Numerous researchers have tried to trace his route across the Southwest. As he did not begin writing his chronicle until he was back in Spain, he had to rely on memory. He did not have the instruments (clock and astrolabe) to determine his location; he had to rely on dead reckoning, and was uncertain of his route. Aware that his recollection has numerous errors in chronology and geography, historians have worked to put together pieces of the puzzle to discern his paths.