Start at Tal’Deic Grounds Wayshrine and go west. As you travel you will notice two towers standing left (south) and right (west) of the entrance into Tal’Deic Fortress. The skyshard is located near the base of the southern tower. Enter the city, circle around the tower and you will see it between a wooden barrel and wooden crates.
Go around the towers standing south of Tal’Deic Fortress entrance and you’ll come across the shard.
The location on the world map. The southern tower is that brownish circle directly under the blue character arrow.
Sand Kingdom Moons - Super Mario Odyssey Power Moons