def METHOD_NAME(self, ch, value):
    '''scale a channel to 1000/1500/2000'''
    v = value/10000.0
    if v < -1:
        v = -1
    elif v > 1:
        v = 1
    if ch == 3 and self.mpstate.vehicle_type != 'rover':
        if v < 0:
            v = 0
        return int(1000 + v*1000)
    return int(1500 + v*500)