Pitney Bowes MapInfo Vertical Mapper - Manual (Page 153)

Chapter 8: Using the Grid Tools
User Guide
151
Splicing Grids Together
The Grid Splicer tool combines one or more grids into a single grid file. There are two distinct ways
in which grids can be spliced together: merging and stamping. The difference lies in how each of
these procedures handles the values of grid cells that overlap other grid cells.
In merging, two or more grids are combined, and where they overlap a mathematical calculation is
performed to determine the new grid value. Only numeric grids can be merged. You can choose
from five calculation methods: Average, Minimum, Maximum, Average (Min, Max) (average of the
minimum and maximum values), or Median, where Average is the default. Therefore, if two grids are
merged using the Average calculation, and where the first grid has cells with the value of 20 and the
second has cells with the value of 10, then any overlapping areas will have cells with the value of 15
in the resulting grid (next figure). Merging is often used when several grid tiles cover a study area
that needs to be combined into a single grid, or when you want to create a grid that has the
highest/lowest value of all the input grids. Null values contained in any of the grids being processed
are ignored.
In the areas where Grid 1 (value of 10) and Grid 2 (value of 20) overlap, the resulting
grid will have a value of 15 when the Average overlap calculation is chosen.
In stamping, two or more grids are combined, and where they overlap, the values of one of the input
grids will overwrite the values of the other. You can stamp both numeric and classified grids, but
grids can be stamped only with a grid of similar type. It is not possible to stamp a classified grid with
a numeric or vice versa. Stamping is usually performed when you need to update areas of a grid, for
example, updating a land use grid with the area of a new subdivision or an elevation grid with
building heights. Null values contained in any of the grids being processed are ignored.
Depending on which grid is the reference grid and the order in which the input grids
are listed, different results will be obtained. On the left, Grid 2 is being stamped on Grid
1. Therefore the cell values of Grid 2 will override the values of Grid 1 in the resulting
grid. On the right, Grid 1 is being stamped on Grid 2. Therefore the cell values of Grid
1 will override the values of Grid 2 in the resulting grid.