Intersections
Use the Tie Line Levelling > Intersections menu option (geogxnet.dll(Geosoft.GX.Levelling.Intersections;Run))* from the Geophsyics Levelling extension to create an intersections table. Difference statistics on intersections deviations can be calculated and saved to an output file.
Intersections dialog options
Application Notes
If the X & Y channels are not assigned in the active database, run Set Coordinate System to set the current X & Y channels and then run this tool again.
The first step in leveling tie lines and regular survey lines is to produce a tie line intersections table or database.
Intersections Table Format (*.tbl)
The output intersections table file tabulates every intersection between tie lines and regular survey lines. It includes the exact ground location of the intersection point, the tie line and survey line numbers, the recorded value on each line, and the horizontal gradient of the data at that location.
Example of an intersection table:
/ Intersection Table// X Y Tie# TFid TZ TDZ Line# LFid LZ LDZ8094.09 5336.51 90 1306.97 64180.2 0.068 470 574.133 64197.8 0.4638106.99 1893.43 90 1409.55 64207.2 0.445 471 2276.95 64266.1 0.2118049.27 7721.71 90 1030.20 64069.9 0.556 510 599.391 64065.8 0.1558082.4 6688.47 90 1170.74 64116.5 0.421 490 2304.9 64130.0 0.5267983.82 0078.85 90 777.000 64078.9 0.558 550 649.575 64069.6 1.3768058.46 7854.91 90 876.391 64050.9 0.132 530 2282.74 64075.1 0.0097997.32 2392.99 90 472.451 63904.9 0.759 590 881.501 63852.4 1.427
If the intersection tolerance is greater than 0.0, the points of closest approach within the tolerance will also be recorded, where lines do not actually intersect. The location will be the average of the closest points on each line.
The columns of the table:
X
X coordinate of the intersection
Y
Y coordinate of the intersection
Tie#
Tie line number
TFid
TZ
Tie line reading
TDZ
Tie line gradient (per fiducial)
Line#
Line number
Lfid
Line fiducial
LZ
Line reading
LDZ
Line gradient (per fiducial)
Intersections Database (*.gdb)
The Geosoft database can be used to store the intersections information. This has several benefits:
1. The exact intersections locations can be plotted to a map using the normal mapping and symbol methods.
2. Quantities such as the mis-tie or gradient values can be easily gridded for display.
3. Intersections are sorted by Tie Line, instead of appearing as a single long list.
To create an intersections database, simply run the Levelling Intersections GX and specify a file of type (*.GDB) as the output intersection table. The XLEVEL GX recognizes both the original *.tbl file format and the new Geosoft Database file as inputs. Each Tie in the intersection table gets its own line in the Geosoft Database file, containing all the line intersections with that tie line.
The channels of the intersections database:
X
X coordinate of the intersection
Y
Y coordinate of the intersection
TIE
Tie line number
TIE_FID
Tie line fiducial.
TIE_LEVEL
Tie line reading.
TIE_GRAD
Tie line gradient (per fiducial).
LINE
Line number.
LINE_FID
Line fiducial.
LINE_LEVEL
Line reading.
LINE_GRAD
Line gradient (per fiducial)
Intersection_dX
Difference (at each intersection) between the closest X along the survey line and the closest X along the tie line.
Intersection_dY
Difference (at each intersection) between the closest Y along the survey line and the closest Y along the tie line.
Intersection_dDist
Distance (at each intersection) of the intersection deviations, calculated as:
Intersection_dData
Difference (at each intersection) between the closest data reading along the survey line and the closest data reading along the tie line.
CROSS_DIFF
Miss-tie value (LINE_LEVEL - TIE_LEVEL). Note that when the XLEVEL GX is used to extract mis-tie values to the flight database using the "Level Lines" option, the resulting CROSS_DIFF values in the flight database are of the opposite sign, i.e. TIE_LEVEL - LINE_LEVEL.
Intersections Statistics File
The following difference statistics (minimum, maximum and standard deviation values) on the survey/tie line intersection deviations are calculated and reported in the output file:
Min
Max
StdDev
X_Position
Intersection_dX_min Intersection_dX_max Intersection_dX_Dev Y_Position
Intersection_dY_min Intersection_dY_max Intersection_dY_Dev Distance
Intersection_dDist_min
Intersection_dDist_max
Intersection_dDist_Dev
Data
Intersection_dData_min
Intersection_dData_max
Intersection_dData_Dev
The XLEVEL GX can be used to extract levelling corrections from the intersection table.
The STATLEV GX and the FULLLEV GX can then be used to apply the levelling corrections to the data.
*The GX tool will search in the "...\Geosoft\Desktop Applications \gx" folder. The GX.Net tools, however, are embedded in the geogxnet.dll located in the "...\Geosoft\Desktop Applications \bin" folder. If running this GX interactively, bypassing the menu, first change the folder to point to the "bin" folder, then supply the GX.Net tool in the specified format.
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