public static class MySettings
{
    // ...
    public static string ChartFolder = "..\\";                      //海圖文件夾
}

//窗體級變量，存儲海圖文件
private S57File[] readers;

    //遍歷海圖總文件夾，將子文件夾里的海圖文件夾挑選出來
    var chartFolders = new List<string>();
    foreach (var folder in Directory.GetDirectories(MySettings.ChartFolder).OrderBy(x => x))
    {
        var fileName = Path.GetFileNameWithoutExtension(folder);
        //包含000文件，是海圖文件夾
        if(File.Exists($"{folder}\\{fileName}.000"))
        {
            chartFolders.Add(folder);
        }
    }

    //加載海圖，完成坐標轉(zhuǎn)換
    var len = chartFolders.Count;
    readers = new S57File[len];
    for (int i = 0; i < len; i++)
    {
        readers[i] = new S57File(chartFolders[i]);
        var comf = (double)readers[i].COMF;
        var somf = (double)readers[i].SOMF;
        foreach (var s in readers[i].Spatials.Values)
        {
            if(s.YCOOs != null)
            {
                s.Latitudes = new double[s.YCOOs.Length];
                s.Longitude = new double[s.XCOOs.Length];
                for (int j = 0; j < len; j++)
                {
                    s.Latitudes[j] = s.YCOOs[j] / comf;
                    s.Longitude[j] = s.XCOOs[j] / comf;
                }
            }
            if (s.VE3Ds != null)
            {
                s.Depths = new double[s.VE3Ds.Length];
                for (int j = 0; j < len; j++)
                {
                    s.Depths[j] = s.VE3Ds[j] / somf;
                }
            }
        }

        if(readers[i].SLAT == 100d) //不存在海圖邊界信息，則重新計算下
        {
            readers[i].WLON = readers[i].Spatials.Values.Where(x => x.Longitude != null).Min(x => x.Longitude.Min());
            readers[i].ELON = readers[i].Spatials.Values.Where(x => x.Longitude != null).Max(x => x.Longitude.Max());
            readers[i].SLAT = readers[i].Spatials.Values.Where(x => x.Latitudes != null).Min(x => x.Latitudes.Min());
            readers[i].NLAT = readers[i].Spatials.Values.Where(x => x.Latitudes != null).Max(x => x.Latitudes.Max());
        }

        //通過查詢表匹配符號化指令
        foreach (var f in readers[i].Features.Values)
        {
            f.LookUp = S52Tools.FindLookUpEntry(f);
        }

        //通過符號化指令排序
        //第一排序字段為：顯示優(yōu)先級 
        //第二排序字段為：面 > 線 > 點
        //第三排序字段為：分組
        readers[i].Features = readers[i].Features.OrderBy(x => x.Value.LookUp.Priority)
            .ThenByDescending(x => x.Value.PRIM)
            .ThenBy(x => x.Value.GRUP)
            .ToDictionary(k => k.Key, v => v.Value);
    }

     //確定顯示區(qū)域中心及顯示比例尺
     double slat = 100, nlat = -100, elon = -200, wlon = 200;
     uint cscl = 0;
     for (int i = 0; i < len; i++)
     {
         if (slat > readers[i].SLAT) slat = readers[i].SLAT;
         if (nlat < readers[i].NLAT) nlat = readers[i].NLAT;
         if (wlon > readers[i].WLON) wlon = readers[i].WLON;
         if (elon < readers[i].ELON) elon = readers[i].ELON;
         if (readers[i].CSCL > cscl) cscl = readers[i].CSCL;
     }

     //視窗中心位置
     initCenterPos.Latitude = (slat + nlat) / 2;
     initCenterPos.Longitude = (elon + wlon) / 2;

    //顯示比例尺
    if (cscl == 0) //沒有指定編譯比例尺，則將所有海圖都顯示在視窗中
    {
        var deltaY = (nlat - slat) * 0.1;

        var pix_X = (elon - wlon) * 60 * 1.2;
        var pix_Y = (GeoTools.MP(nlat + deltaY) - GeoTools.MP(slat - deltaY));
        if (pix_X / pix_Y < (double)current_Width / current_Height)
        {
            current_Scale = (uint)(pix_X * GeoTools.MinPP / current_Width);
        }
        else
        {
            current_Scale = (uint)(pix_Y * GeoTools.MinPP / current_Height);
        }
    }
    else
    {
        current_Scale = cscl;
    }

    private void DrawEnc(SKCanvas ca)
    {
        //右上角位置
        var trPos = GeoTools.ScreenPointToGeoPosition(current_Width, 0, current_Scale, current_Dx, current_Dy);
        //左下角位置
        var blPos = GeoTools.ScreenPointToGeoPosition(0, current_Height, current_Scale, current_Dx, current_Dy);
        //區(qū)域矩形
        var zoneRec = new SKRect(0, 0, current_Width, current_Height);

        for (int i = 0; i < readers.Length; i++)
        {
            var reader = readers[i];
            //粗略判斷海圖范圍是否在視窗內(nèi)
            if (GeoTools.ShouldNotDisplay(trPos, blPos, reader.NLAT, reader.SLAT, reader.ELON, reader.WLON)) continue;

            //下一步操作
        }
    }

            //下一步操作
            foreach (var f in reader.Features.Values)
            {
                if (f.PRIM == 255) continue;
                //超出比例尺
                if (current_Scale > f.ScaleMinium || current_Scale < f.ScaleMaximum) continue;
                //沒有繪制指令
                if (f.LookUp.Instructions == null) continue;

                #region 繪制
            }