Join strings
This function is an alternative method for saving the data in the active layer to a string (.str) file. It is designed to create a string file in which the following rules apply:
- any string number may have at most one open segment
- any string number which has more than one segment must consist only of closed segments.
To run this function: Choose File > Save > Join strings, or...
Note: Do not use Join Strings to save a DTM or 3DM (solid). DTM and 3DM data must be saved using the Save File function.
The process of joining the strings involves specifying a join distance which is used as a tolerance for the gap between the ends of all open segments of a string. If multiple open segments of a string exist and the end points of all these open segments are within the join distance of the end of another segment then it may be possible to create a set of closed segments for the string or one open segment. The joining operation may not always be able to provide an unambiguous join for the open segments. In this case you are advised of the problem via a message in the message window and you will either have to try with a new join distance or abort from the Join Strings function and carry out further editing before attempting to join the strings again.
Many ambiguous situations may arise when trying to join string segments which can make it difficult or impossible to successfully join the segments. If this happens you can always save the data by using the Save File function. The join distance may have any value between -1 and 999999. The value of -1 is special in that it instructs the Join Strings function that the string is not to be considered for joining according to the rules above, and all segments in the string are to be joined together in whatever order they exist in memory. The -1 value is often used by surveyors to join spot-height strings.
Although the join distance may take on almost any value you should attempt to use as small a join distance as possible. The general rule to observe is that the larger the join distance the more difficult it is to successfully join the segments together unambiguously.
You can also join pairs of segments by using Edit > Segment > Join.
Note: The data which is held in memory is not altered. The modified strings are only written to a new string file. If you want to view the new strings it is necessary
to recall the file which has been created.
Fields on the Join string segments and save to a file form
Layer
Display only. The name of the active layer from which the data are to be saved is displayed here.
Location and Id Number
Define the file which is to be created by entering the Location and Id Number for the file. The Join Strings function will always create a string (.str) file if it is successful.
Purpose
.str and .obs files contain a purpose field in the file header which is used to describe the contents of the file.
You may enter the purpose of the file here so that it is recorded in the file header.
String range
Enter the range of strings which are to be saved to the new file. If you leave this blank then all strings will be saved to the new file otherwise only the specified strings will be saved to the new file.
Complete the JOIN STRING SEGMENTS AND SAVE TO A FILE form and choose Apply to display the ENTER SEGMENT JOINING PARAMETERS form.
String
Display only. The number of the string which is being joined is displayed.
Join distance
Enter the join distance which is to be used to attempt to join the segments together.
For all strings
Respond with
- Y, to apply the join distance to all the strings which are to be joined together, or
- N, to apply the join distance to the displayed string number only. This form will appear again for the next string which has to be joined.
(C)lockwise or (A)nticlockwise
Respond with:
- C, means that all the segments have to be made clockwise in direction, or
- A, means that all the segments have to be made anti-clockwise in direction.
Result
The data in the active layer is written to the specified file. If the file already exists then you will be prompted to confirm the save with a verification form to prevent accidental overwriting of the existing file.
Messages
String xxx - status = yyy
This is to inform you of the status of string number `xxx'. The status value `yyy' may be either open or closed.
String xxx segment yyy is closed direction is zzz
This message is displayed to tell you about the direction of string number `xxx' segment number `yyy'. The direction `zzz' will be either made clockwise, made anti-clockwise or unchanged.
String xxx is an open string
String `xxx' has been saved as an open string.
String xxx is a spot height string
You specified a join distance of -1 for string number `xxx' and it was saved as a single segment of spot height points.
xxx points stored on file yyy
The file named `yyy' has been successfully created with `xxx' points in it.
Warning
No strings in memory - Cannot join strings
An attempt to join string segments together has failed because there are no strings to be joined.
Can't join segment 1 of string 1
The ENTER SEGMENT JOINING PARAMETERS form is re-displayed. Enter a larger join distance or choose Cancel and join the segments manually.
There are a number of ways to manually join strings, for example you may use the SEGMENT Join or POINT Move functions from the Edit menu.