When you work with overlay maps, you will be working with one or more of the following:

• File set for pointnodes
• File set for lines
• File for graphic characteristics specifications

To save a file for an overlay map, choose Save from the File menu, and choose the appropriate item (Pointnodes, Lines, or Graphic Characteristics) from the cascading menu.

(NOTE: If you have not added or edited any pointnodes, lines, or graphic characteristics, the Save item will be unavailable ("grayed-out"). Save only becomes available when you have something to save. The same is true for the items in the cascading menu.)

The File Save window will pop-up.

The File Save window contains the following:

• At the top is the name of the current directory. This is also a menu button, which you can press to get to any higher directory.
• On the left are the directories in the current directory.
• On the right are the files in the current directory.
• At the bottom is the Selection box. You may type your selection in the box, or simply click on a directory or file.

To open a directory, click on the directory name, then click Save, or just double-click on the directory name. Alternatively, you may point at the Selection box and type in the directory name before clicking Save.

To save a file, point at the Selection box and type in the file name before clicking Save. Alternatively, to overwrite an existing file, click on the file name, then click Save. (To prevent a misguided click from overwriting the wrong file, double-clicking is disabled for saving files.)

The file will be saved, and File Save window will close.

What name should you give your file?

Filenames should begin with a letter or a digit ('a'-'z' or '0'-'9'). Hyphens ('-'), underscores ('_'), and periods ('.') may also be used, but not as the first character.

Pointnodes and lines are saved in .shp files, so the name must end with the ".shp" extension. Graphics characteristics should be saved with a name that has a ".gchar" extension. (If you are nostalgic about three-letter filename extensions, you could use ".gch", but ".gchar" is preferred.)

Strictly speaking, .shp files are supposed to be limited to eight characters before the ".shp" extension (e.g., "abcdefgh.shp"), have only the single period ('.'), and be all lower case. You may choose to follow those rules, but XViewSDTS does not enforce them.

Because .shp files can hold pointnodes or lines, some people like to use a certain convention to identify the type of objects in the file. In our examples we use names ending in "n.shp" for files that hold pointnodes, and names ending in "l.shp" for lines. (Why not 'p' for pointnodes? We plan to use 'p' for polygons in the future.) You can use whatever works for you, or nothing at all, as long as you know what's in the files.

When you create a file for pointnodes or lines, you are actually creating a set of three files.

Type	Used for
.shp	pointnode & line coordinates
.prj	projection for coordinates
.dbf	pointnode & line attributes

You do not need to specify the names of the .prj or .dbf files when saving or opening files, nor should you attempt to. They will be given the same base filename as your .shp file, and will be saved and opened automatically.

This bears repeating, for it can be confusing. When you save a .shp file, you are saving a set of three files (.shp, .prj, and .dbf), but you will only be using the name of the .shp file. The same is true for opening files. Think of the other two files as extensions of the .shp file.

After opening or saving a file, when you go to save it again the File Save window will open to the directory in which you previously saved it, and its name will already be in the Selection box. You need only to click Save.


You are reminded that the file set already exists. (If you had intended to save your modifications to a new file, you have been given a second chance to do so: answer No and type in a new name.) To update the existing file set click Yes.

Copyright © 2005 by Dapper Mapper