scholarly journals VARMAG; a Fortran program to implement the variable-magnetization terrain-correction method for aeromagnetic data

1986 ◽  
Author(s):  
V.J. Grauch
Keyword(s):  
Correction Method ◽  
Fortran Program ◽  
Terrain Correction ◽  
Aeromagnetic Data

A new variable‐magnetization terrain correction method for aeromagnetic data

Geophysics ◽  
1987 ◽  
Vol 52 (1) ◽  
pp. 94-107 ◽  
Author(s):  
V. J. S. Grauch
Keyword(s):  
Magnetic Field ◽  
Real Data ◽  
Theoretical Models ◽  
Correction Method ◽  
Terrain Correction ◽  
Aeromagnetic Data ◽  
San Juan Mountains ◽  
Terrain Effects ◽  
Terrain Corrections ◽  
Lake City

Terrain effects in aeromagnetic data are produced by rugged, magnetic topography. These effects mimic the shape of topography and can often be so large that they obscure anomalies of interest. Thus it is desirable to remove terrain effects from aeromagnetic data in order to isolate the anomalies to be investigated. However, removal of aeromagnetic terrain effects has been a longstanding problem. Previously developed methods have succeeded only in certain, specific geologic situations. I present a new aeromagnetic terrain‐correction method that is superior to the previously developed methods for the general case. This method takes into account the highly variable magnetic properties of rocks and can remove terrain effects whether the sources of interest are shallow or deep. The new method is based on the assumption that magnetic sources of interest are often geometrically unrelated to terrain. It finds the magnetization that gives a magnetic‐field residual with minimum correlation to terrain effects for a window of data within a grid of magnetic‐field values. By repeating the calculation for windows covering the entire grid, a grid of variable‐magnetization values is produced which is combined with topography to calculate a magnetic‐terrain correction. The variable‐magnetizaton method was extensively tested using theoretical models (where the answer is known) and using real data from the Lake City caldera area in the San Juan Mountains of southern Colorado. The tests demonstrated the method’s effectiveness in removing terrain effects from aeromagnetic data. Valid terrain corrections were not obtained where anomalies of interest correlated with terrain effects. However, these places are readily recognizable and easily corrected by editing some of the magnetization values.

scholarly journals Micro-Topography Mapping through Terrestrial LiDAR in Densely Vegetated Coastal Environments

2021 ◽  
Vol 10 (10) ◽  
pp. 665
Author(s):  
Xukai Zhang ◽  
Xuelian Meng ◽  
Chunyan Li ◽  
Nan Shang ◽  
Jiaze Wang ◽  
...  
Keyword(s):  
Correction Factor ◽  
Laser Scanning ◽  
Accuracy Assessment ◽  
Correction Method ◽  
Terrain Correction ◽  
Surface Model ◽  
Coastal Environments ◽  
Terrestrial Lidar ◽  
Dense Vegetation ◽  
Micro Topography

Terrestrial Light Detection And Ranging (LiDAR), also referred to as terrestrial laser scanning (TLS), has gained increasing popularity in terms of providing highly detailed micro-topography with millimetric measurement precision and accuracy. However, accurately depicting terrain under dense vegetation remains a challenge due to the blocking of signal and the lack of nearby ground. Without dependence on historical data, this research proposes a novel and rapid solution to map densely vegetated coastal environments by integrating terrestrial LiDAR with GPS surveys. To verify and improve the application of terrestrial LiDAR in coastal dense-vegetation areas, we set up eleven scans of terrestrial LiDAR in October 2015 along a sand berm with vegetation planted in Plaquemines Parish of Louisiana. At the same time, 2634 GPS points were collected for the accuracy assessment of terrain mapping and terrain correction. Object-oriented classification was applied to classify the whole berm into tall vegetation, low vegetation and bare ground, with an overall accuracy of 92.7% and a kappa value of 0.89. Based on the classification results, terrain correction was conducted for the tall-vegetation and low-vegetation areas, respectively. An adaptive correction factor was applied to the tall-vegetation area, and the 95th percentile error was calculated as the correction factor from the surface model instead of the terrain model for the low-vegetation area. The terrain correction method successfully reduced the mean error from 0.407 m to −0.068 m (RMSE errors from 0.425 m to 0.146 m) in low vegetation and from 0.993 m to −0.098 m (RMSE from 1.070 m to 0.144 m) in tall vegetation.

scholarly journals AN IMPROVED SAR RADIOMETRIC TERRAIN CORRECTION METHOD AND ITS APPLICATION IN POLARIMETRIC SAR TERRAIN EFFECT REDUCTION

2013 ◽  
Vol 54 ◽  
pp. 107-128 ◽  
Author(s):  
Peng Wang ◽  
Qin Ma ◽  
Jinfei Wang ◽  
Wen Hong ◽  
Yang Li ◽  
...  
Keyword(s):  
Correction Method ◽  
Terrain Correction ◽  
Polarimetric Sar ◽  
Terrain Effect
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