Chart Speed

Category: Electronics

Chart speed (also called scroll speed) is the rate at which sonar information moves across the fish finder screen from right to left. Higher chart speeds show more detail and separate targets more clearly but may stretch the image horizontally. Lower chart speeds compress the display and can cause fish arches and structure to appear blurred or merged together. The optimal chart speed depends on boat speed and the type of fishing: when the boat is stationary or moving slowly (as during vertical jigging or drop shotting), chart speed should be reduced to prevent stretching the sonar image. When the boat is moving at moderate speed (as during trolling or searching), chart speed should be increased to maintain accurate target proportions. Most experienced anglers set chart speed to its highest setting and adjust downward as needed based on boat speed. On units that allow it, setting chart speed to 'Auto' ties the scroll rate to GPS speed, maintaining consistent image quality regardless of how fast the boat is moving. Understanding chart speed is essential for accurately interpreting sonar returns — an arch that appears to be a 5-pound bass at high chart speed may be a 1-pound fish at a more appropriate setting.