An apparatus to track a mobile subject based on Global Navigation Satellite Systems, GNSS, data, comprising: an actionable position and speed determination unit configured to receive GNSS data and determine an actionable position and an actionable speed of the mobile subject; a boundary test unit configred to evaluate: a boundary violation according to a current actionable position and a current actionable speed of the mobile subject relative to a predetermined boundary; and a motion detector to detect motion of the mobile subject independently of the GNSS data, wherein the position and speed determination unit is configured to determine the current actionable position as a sum of a prior actionable position and a product of a degraded position difference and a position tracking coefficient, the degraded position difference being a product of a position degrade coefficient and a difference between a current GNSS position and the prior actionable position, the position degrade coefficient being a function of most recent and prior GNSS position solution metrics and GNSS signal metrics, and the position tracking coefficient being a function of the actionable speed and a detected motion from the motion detector, wherein the position and speed determination unit is configured to determine the current actionable speed as a function of a prior actionable speed and a degraded speed estimate, the degraded speed estimate being a product of a speed estimate and a speed degrade coefficient, the speed estimate being a function of the prior speed estimate and a GNSS speed estimate, the speed degrade coefficient being a function of most recent and prior GNSS speed solution metrics, and the speed degrade coefficient being a function of the GNSS signal metrics, and wherein the apparatus is configured to determine the GNSS signal metrics which include a quantity representative of the aggregate observable GNSS signal to noise ratio, observable indicating all GNSS signals used to determine the GNSS position and speed. an actionable position and speed determination unit configured to receive GNSS data and determine an actionable position and an actionable speed of the mobile subject; a boundary test unit configred to evaluate: a boundary violation according to a current actionable position and a current actionable speed of the mobile subject relative to a predetermined boundary; and a motion detector to detect motion of the mobile subject independently of the GNSS data, wherein the position and speed determination unit is configured to determine the current actionable position as a sum of a prior actionable position and a product of a degraded position difference and a position tracking coefficient, the degraded position difference being a product of a position degrade coefficient and a difference between a current GNSS position and the prior actionable position, the position degrade coefficient being a function of most recent and prior GNSS position solution metrics and GNSS signal metrics, and the position tracking coefficient being a function of the actionable speed and a detected motion from the motion detector, wherein the position and speed determination unit is configured to determine the current actionable speed as a function of a prior actionable speed and a degraded speed estimate, the degraded speed estimate being a product of a speed estimate and a speed degrade coefficient, the speed estimate being a function of the prior speed estimate and a GNSS speed estimate, the speed degrade coefficient being a function of most recent and prior GNSS speed solution metrics, and the speed degrade coefficient being a function of the GNSS signal metrics, and wherein the apparatus is configured to determine the GNSS signal metrics which include a quantity representative of the aggregate observable GNSS signal to noise ratio, observable indicating all GNSS signals used to determine the GNSS position and speed.