How can i clip this TIN and form like the polygon.
Best Answer
Use the Delineate Tin Data Area tool (in 3D Analyst tools / Data Management / Tin) to get rid of those nasty long triangles in the no data areas of the tin. Choose a distance more than your data spacing and use the options "PERIMITER ONLY".
Firstly you need to understand that contours are not painted on the ground, they are a model. Secondly a TIN and a DEM are also models. With that in mind debating the relative inaccuracies of models of a model seems a little pointless.
When creating a contour from a TIN the process must internally convert to a raster or the only vertices created will be on the facets (lines joining nodes in the triangulation), the cell size used by this process is arbitrary, which is then contoured in the same manner as if you converted it to a raster yourself. In truth the answer lies in the cell size that is arbitrarily chosen by the process and the TIN to raster method, which you are unlikely to know.
If you want to know what the difference is then convert both contours to TIN, TIN to raster and then subtract one from the other, view this against the points you started with and you will find that the differences between both contours are least where there is a TIN node and most where there is significant distances between nodes, this is where interpolation occurs and whatever is happening here is subjective!
Best Answer
Use the Delineate Tin Data Area tool (in 3D Analyst tools / Data Management / Tin) to get rid of those nasty long triangles in the no data areas of the tin. Choose a distance more than your data spacing and use the options "PERIMITER ONLY".