# How TIN To Raster (3D Analyst) works

TIN To Raster converts a triangulated irregular network (TIN) to a raster through interpolation. Every cell in the output is assigned a height or NoData value depending on whether or not the cell center falls within the TIN's interpolation zone.

The data type of the output raster is set with the Output Data Type. It can be either FLOAT or INT. FLOAT, which is the default, outputs single-precision floating point values. INT outputs signed long values. FLOAT can preserve heights with decimals. INT is useful when whole number output is permissible because some output formats (for example, ESRI Grid) can benefit from compression using this data type.

The Method determines the interpolation used. It can be LINEAR or NATURAL_NEIGHBORS. Linear interpolation views TIN triangles as planes. Each output cell is assigned a height by finding which triangle, in 2D space, it falls in and evaluates the position of the cell center relative to the triangle plane. Natural neighbor interpolation produces a smoother result than linear. It uses an area-based weighting scheme on the closest TIN nodes found in all directions around each output cell center. Hard breaklines in the TIN will influence the result as the natural neighbor surface is not continuously smooth across them.

The Sample Distance variable represents the output cell size and is defined in one of two ways. The OBSERVATIONS keyword is followed by an integer that indicates the number of columns desired in the output. The cellsize is determined based on the output extent and number of columns. By default, OBSERVATIONS 250 is used. To provide an explicit cell size, use the CELLSIZE keyword followed by the desired size, which can be given as a floating point number.

The Z Factor variable is used to convert the z-units of the output raster. The output heights are multiplied by this value. A default Z Factor variable is calculated to convert the z-units to the same unit of measure as x,y if, and only if, x-, y-, and z-units are defined in the spatial reference of the input TIN and are standard projected units (for example,. meters, feet). If x-, y-, and z-units are the same, a value of 1.0 is used. If any of the units are undefined, a value of 1.0 is used.

When there's no output extent defined in the geoprocessing analysis environment, the extent is calculated from the TIN, ensuring the entire data area is covered by the output raster. In this calculation, the lower left origin of the TIN, based on its rectangular extent, is used as the cell center of the lower left raster cell. Most raster description tools use the outer cell boundaries to describe extent, rather than cell centers, so it may appear the output raster's extent exceeds that of the input TINs. When there's an output extent defined, the TIN To Raster tool uses the origin of the specified extent as the lower left cell boundary for the output raster. This is for consistency of behavior with other raster tools and facilitates use of a snap raster. The X and Y max values of the output raster are then determined by using the origin plus the cellsize specified in the TIN To Raster tool to see how many rows and columns fit within the user-specified extent. Therefore, the actual X and Y max values of the output might not exactly match the user-defined values if width or height of extent is not evenly divisible by cellsize.

6/10/2013