Tin:Triangulated irregular network.
A surface representation derived from irregularly spaced sample points and breakline features. The TIN dataset includes topological relationships between points and their neighboring triangles. Each sample point has an x,y coordinate and a surface or z-value. These points are connected by edges to form a set of nonoverlapping triangles used to represent the surface. TIN is also called an irregular triangular mesh [三角网]or an irregular triangular surface model.

grid: (规则矩形格网)
A geographic representation of the world as an array of equally sized square cells arranged in rows and columns. Each grid cell is referenced by its geographic x,y location. See raster.

DEM: Digital elevation model.
A digital representation of a continuous variable over a two-dimensional surface by a regular array of z-values referenced to a common datum. Digital elevation models are typically used to represent terrain relief. Also referred to as digital terrain model (DTM).
An elevation database for elevation data by map sheet from the National Mapping Division of the U.S. Geological Survey (USGS)[美国地质调查局]. The format of the USGS digital elevation datasets.

1.tin 和 grid是DEM的两种表面模型,前者是矢量,后者是栅格.

2.数字高程模型（digital elevation model）。地形模型不仅包含高程属性，还包含其它的地表形态属性，如坡度、坡向等。dem通常用地表规则网格单元构成的高程矩阵表示，广义的dem还包括等高线、三角网等所有表达地面高程的数字表示。在地理信息系统中，dem是建立数字地形模型（digital terrain model）的基础数据，其它的地形要素可由dem直接或间接导出，称为“派生数据”，如坡度、坡向.

3.DTM英文全名：Digital Terrian Module 数字地形模型。是地形地表属性信息（如高程、坡度、坡向）的数字表达，是带有空间特征信息和地形属性特征信息的数字描述。
DEM英文全名：Digital Elevation Module 数字高程模型。是地形属性信息为高程的数字地形模型。通过空间分析可以派生出数据。在地理信息系统里面，DEM可以生成其他类型的DTM，并且DEM包括了规则网格模型Grid,不规则三角网模型、等高线模型

4.空间插值——空间插值常用于将离散点的测量数据转换为连续的数据曲面，以便与其它空间现象的分布模式进行比较，它包括了空间内插和外推两种算法。空间内插算法：通过已知点的数据推求同一区域未知点数据。空间外推算法：通过已知区域的数据，推求其它区域数据