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 open a file that you have previously created for an overlay map, choose Open from the File menu, and choose the appropriate item (Pointnodes, Lines, or Graphic Characteristics) from the cascading menu.

(NOTE: Open is for overlay maps only. To load base map surfaces, use the Load . . . items in the right-button menu, or Go GNIS in the View menu. See Getting Around for details.)

Normally, the File Open window will then pop-up.

If, however, you were editing a file and had neglected to save it before you chose Open from the File menu, you may get a question like this:

You should heed this warning.

Unless you really don't care to save any work that you have done on your lines since the last time you saved them, you should answer No.

After clicking No, the question window goes away, and you should save your file.

After saving your file you may again choose Open from the file menu.

The File Open window will pop-up.

The File Open 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.
• At the bottom right is the Read-Only toggle button, which you should click if you just want to look at the file without editing it.

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

Similarly, to open a file, click on the file name, then click Open, or just double-click on the file name. Alternatively, you may point at the Selection box and type in the file name before clicking Open.

Normally, the file will be loaded, and File Open window will close.

If you do something unexpected, like attempting to open a file of the wrong type, you will get an error message such as this:

In this case, Lines were chosen from the File Open menu, but the selected file contains pointnodes.

There are lots of "unexpected" things that you might do. For instance, if you are attempting to open a file of lines, but select a file that isn't even a .shp file, you will get a message of "Unsupported Format. . .". Showing all possible error messages here would be a bit tedious, so we won't.

If you wish to open a pointnode file or line file for editing, the current coordinate system needs to be the same as the one used when you created the file. However, if you only want to view the file, you may open it in Read-Only mode (by clicking the Read-Only button in the File Open window, before clicking Open).

Since you would normally open a file with the same coordinate system as the one you are using, XViewSDTS asks if you really want to do this.

Click Yes if that's what you want.

The file will be opened and its data reprojected. (Because you are in Read-Only mode, this will not alter the file itself.)

(Hint: Of course the current coordinate system should be a reasonable match for the file. For instance, if the current coordinate system is UTM zone 19, reprojecting a file that was created using UTM zone 18 may be reasonable, because it will introduce minimal distortion, but reprojecting a file that was created using UTM zone 10 will introduce significant distortion.)

Copyright © 2005 by Dapper Mapper