Swift中高效查询大型GeoJSON文件获取点所属限速区域

问题背景 #

我有一个200MB的包含某国限速信息的GeoJSON文件，文件中用多边形划分不同区域，每个多边形对应一个限速值。目前正在开发一款iOS Swift导航应用，需要查询该GeoJSON文件以获取用户当前所在位置的限速。当前采用线性搜索方案，虽可运行但会导致应用卡顿，性能严重下降。

当前线性搜索实现代码 #

func findSpeedLimit(location: CLLocationCoordinate2D, geoJSON: GeoJSON) -> Int? {
    // Decode the GeoJSON data into a FeatureCollection object
    guard case let .featureCollection(featureCollection) = geoJSON else {
        print("Error: GeoJSON data is not a FeatureCollection")
        return nil
    }
    
    // Create a Point object from the location coordinates
    let point = Point(x: location.longitude, y: location.latitude)
    //print("Looking for speed limit at location: \(location.latitude), \(location.longitude)")
    
    // Loop through the features in the feature collection
    for (index, feature) in featureCollection.features.enumerated() {
        // Check if the feature has a geometry and properties
        guard let geometry = feature.geometry,
              let properties = feature.properties else {
            print("Feature \(index) has no geometry or properties")
            continue
        }
        
        do {
            // Check if the geometry contains the point
            if try geometry.contains(point) {
                // Check if the properties have a speedLimitZoneValue key
                if let speedLimit = properties["speedLimitZoneValue"] {
                    let speedLimitString = String(describing: speedLimit)
                    if let number = Int(speedLimitString.components(separatedBy: CharacterSet.decimalDigits.inverted).joined()) {
                        //print (number)
                        //print("Speed limit found for feature \(index): \(number) km/h")
                        return number
                    }
                    
                } else {
                    print("Feature \(index) has no 'speedLimitZoneValue' property")
                }
            } else {
                //print("Feature \(index) does not contain the point")
            }
        } catch {
            print("Error checking if geometry contains point: \(error)")
        }
    }
    
    return nil
}

已完成的优化 #

借助GEOSwift库实现了预准备几何图形（prepared geometries），通过预编译多边形几何数据，大幅减少每次点-in-多边形判断的计算开销，避免线性搜索中重复的几何处理操作，有效提升查询性能。

内容的提问来源于stack exchange，提问作者Jesse_rs