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brady71

Surfer 8 contour map constricting of isobars at sample locations

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Not sure if Surfer 8 is still supported, but I thought I would take a shot. I am trying to make depth contour plots of oceanographic data (in this case, temperature)along a 1700 km transect. We conducted 8 vertical profiles along this transect. When making a contour plot in Surfer 8 the isobars tend to constrict at the actual sampling locations, giving the transition in temperature an unrealistic appearance. The gridding method that gives me the best result is the triangulation with linear interpretation. I have smoothed the data to the nest of my knowledge. Is there some advanced function that will allow me to smooth the transition between isobars when approaching experimental stations? Thanks in advance for any support.

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Hi brady71,

Use anisotropy to weight the horizontal direction preferentially. Refer to the Anisotropy topic in the help file for an example of the benefits of using anisotropy for an oceanographic profile where the horizontal distance is much greater than the vertical distance.

surfer8anisotropy2.jpg

The plot on the left uses the same weighting in the horizontal and vertical directions.

The plot on the right shows the benefits of anisotropy or different weights in the horizontal and vertical directions.

From the Surfer 8 Help file topic on Anisotropy.

Different gridding methods specify the anisotropy differently, but all access this feature from the Advanced Options button in the Grid Data dialog box. For Kriging, click on the Edit button in the Kriging Advanced Options dialog box to get to the anisotropy options.

Thanks,

Tom B

RockWare Inc

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Thanks, Tom

That helped to a degree. I am attaching a map of ocean temp with depth along a 1700 km transect. The grid was generated using Kriging, Linear, Anistropy ratio of 50. It looks pretty good, but the temp. changes at Y-axis 600 and ~1500 still seem too abrupt. Could this also be a scaling issue? Thanks for your help.

brady

brady71anisotropysurfer.jpg

post-10599-085496100 1345490599_thumb.jpg

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Hi Brady,

Scaling is the issue that anisotropy attempts to resolve. A lower anisotropy ratio may help with the abrupt near-surface changes from left to right.

You may want to overlay a post map with the original data values to see if a less abrupt change is reasonable.

Thanks,

Tom B

RockWare Inc

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