A method for optimizing the accuracy of position determination and / or reducing the integrity risk of a receiver in a global satellite navigation system having a plurality of satellites (RF1, RF2, RF3, RF4), characterized in that - for at least one satellite (RF1, RF2, RF3, RF4) that is visible to the receiver, a deviation error (AF 1, AF 2) is determined as a function of geometric orientation of the satellite (RF1, RF2, RF3, RF4) relative to the receiver and of at least one system parameter, wherein an integrity parameter is considered as system parameter, - the deviation error (AF 1, AF 2) is determined by an error projection on the basis of an additional deviation error (AF'), wherein the additional deviation error (AF') is determined for the geometric deviation of the satellite (RF1,..., RF4) relative to the receiver, on the basis of a context for the at least one system parameter, the context being previously determined and stored in the receiver, and wherein the error projection performs a transformation into a x-y-coordinate system of the receiver, and - a first and second value (AF 1, AF 2) of the error projection is determined, wherein - the first value (AF 1) for the at least one system parameter is determined on the basis of a first parameter value (s 1) of the additional deviation error (AF'), wherein the first parameter value (s 1) is determined depending on the geometric deviation on the basis of the stored context, - the second value (AF 2) for the at least one system parameter is determined using a modified parameter value (ms 1) of the additional deviation error (AF'), which is modified in comparison to the predetermined parameter value such that the second modified parameter value (ms 1) is determined depending on the geometric deviation from a modified context, which results from a linear displacement of the stored context, and the second modified parameter value is assumed more conservative in comparison to the first parameter value, wherein the more conservative assumption corresponds to a greater error of the system parameter, - the smaller of both values is used as deviation error (AF 1, AF 2). - for at least one satellite (RF1, RF2, RF3, RF4) that is visible to the receiver, a deviation error (AF 1, AF 2) is determined as a function of geometric orientation of the satellite (RF1, RF2, RF3, RF4) relative to the receiver and of at least one system parameter, wherein an integrity parameter is considered as system parameter, - the deviation error (AF 1, AF 2) is determined by an error projection on the basis of an additional deviation error (AF'), wherein the additional deviation error (AF') is determined for the geometric deviation of the satellite (RF1,..., RF4) relative to the receiver, on the basis of a context for the at least one system parameter, the context being previously determined and stored in the receiver, and wherein the error projection performs a transformation into a x-y-coordinate system of the receiver, and - a first and second value (AF 1, AF 2) of the error projection is determined, wherein - the first value (AF 1) for the at least one system parameter is determined on the basis of a first parameter value (s 1) of the additional deviation error (AF'), wherein the first parameter value (s 1) is determined depending on the geometric deviation on the basis of the stored context, - the second value (AF 2) for the at least one system parameter is determined using a modified parameter value (ms 1) of the additional deviation error (AF'), which is modified in comparison to the predetermined parameter value such that the second modified parameter value (ms 1) is determined depending on the geometric deviation from a modified context, which results from a linear displacement of the stored context, and the second modified parameter value is assumed more conservative in comparison to the first parameter value, wherein the more conservative assumption corresponds to a greater error of the system parameter, - the smaller of both values is used as deviation error (AF 1, AF 2).