10 - Gridding and Contouring
Isochron Calculations
Select Horizon, Horizon Calculation, Select all lines and
create a formula for NRDG minus DNVG.
Call the output nrdg-dnvg to subtract the Nordegg surface
from the Dunvegan Beaverhill lake surface calling the output bvlk-irtn.
Change the map attributes active horizon to display this isochron
Display this map with a color bar. Notice how this isochron thickens
from the Northwest to the Southeast.
Grid Parameters
Select (Horizon), (Grid) and (Contour)
If the program beeps because there are too many grid cells, we need to set up
a polygon to constrain our grid.
Grid within User Defined Polygon
Our map is too large and contains too many grid cells. This can easily be
corrected by creating a polygon around the area to be gridded.
Change (Action) to (Draw Poly line). Draw a line clockwise and double click on the last point to close the polygon. Save the layer GridPoly. This is how easy it is to edit culture in SeisX!
In map gridding select polygon named GridPoly and be sure to hit the include
button 
If the are large gaps in the gridding, you may need to go into detailed
gridding parameters and increase the Maximum gridding distance.
Check the line intersections and correct interpretation problems. Repeat and
check other important isochrons.
Edit Grid Contours
Our map is now gridded and contoured. Contours are now culture and can be
edited with the SeisX culture editor. Select the nrdg-dnvg and Set layer to
Active, select Edit Object
Delete points with the middle mouse button. Points can be shifted or inserted
using the left mouse button. Try it out. The right mouse button will accept the
new changes. Click on another object and try editing it. There is also a move
option that will move a whole object, useful for moving a defined fault from
one horizon to another horizon. The contour highlighted in yellow to the right
iscurrently being edited.
Color Fill
Select Map Attributes and change the Ribbon Display to and the Active Grid to
. Press Apply to update the map.
A map in SeisX is colored for each grid cell. While somewhat unconventional, I find that the colored grid blocks provide another form of visualization for a set of gridded data points. This display technique is useful for stratigraphic interpretation.
This isochron demonstrates the regional thinning to the North West.
Note: click on any screen picture and you will have the full size image. Press (Alt) and the left arrow and you will return to the document.
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