Clearance

Current Effective Date: 0901Z 14 May 2026 to 0901Z 09 Jul 2026 Clearance The Clearance dataset provides information about the highest terrain or obstacle elevation within a quadrant or bin on a chart. Clearance values can be used to determine the lowest recommended altitudes that can be flown within a bin or quadrant when taking terrain and obstacle data into account. Depending on the type of clearance and location of the bin, additional buffers may be used in the calculation. The quadrant or bin sizes vary from product to product. Clearance information is published every 56 days by the U.S. Department of Transportation, Federal Aviation Administration – Aeronautical Information Services. Types of clearance data include: Off Route Obstruction Clearance Altitude (OROCA) OROCAs are depicted on the Enroute (IFR) chart series. They include a 1000 foot vertical buffer over the highest terrain or obstacle feature in non-mountainous areas and a 2000 foot vertical buffer in designated mountainous area within the United States. These values include a horizontal buffer of 4 NM in all directions outside of the bin. Off Route Terrain Clearance Altitude (ORTCA) ORTCAs are shown on the Enroute (IFR) chart series. ORTCAs are depicted for charted areas in Mexico and the Caribbean that are located outside the U.S. Air Defense Identification Zone (ADIZ). ORTCAs include a 3000 foot vertical buffer over the highest terrain or obstacle feature. These values include a horizontal buffer of 4 NM in all directions outside of the bin. Maximum Elevation Figure (MEF) – Future Enhancement MEFs are depicted on the Visual (VFR) chart series. MEF values include a 100 foot buffer over the highest obstacle feature and a 300 foot buffer over the highest terrain feature in each bin, and are then rounded up to the next 100 foot value. There is no horizontal buffer included in the MEF calculation.现行有效时段：2026年5月14日0901Z 至 2026年7月9日0901Z 【数据说明】本净空（Clearance）数据集提供航图象限或网格单元内最高地形与障碍物高程信息。净空值可用于结合地形与障碍物数据，确定网格单元或象限内的最低推荐飞行高度。根据净空类型与网格单元位置的差异，计算过程中可能需加入额外缓冲余量。不同航图产品的象限或网格单元尺寸各不相同。 本数据集由美国运输部联邦航空管理局航空信息服务部门每56天发布一次。 净空数据类型包括： 1. 航线外障碍物净空高度（Off Route Obstruction Clearance Altitude, OROCA） 该高度标注于航路仪表飞行规则（Instrument Flight Rules, IFR）航图系列中。在美国境内非山区，其针对最高地形或障碍物特征设置1000英尺垂直缓冲余量；在指定山区则设置2000英尺垂直缓冲余量。该类高度值在网格单元外所有方向均包含4海里的水平缓冲余量。 2. 航线外地形净空高度（Off Route Terrain Clearance Altitude, ORTCA） 该高度标注于航路IFR航图系列中，用于美国防空识别区（Air Defense Identification Zone, ADIZ）以外的墨西哥及加勒比海制图区域。其针对最高地形或障碍物特征设置3000英尺垂直缓冲余量，且在网格单元外所有方向包含4海里的水平缓冲余量。 3. 最大高程数值（Maximum Elevation Figure, MEF）—— 未来增强功能 该数值标注于目视飞行规则（Visual Flight Rules, VFR）航图系列中。MEF计算方式为：对每个网格单元内的最高障碍物特征加入100英尺缓冲、最高地形特征加入300英尺缓冲，随后向上取整至最近的100英尺整数。MEF计算过程不包含水平缓冲余量。