Hawth's Analysis Tools for ArcGIS

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 Summary

CREATE VECTOR GRID TOOL
Input: a reference layer (a feature or raster layer), or a set of bounding coordinates (XMin, XMax, YMin, YMax)
Output: a line or polygon layer representing a regular grid
Features:

  • allows the user to create polygons or lines as the output feature type
  • allows the user to snap the grid to major coordinate system intervals (e.g. the lines will occur on the 1000 meter marks on the UTM grid)
  • allows different spacing intervals in the X and Y axes
  • output lines are coded with a LABEL field that contains the coordinate of the line (useful for creating a graticule for a printed map)
  • output polygons contain four fields that contain the Min/Max X/Y values for each polygon

Limitations:

  • None known


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 Example

Figures A-D. The first example (A) shows a regular 1000m grid created based on the extent of a reference raster layer. The second example (B), is the same reference layer, but the grid is now snapped to the major coordinate system interval (the 1000m marks on the UTM grid). The ability to label lines for map production is shown in C. And finally, the ability to generate a grid with unequal X and Y intervals is demonstrated in D (a polygon shapefile).

 Help

Getting started. It is advisable to decide what will define the extent of the vector grid before you start the tool. This can either be a feature or raster layer, or a set of coordinates that you manually type in. Note that for reference layers, the extent is considered to be the rectangle that bounds the layer.

Lines or polygons as output? For map production purposes, using lines as the ouput feature is likely to be the most useful because a LABEL field is added to the attribute table and coded with the appropriate coordinate for graticule labeling (the X coordinate for vertical lines, and the Y coordinate for horizontal lines). For tiling datasets or for spatial analysis purposes, the polygon output is likely to be most apprpriate.

How does the snapping work? If you opt to snap the grid to major coordinate system intervals, the tool will use the interval you specify to determine where the snap should occur. For instance, if you use an interval of 1000m, the grid will be snapped to the 1000m mark of the UTM grid. If you use an interval of 10m the grid will be snapped to the 10m marks of the UTM grid. For uneven intervals like 2045.67, the tool will look at the number of significant digits (SD) before the decimal place (in my example 4), and snap the grid to the first major interval defined by:
1 x 10 ^ (SD-1)
which in my example is 1000.

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