Contour map – April 6, 2023 at 07:51AM

Hello, I’m currently doing my bachelor’s thesis and need help on doing a contour map on soil layer’s thickness. I’m working with “Surfer” and “QGIS”. So far I’ve managed to do a contour map using natural neighbor gridding method which only interpolates data between data points but I need to extrapolate it too since my data points in research area doesn’t cover it all (see photos). My research area is between a meandering river and a curving road and I only need this area to contain contours. I have no experience working with those programs so much advice is needed. Thank you in advance.

My research area and data points. I want to only fill this research area with contours.

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Layer thickness contour map made with natural neighbor gridding method and with logarithmic level method.