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The navigation icon which was a part of Google Maps was recently removed due to an upgrade to Google Maps. When your Maps app updated it removed the Navigation icon. To navigate with the new version of Maps you have to do it from within the Maps app.
If you want to regain the Navigation app you can remove the update to Google Maps and revert back to the old version and you'll have to avoid updating again. To remove the update you need to go to settings > Apps or Application Manager, scroll down the list of downloaded apps until you find maps. Click on maps and then click uninstall updates. It will ask if you want to remove, Select yes and it will take you back to old version of maps
I hope this info helps but if you need further info please submit another question using the Guest Questions form or consider registering for a more interactive response.
Thanks
