For the downward continuation method of gravity field, the frequency domain continuation method has different requirements for data noise and continuation distance, and there is no clear conclusion yet. This paper analyzes seven frequency domain downward continuation methods, including Milne method, Taylor series expansion method, integral iteration method, Tikhonov regularization method, CGNR method, iterative least squares method, and Landweber iterative method. The model was tested using simulation data and aviation measured data, and the results were compared and studied. The results show that the Milne method and the Taylor series expansion method can be used for continuation of point distances less than 14 times under noise-free conditions; the integral iteration method has better stability when continuation of point distances 1 to 20 times without noise, but is more sensitive to noise; the Tikhonov regularization method has significant advantages when it contains noise and is greater than 5 times of point distances, and can obtain higher accuracy; the CGNR method, iterative least squares method and Landweber iterative method have wide applicability, and can maintain high accuracy when continuation of point distances 1 to 20 times under different noise conditions. Among them, the noise resistance of the Landweber iterative method is the most outstanding, and the latter four methods show certain advantages in actual data experiments, and can obtain stable downtime results.
| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |