# Speeds The difference between Equivalent Airspeed (EAS) and Ground Speed (GS) lies in what they measure and the factors they account for: **Equivalent Airspeed (EAS):** **Definition**: EAS is the airspeed corrected for changes in air density due to altitude and atmospheric conditions. It represents the dynamic pressure acting on the aircraft. What it measures: It shows the aerodynamic performance of the aircraft and is primarily used for understanding flight dynamics, such as stall speed, maneuvering limits, and structural loads. Key Factors: EAS is influenced by air density (altitude and temperature) but does not account for wind. **Ground Speed (GS):** **Definition:** GS is the actual speed of the aircraft relative to the ground. It's the speed at which the aircraft is moving over the Earth's surface. What it measures: It shows how quickly the aircraft is traveling from point A to point B on the ground. Key Factors: GS is influenced by true airspeed (TAS) and wind. A tailwind increases GS, while a headwind decreases it. **Key Differences:** Purpose: EAS is related to aerodynamic performance; GS is related to navigation and how fast you reach your destination. Altitude & Wind: EAS accounts for air density but doesn't include wind effects. GS includes wind (headwind/tailwind) but doesn't consider air density. For example, an aircraft can have a high EAS but a low GS if flying into a strong headwind. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.unisphere.io/unisphere-apis/explanatory-notes/speeds.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.