A work vehicle, comprising: a vehicle; a first antenna and a second antenna, which are both mounted to the vehicle to receive a radio wave of a satellite positioning system; a receiver configured to output position information of the first antenna based on the radio wave and a baseline direction between the first antenna and the second antenna; a sensor configured to measure a velocity, an acceleration, and an angular velocity of the vehicle; and a control device configured to estimate a location and a posture of the vehicle, wherein the control device has a function of calculating a first vehicle direction based on installation information of the first antenna and the second antenna with respect to the vehicle; wherein the control device is characterized by: a detection function of detecting a steady traveling based on the velocity, the acceleration, and the angular velocity, the steady traveling including a turning traveling to travel along a circumference having a same center and a same radius and a straight advancing traveling to travel in a straight line, the steady traveling having an average value of the velocity higher than a predetermined velocity threshold; a function of setting a moving vector calculated based on a difference between the current position information of the first antenna and the position information of the first antenna one cycle before as a second vehicle direction when the straight advancing traveling is detected as the steady traveling, and calculating a second vehicle direction based on a turning center and a rotational center of the vehicle when the turning traveling is detected as the steady traveling; a function of calculating a direction correction parameter for correcting the first vehicle direction based on the second vehicle direction; and an estimation function of estimating the location and the posture of the vehicle based on the direction correction parameter and the first vehicle direction. a vehicle; a first antenna and a second antenna, which are both mounted to the vehicle to receive a radio wave of a satellite positioning system; a receiver configured to output position information of the first antenna based on the radio wave and a baseline direction between the first antenna and the second antenna; a sensor configured to measure a velocity, an acceleration, and an angular velocity of the vehicle; and a control device configured to estimate a location and a posture of the vehicle, wherein the control device has a function of calculating a first vehicle direction based on installation information of the first antenna and the second antenna with respect to the vehicle; wherein the control device is characterized by: a detection function of detecting a steady traveling based on the velocity, the acceleration, and the angular velocity, the steady traveling including a turning traveling to travel along a circumference having a same center and a same radius and a straight advancing traveling to travel in a straight line, the steady traveling having an average value of the velocity higher than a predetermined velocity threshold; a function of setting a moving vector calculated based on a difference between the current position information of the first antenna and the position information of the first antenna one cycle before as a second vehicle direction when the straight advancing traveling is detected as the steady traveling, and calculating a second vehicle direction based on a turning center and a rotational center of the vehicle when the turning traveling is detected as the steady traveling; a function of calculating a direction correction parameter for correcting the first vehicle direction based on the second vehicle direction; and an estimation function of estimating the location and the posture of the vehicle based on the direction correction parameter and the first vehicle direction. a detection function of detecting a steady traveling based on the velocity, the acceleration, and the angular velocity, the steady traveling including a turning traveling to travel along a circumference having a same center and a same radius and a straight advancing traveling to travel in a straight line, the steady traveling having an average value of the velocity higher than a predetermined velocity threshold; a function of setting a moving vector calculated based on a difference between the current position information of the first antenna and the position information of the first antenna one cycle before as a second vehicle direction when the straight advancing traveling is detected as the steady traveling, and calculating a second vehicle direction based on a turning center and a rotational center of the vehicle when the turning traveling is detected as the steady traveling; a function of calculating a direction correction parameter for correcting the first vehicle direction based on the second vehicle direction; and an estimation function of estimating the location and the posture of the vehicle based on the direction correction parameter and the first vehicle direction.