma → Heat map or add the tool to Map. First identify the metric and legend; a similar color in another metric does not mean a comparable economic amount.

Choose a usable grid

A small focused grid is easier to validate than a full screen of compressed cells.

1. Set the symbol, session, date and eligible historical minute.
2. Choose the metric and call/put/net side.
3. Set expiration bounds with the expiry control.
4. Choose a strike neighborhood or explicit strike range.
5. Hover a cell and read its exact strike, expiration, value and provenance.
6. Adjust the scale only after confirming the measurement and sign convention.

Cell meaning changes with the metric

Gamma dollars, premium dollars, contract counts and IV percentages are not interchangeable. A gamma cell is a strike-expiration aggregate, not a particular trade. A flow cell depends on the selected admitted prints; OI depends on its dated snapshot. A listed zero, no listed contract and unavailable input can have different meanings. Tooltips and quality notices carry that distinction more reliably than a blank or muted color.

Worked interpretation: one bright cell

Suppose one near-expiry strike is brightest on net GEX. Hover it, record the value and date, then switch to OI for the same selection. A large OI count may help explain the modeled concentration, but the GEX scale also depends on Greek valuation and model signs. Switch to premium and the cell can become ordinary because executed activity is a separate dataset. The exercise compares related evidence without treating the three values as substitutes.

Troubleshoot missing rows and misleading color comparisons

Widen strike and expiration bounds to check whether the desired contract is outside the request. Inspect pending-history or access states for a historical minute. Recheck automatic color scaling after changing metric or side; the same shade can represent a different range. If reporting a suspect cell, include its hovered strike/expiry identity and the legend rather than a screenshot containing only the brightest patch.

Model, perspective and units

Exposure is a sensitivity calculation, not an execution total. GEX means gamma exposure, DEX means delta exposure, VEX means vanna exposure, and CEX means charm exposure; charm can also be called CHEX. VEX does not mean vega in these tools. Select the metric before comparing colors or magnitudes. Per 1% move, per $1 move and per unit are distinct choices. Read the returned unit rather than assuming that every displayed dollar amount means money paid for contracts.

Classic OI applies a positioning proxy to dated open interest. Flow-adjusted modeling incorporates eligible classified intraday volume into that proxy. Neither reveals actual dealer inventory or every hedge. Dealer and customer perspectives can reverse signs while retaining the underlying sensitivity calculation. A positive bar is therefore meaningful only with its metric, model, perspective, expiration selection and valuation time. Record those settings together when sharing a view, and match them before expecting two tools to return comparable values.

Use a cell as an audit point

Choose one strike-expiration coordinate and record the metric, side and hovered value before changing views. With exposure, compare the same selected expiry in Exposure by Strike. With OI, compare the dated OI tool. With premium or volume, compare the filtered flow context. The cell is a useful join point only when its scope matches; selecting all expirations in another tool changes the population. Do not infer a single exact call or put from a net cell until its contributing side/root context is clear.

Color scale deserves the same attention as the number. An automatically scaled heat map can make a modest value look saturated after a larger concentration is filtered out. Conversely, a large outlier can make meaningful smaller cells appear faint. This is a presentation effect, not missing data. Hover values and units remain the audit evidence. Preserve the legend and selected bounds in screenshots, and distinguish no-listed-contract, valid zero and unavailable input in any written interpretation rather than describing all three as an empty square.