C# code to download & stitch together the Submarine Cable Map 2019 from Telegeography

main.cs

using System;
using System.Drawing;
using System.Net;

namespace ImageBuilder
{
    class Program
    {
        static Image[,] m_Images;

        static void Main(string[] args)
        {
            // High resolution: 6
            // Rows: 64
            // Columns: 64
            m_Images = new Image[64, 64];

            for (int i = 0; i < m_Images.GetLength(0); i++)
            {
                for (int j = 0; j < m_Images.GetLength(1); j++)
                {
                    //DownloadImage(6, i, j);
                    m_Images[i, j] = LoadImage(6, i, j);
                }
            }

            //
            // Calculate the maximum size
            //
            int totalWidth  = 0;
            int totalHeight = 0;

            for (int i = 0; i < m_Images.GetLength(0); i++)
                totalHeight += m_Images[i, 0].Height;

            for (int i = 0; i < m_Images.GetLength(1); i++)
                totalWidth += m_Images[0, i].Width;

            //
            // Now create the final bitmap
            //
            Bitmap finalImg = new Bitmap(totalWidth, totalHeight);
            finalImg.SetResolution(m_Images[0, 0].HorizontalResolution, m_Images[0, 0].VerticalResolution);

            Graphics draw = Graphics.FromImage(finalImg);
            draw.Clear(Color.Black);

            int h = 0;
            int w = 0;
            for (int i = 0; i < m_Images.GetLength(0); i++)
            {
                w = 0;

                for (int j = 0; j < m_Images.GetLength(1); j++)
                {
                    draw.DrawImage(m_Images[i, j], w, h);

                    w += m_Images[i, j].Width;
                }

                h += m_Images[i, 0].Height;
            }

            finalImg.Save("out.png", System.Drawing.Imaging.ImageFormat.Png);
        }

        static bool DownloadImage(int Resoltion, int Row, int Col)
        {
            string localFilename = String.Format("{0}_{1}_{2}.png", Resoltion, Col, Row);
            string remoteFilename = String.Format("https://tiles.telegeography.com/maps/submarine-cable-map-2019/{0}/{1}/{2}.png8", Resoltion, Col, Row);

            try
            {
                using (WebClient client = new WebClient())
                {
                    client.DownloadFile(remoteFilename, localFilename);
                }
            }
            catch (Exception)
            {
                return false;
            }

            return true;
        }

        static Image LoadImage(int Resoltion, int Row, int Col)
        {
            string localFilename = String.Format(Environment.CurrentDirectory + @"\{0}_{1}_{2}.png", Resoltion, Col, Row);

            return Image.FromFile(localFilename);
        }
    }
}