With the development of cartography, the history of landscapes has taken more and more importance to delineate the development of social settlements. As cited from [1] the illustration, let us take the famous depiction of Napoleon’s march on Moscow published by Charles Joseph Minard in 1861 ( a detailed description can be found in Tufte ). The author engages the readers in the exploration of the fate of Napoleon’s army in the Russian campaign of 1812-1813. Beginning at the Polish-Russian border, the thick band shows the size of the army at each position. The path of Napoleon’s retreat from Moscow in the cold winter is depicted by the dark lower band, which is tied to temperature and time scales. Tufte identified six separate variables that were shown within Minard’s drawing. First, the line width continuously marked the size of the army. Second and third, the line itself showed the latitude and longitude of the army as it moved. Fourth, the lines themselves showed the direction that the army was travelling, both in advance and retreat. Fifth, the location of the army with respect to certain dates was marked. Finally, the temperature along the path of retreat was displayed. It can also be noted that, despite of the schematic character of the drawing with its rudimentary cartography, Minard depicted some features of the underlying territory (specifically, rivers and towns) he deemed essential for the understanding of the story.

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I’m posting today some source code about the famous TomTom One .OV2 file formats. These files are the one used by TomTom to store Point of Interest information within their navigation systems. However such format is proprietary, the data specs can be found in the TomTom website (see this PDF at section 2.4). I wrote down a simple procedure that gathers record by record only the simple POI records. Actually the OV2 format is a little bit more complicated than a simple list of POIs and it can be subjected to changes and version incompatibilities. I tested it with POIs taken from my TomTom ONE XL and ti worked great, however if the OV2 files contains proprietary or special record types (not specified in TomTom data sheets) these procedures will simply stop since it is not possible for this format to distinguish between a corrupted file or non standard encoding.

I hope you’ll find it interesting.

Java version:

package readers;

import java.io.FileInputStream;
import java.io.IOException;

public class OV2RecordReader {

	public static String[] readOV2Record(FileInputStream inputStream){
		String[] record = null;
		int b = -1;
		try{
			if ((b = inputStream.read())> -1) {
				// if it is a simple POI record
				if (b == 2) {
					record = new String[3];
		    	    long total = readLong(inputStream);

		    	    double longitude = (double) readLong(inputStream) / 100000.0;
		    	    double latitude = (double) readLong(inputStream) / 100000.0;

		    	    byte[] r = new byte[(int) total - 13];
		    	    inputStream.read(r);

		    	    record[0] = new String(r);
		    	    record[0] = record[0].substring(0,record[0].length()-1);
		    	    record[1] = Double.toString(latitude);
		    	    record[2] = Double.toString(longitude);
		    	}
				//if it is a deleted record
				else if(b == 0){
					byte[] r = new byte[9];
		    	    inputStream.read(r);
				}
				//if it is a skipper record
				else if(b == 1){
					byte[] r = new byte[20];
		    	    inputStream.read(r);
				}
				else{
					throw new IOException("wrong record type");
				}
			}
			else{
				return null;
			}
		}
		catch(IOException e){
			e.printStackTrace();
		}
		return record;
	}

	private static long readLong(FileInputStream is){
		long res = 0;
		try{
			res = is.read();
			res += is.read() <<8;
			res += is.read() <<16;
			res += is.read() <<24;
		}
		catch(IOException e){
			e.printStackTrace();
		}
		return res;
	}
}

C# Version

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;

namespace OV2Reader
{
 class Program
 {
 static void Main(string[] args)
 {
 string filename = @"C:\test.ov2";
 FileStream infile = new FileStream(filename, FileMode.Open, FileAccess.Read);

 while (infile.Length != infile.Position)
 {
 string[] data = readOV2Record(infile);
 if (data != null)
 {
 for (int i = 0; i < data.Length; i++)
 {
 Console.WriteLine(data[i]);
 }
 }
 }

 Console.WriteLine("exiting....");
 Console.ReadKey();
 }

 static string[] readOV2Record(FileStream inputStream)
 {
 String[] record = null;
 int b = -1;

 if ((b = inputStream.ReadByte()) > -1)
 {
 // if it is a simple POI record
 if (b == 2)
 {

 long total = readLong(inputStream);

 double longitude = (double)readLong(inputStream) / 100000.0;
 double latitude = (double)readLong(inputStream) / 100000.0;

 byte[] r = new byte[(int)total - 13];
 inputStream.Read(r, 0, (int)total - 13);

 record = new String[3];
 string s = System.Text.ASCIIEncoding.ASCII.GetString(r);
 record[0] = s;
 record[0] = record[0].Substring(0, record[0].Length - 1);
 record[1] = latitude.ToString();
 record[2] = longitude.ToString();
 }
 //if it is a deleted record
 else if (b == 0)
 {
 byte[] r = new byte[9];
 inputStream.Read(r, 0, 9);
 }
 //if it is a skipper record
 else if (b == 1)
 {
 byte[] r = new byte[20];
 inputStream.Read(r, 0, 20);
 }
 else
 {
 //
 return null;
 }
 }
 else
 {
 return null;
 }

 return record;
 }

 private static long readLong(FileStream fis)
 {
 long res = 0;

 res = fis.ReadByte();
 res += fis.ReadByte() << 8;
 res += fis.ReadByte() << 16;
 res += fis.ReadByte() << 24;
 return res;
 }
 }
}

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