I used the train tracks too, I was just giving the location of a specific set of cables people can use if they wanted.
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About finding all the shards. If you do download a map with the loctions of all the shards, it'd be a good idea to print it out and take a pen and mark each location off as you go. It can be quite boring to go building to building and constantly checking the map, but I highly doubt I would have found all the shards without it. Be careful though as you could easily find yourself accidently making a mistake on the map. While I was really lucky that the last shard I needed was in an area that I was already suspicious of the markings I had made on the map, it turned out that I had marked the location of the missing shard as found and it was by chance that I happened to see it as I was triple checking the area.
Also, some shards can be hard to see on the map you print out (depending on your source, blue shard dots on top of the dark colors of the map) as well as on your mini-map in-game especially shards over water. Lastly, I believe that there is a limit on the distance the shard is away from you and being able to detect it. For example, you can't sense the shard on the highest building in the historic district (near ground zero) from street level. Also, there's one shard that wont appear on your map at all because it's on top of a broken pier that you have to hop from post to post to get (neon district I believe).
