The indoor complicated environment can interfere with the geomagnetic field and then affect on angle observation precision of magnetic compass. As a constant source of interference will form a relatively stable interference magnetic field environment

it can establish a magnetic declination error fingerprint database

and compensate on error of magnetic compass by differential method.A generalized extension approximation method is proposed to process the magnetic declination of the sampling area

and the angle is compensated by using differential processing. Experiments show that

the proposed algorithm can improve the average precision of the angle from ± 8° to within ± 0. 2° by compensation. In indoor integrated positioning applications

the average positioning precision is 0. 82 m

the positioning error of 96. 5 % probability within 2 m

so it can achieve the precision of sub-meter positioning.