--- title: "Chin Position Relative to the Frankfort Plane: What FaceIQ Labs Measures and How to Read It" description: "FaceIQ Labs' Chin Position Relative to the Frankfort Plane compares the chin's most forward point with the nasal root in a side photo. See the formula, sign convention and why millimeters are estimates." canonical: "https://appear.faceiqlabs.com/support/harmony/recession-relative-to-frankfort-plane" --- # Chin Position Relative to the Frankfort Plane: What FaceIQ Labs Measures and How to Read It In FaceIQ Labs' Harmony analysis, Chin Position Relative to the Frankfort Plane is a side-view jaw measurement of the horizontal position of the chin's most forward point (pogonion) relative to the nasal root (nasion), calculated as (Pogonion x − nasion x) × photo scale. Negative means the chin is behind the nasal root; positive means in front. Millimeter values are estimates. ## Key facts - Formula: (Pogonion x − nasion x) × photo scale - Nasion is the nasal root, subnasale is the nose base, and pogonion is the most forward chin point - Frankfort refers to the direction from the ear-opening landmark to the lower orbital landmark - Negative result: the chin point lies behind the nasal root in the oriented profile - Positive result: the chin point lies in front of the nasal root in the oriented profile - The formula uses horizontal coordinates in the oriented image and does not independently rotate points into a Frankfort coordinate system - Millimeter values assume a 190 mm hairline-to-chin height and are estimates, not calibrated physical measurements - The report name does not make this a clinical diagnosis of mandibular recession - FaceIQ Labs categorizes it under Harmony, side view, jaw - FaceIQ Labs standardizes side photos to the Frankfort horizontal plane during landmarking, and Harmony is weighted roughly 60% from the front photo and 40% from the side photo ## What does Chin Position Relative to the Frankfort Plane measure? FaceIQ Labs' Chin Position Relative to the Frankfort Plane measures the horizontal position of the chin's most forward point (pogonion) relative to the nasal root (nasion) in the oriented side photo. The formula is (Pogonion x − nasion x) × photo scale. It compares the chin with an upper-face reference rather than judging the chin alone. In FaceIQ Labs' guides, subnasale means the nose base, and Frankfort refers to the direction from the ear-opening landmark to the lower orbital landmark. ## What do positive and negative values mean? - Negative: in FaceIQ Labs' oriented profile, the chin point lies behind the nasal root. - Positive: the chin point lies in front of the nasal root in the oriented profile. - The result depends on where the nasal root sits as well as on the chin, so it is a relative comparison. - FaceIQ Labs says the measurement adds directional information to profile angles. ## Is the measurement truly calculated in a Frankfort coordinate system? Not fully. FaceIQ Labs states that clinical profile analysis uses head references to compare projection, whereas its own Chin Position Relative to the Frankfort Plane measurement uses horizontal coordinates in the already-oriented image. The formula does not independently rotate the points into a Frankfort coordinate system, so checking head orientation in the photo matters when reading the result. ## How accurate are the millimeter values? The millimeter values in FaceIQ Labs' Chin Position Relative to the Frankfort Plane result are approximate. FaceIQ Labs scales the photo using an assumed 190 mm hairline-to-chin height, so values are estimates, not calibrated physical measurements. For example, a chin 15 units behind the nasal root at 0.2 estimated mm per unit reads −3 mm. Example values are not a target range. ## Is Chin Position Relative to the Frankfort Plane a diagnosis of mandibular recession? No. FaceIQ Labs states that the report name does not make its Chin Position Relative to the Frankfort Plane measurement a clinical diagnosis of mandibular recession. Its guidance is to check head orientation in the photo first. The worked example values explain the calculation; they are not a target range and are not measurements of the schematic. ## Where does the idea behind this measurement come from? FaceIQ Labs describes Chin Position Relative to the Frankfort Plane as a FaceIQ adaptation of clinical profile analysis, which uses head references to compare projection. It cites Holdaway's 1984 paper, "A soft-tissue cephalometric analysis and its use in orthodontic treatment planning. Part II," which explains how lip, chin and skeletal relationships must be considered together. FaceIQ Labs notes its score weights and reference ranges are model settings that the papers do not collectively validate. ## Where does it fit in FaceIQ Labs' Harmony analysis? Chin Position Relative to the Frankfort Plane is one of FaceIQ Labs' Harmony measurements, listed under the side view and jaw region. Related guides cover Gonial Angle, Mandibular Plane Angle, Ramus to Mandible Ratio and Gonion-to-Mouth Line. Harmony is weighted roughly 60% from the front photo and 40% from the side photo, and side photos are standardized to the Frankfort horizontal plane during landmarking. ## Frequently asked questions ### How does FaceIQ Labs calculate Chin Position Relative to the Frankfort Plane? It uses (Pogonion x − nasion x) × photo scale, where pogonion is the most forward chin point and nasion is the nasal root, based on horizontal coordinates in the oriented side photo. ### What does a negative value mean? A negative value means the chin's most forward point lies behind the nasal root in the oriented profile. ### What does a positive value mean? A positive value means the chin's most forward point lies in front of the nasal root in the oriented profile. ### Are the millimeter results exact? No. FaceIQ Labs assumes a 190 mm hairline-to-chin height to scale the photo, so the values are estimates, not calibrated physical measurements. ### Does this measurement diagnose mandibular recession? No. FaceIQ Labs says the report name does not make it a clinical diagnosis, and advises checking head orientation first. ### Does FaceIQ Labs rotate landmarks into a true Frankfort coordinate system for this measurement? No. The formula uses horizontal coordinates in the oriented image and does not independently rotate the points into a Frankfort coordinate system. ## Pages on this host This is one page of several on this host. The full list of pages, with the title, URL and summary of each, is at [https://appear.faceiqlabs.com/.well-known/appear-index.json](https://appear.faceiqlabs.com/.well-known/appear-index.json). 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