A mould system for moulding a blade shell of a wind turbine blade, the mould system comprising a first mould for manufacturing a first blade shell part of the wind turbine blade and a second mould for moulding a second blade shell part of the wind turbine blade, the first mould having a first moulding side with a first moulding surface that defines an outer shape of the first blade shell part, the second mould having a second moulding side with a second moulding surface that defines an outer shape of the second blade shell part, the mould system being configured to rotate and position the first mould such that the first moulding side is facing the second moulding side and such that the first blade shell part may be joined with the second blade shell part so as to form the blade shell of the wind turbine blade, the first mould comprising a first mould flange along at least a part of the periphery of the first moulding surface, the first mould flange being configured to provide a first shell part flange along at least a part of the periphery of the outer shape on the first blade shell part, the mould system comprising one or more fastening elements (140, 140', 140") attachable to the first mould and being configured to secure the first blade shell part to the first mould during rotation and positioning of the first mould, the one or more fastening elements including a first fastening element being configured to secure the first blade shell part to the first mould at a first fastening position along the first mould flange, the mould system comprising a measurement arrangement comprising one or more measurement units (150, 150', 150", 150′′′) including a first measurement unit, wherein the measurement arrangement is configured to measure displacement of the first shell part flange relative to the first mould flange, wherein the first measurement unit is configured to measure displacement of the first shell part flange relative to the first mould flange at a first measurement position along the first mould flange. comprising a first mould for manufacturing a first blade shell part of the wind turbine blade and a second mould for moulding a second blade shell part of the wind turbine blade, the first mould having a first moulding side with a first moulding surface that defines an outer shape of the first blade shell part, the second mould having a second moulding side with a second moulding surface that defines an outer shape of the second blade shell part, the mould system being configured to rotate and position the first mould such that the first moulding side is facing the second moulding side and such that the first blade shell part may be joined with the second blade shell part so as to form the blade shell of the wind turbine blade, the first mould comprising a first mould flange along at least a part of the periphery of the first moulding surface, the first mould flange being configured to provide a first shell part flange along at least a part of the periphery of the outer shape on the first blade shell part, the mould system comprising one or more fastening elements (140, 140', 140") attachable to the first mould and being configured to secure the first blade shell part to the first mould during rotation and positioning of the first mould, the one or more fastening elements including a first fastening element being configured to secure the first blade shell part to the first mould at a first fastening position along the first mould flange, the mould system comprising a measurement arrangement comprising one or more measurement units (150, 150', 150", 150′′′) including a first measurement unit, wherein the measurement arrangement is configured to measure displacement of the first shell part flange relative to the first mould flange, wherein the first measurement unit is configured to measure displacement of the first shell part flange relative to the first mould flange at a first measurement position along the first mould flange.