Split

This topic covers the Split interactive editing command that splits line and area objects using a cutting line.

 

 

The Split command uses a cutting line to cut existing areas and lines in a specified layer into parts, producing new objects, and transferring field values as desired into the resulting objects.  The cutting line can be a path drawn with the Draw Path tool, an existing line or area, or a new line or new area in the process of being created.  

 

Split is available in the right-click context menu for editing when drawing a path, when creating a new line or new area, or when an existing line or existing area is picked with an alt-click.   For example, begin drawing a new line that is to be used as a cutting line, and then right-click and chose Split to split all areas and lines the cutting line transects.

 

Options:

 

Example

Split makes it easy to divide areas or lines along a path into multiple areas or lines.  In the illustrations below we use a drawing that shows countries in Southeast Asia as polygonal area objects.   We draw a path to split the area representing the country of Vietnam into two areas.

 

Start by choosing Draw Path in the cursor mode button in the main toolbar.   Next, click as desired to draw a path that will be used to divide the area.  

 

 

Right-clicking anywhere and choosing Split in the context menu will pop open a Split dialog to allow us to choose how to divide attributes, the default being to copy attributes into the new parts that are created.   

 

By default, Split will divide all areas intersected from border to border by the path.  The Split dialog also provides a Use selection only check box that allows us to split only selected areas.

 

Pressing OK will split the area using the path.

 

 

The result is two new areas, divided exactly along the path line, by default copying attributes from the original area into both new areas.   If we would like to split attributes in different ways, for example, dividing a population field in the original area proportionately by the sizes of the new areas, we can choose that transfer rule in the Split dialog that pops open.  

 

Choices we make for splitting attributes will persist for that drawing in the same project session until changed again, to make repetitive operations fast and easy.

Summary

Editing with Split uses a simple workflow: select objects to be split, draw the path or object to use as a cutter, and apply the split.   The workflow works exactly the same way when splitting areas or lines.   We can split objects either in the same layer or in a different layer.

 

Split an area or line with a path:

 

  1. If desired, to split only selected objects, Ctrl-click to select the areas or lines that will be split by the path.

  2. In the cursor mode button in the main toolbar, choose Draw Path. Keyboard shortcut: Shift-T

  3. Draw the path that will be used as a cutting line.

  4. Right-click anywhere in the map and choose Split.  

  5. In the Split dialog that pops open, if there is more than one layer in the map, choose the layer containing objects to be split.

  6. In the Split dialog, choose rules for splitting attributes.  The defaults will copy values from the original objects into resulting objects.

  7. By default, all lines intersected by the path line and all areas the path line traverses from border to border will be split.  Check the Use selection only box, if desired, to split only selected objects.

  8. Press OK to apply the split.    Press Cancel to abandon the split.    

 

 Pressing OK is a command to apply the split and cannot be undone.

 

We can also use Split to split objects using an existing line or area, or by starting to draw a new line or area and then applying Split.  

 

Split areas or lines with an existing line:

 

  1. If desired, to split only selected objects, Ctrl-click to select the areas or lines that will be split by the line.

  2. Alt-click the line that will be used as a cutting line.

  3. Right-click anywhere in the map and choose Split.  

  4. In the Split dialog that pops open, if there is more than one layer in the map, choose the layer containing objects to be split.

  5. In the Split dialog, choose rules for splitting attributes.  The defaults will copy values from the original objects into resulting objects.

  6. By default, all lines intersected by the cutting line and all areas the cutting line traverses from border to border will be split.  Check the Use selection only box, if desired, to split only selected objects.

  7. Press OK to apply the split.    Press Cancel to abandon the split.    

 

Split areas or lines with a new line:

 

  1. If desired, to split only selected objects, Ctrl-click to select the areas or lines that will be split by the line.  

  2. In the cursor mode button in the main toolbar, choose Create Line.   Keyboard shortcut: Shift-L

  3. Draw the line that will be used as a cutting line, but do not save changes.     The line can be a complex, multibranched line, if desired.

  4. Right-click anywhere in the map and choose Split.  

  5. In the Split dialog that pops open, if there is more than one layer in the map, choose the layer containing objects to be split.

  6. In the Split dialog, choose rules for splitting attributes.  The defaults will copy values from the original objects into resulting objects.

  7. By default, all lines intersected by the cutting line and all areas the cutting line traverses from border to border will be split.  Check the Use selection only box, if desired, to split only selected objects.

  8. Press OK to apply the split.    Press Cancel to abandon the split.    

 

 

Split areas or lines with an existing area:

 

  1. If desired, to split only selected objects, Ctrl-click to select the areas or lines that will be split by the area.

  2. Alt-click the area that will be used as a cutting area.

  3. Right-click anywhere in the map and choose Split.  

  4. In the Split dialog that pops open, if there is more than one layer in the map, choose the layer containing objects to be split.

  5. In the Split dialog, choose rules for splitting attributes.  The defaults will copy values from the original objects into resulting objects.

  6. By default, all lines and areas intersected by the cutting area will be split.  Check the Use selection only box, if desired, to split only selected objects.

  7. Press OK to apply the split.    Press Cancel to abandon the split.    

 

 

Split areas or lines with a new area:

 

  1. If desired, to split only selected objects, Ctrl-click to select the areas or lines that will be split by the area.

  2. In the cursor mode button in the main toolbar, choose Create Area.  Keyboard shortcut: Shift-A

  3. Draw the area that will be used as a cutting area, but do not save changes.   The area can be a complex, multibranched area with holes and islands, if desired.

  4. Right-click anywhere in the map and choose Split.  

  5. In the Split dialog that pops open, if there is more than one layer in the map, choose the layer containing objects to be split.

  6. In the Split dialog, choose rules for splitting attributes.  The defaults will copy values from the original objects into resulting objects.

  7. By default, all lines and areas intersected by the cutting area will be split.  Check the Use selection only box, if desired, to split only selected objects.

  8. Press OK to apply the split.    Press Cancel to abandon the split.    

 

Automatic Decomposition to Shapes

Split is a visual command that cuts area or line objects where the path line crosses them, for lines intersecting any part of a line and for areas where the path line cuts from one area edge to another.   Normally, when doing interactive editing we work with drawings where what appear to be separate areas and lines are separate objects.  For example, in a map of countries, the contiguous mainland part of a country is one area object and the area shapes drawing islands that are part of the country are other area objects.  

 

Like other GIS packages, Manifold also allows area objects to consist of multiple branches, where what appear to be separate areas, like a mainland part of a country and various islands that are part of that country, are all a single, multibranched area object (also called a multipolygon in some GIS packages).  

 

When objects are created from multiple branches, for example, when what appear to be different areas are part of a single area object, that can lead to ambiguities as to whether a path cuts from one edge to another.  When what appear visually to be different areas are really different areas implies no such ambiguity.

 

To disambiguate such situations, all multibranched areas and lines that might possibly be involved in the Split are first decomposed into their constituent shapes and then the Split is performed.  That ensures that what was intended by the visual placement of the splitting path line across what appear to be independent area objects is what gets done in terms of a split.   If the Use selection only box has not been checked, all areas and lines with any part or branch falling within the bounding box of the path line will be decomposed into shapes, as possibly being involved in the split.   If the Use selection only box has been checked, only selected objects will be decomposed into their constituent shapes.  

 

The general rule of thumb is that doing interactive splits (or other interactive editing) on drawings full of multibranched area and line objects is unwise, since what look like separate objects are part of the same object.  That is fundamentally confusing.   It is best to first decompose to shapes all objects in a drawing and only then edit, when everything that looks like a separate object is indeed a separate object.

 

However, if we are editing a drawing that relies on multibranched objects, perhaps a world map where a single area is used to represent a country as well as all of the island parts and mainland parts of that country, we can still use Split to make edits: we simply must be aware that objects which are split or might be subject to a split will be decomposed into their constituent shapes.  The most orderly way of working in such situations is to always first select the targets of the split and then check the Use selection only box, so that only those objects are decomposed into shapes.  We can then do the split and then, if desired, merge the various resulting parts back into whatever arrangement of multibranched areas or lines we desire.

Example: Split an Area with a Path

We split the modern country of Vietnam into historical North and South areas, approximately using the 17th parallel as a cutting line.    We will use a map that has one drawing layer in it, called Countries, which shows world countries.

 

 

The drawing we will use is full of multibranched areas, also called multipolygons in some GIS packages, because it uses a single area object that has multiple branches to represent all of the different islands and other parts of a country.

 

 

For example, if we open the drawing's table, we can see there is only one record for Vietnam, even though a quick look at the map shows that there are islands that are just off the coastline that are part of Vietnam.    The table also shows us that there are various attribute fields, including a field for population.

 

 

With the focus on the open map window, choose the Draw Path tool in the cursor mode button in the main toolbar.

 

 

We draw a path that cuts across Vietnam approximately at the 17th parallel, the dividing line between North and South Vietnam during 20th century wars.

 

Right-click to launch the context menu.

 

 

Choose Split.

 

 

In the Split dialog, choose Countries as the layer containing areas to be split.   When we have only one layer in the map, that layer will automatically be chosen.

 

In the Split dialog, we leave copy as the default transfer rules for all fields but the Population_2020 field.  We double-click into the transfer rule cell for that field and choose split proportional as the transfer rule, so that the population value from the original object will be proportionately allocated to each resulting part based on the size of the part.

 

 

At this point we can still Cancel if we want to abandon the split.  Press OK to commit the split.

 

 

The area for Vietnam is split along the path line into two areas.  It is also split into individual shapes, that is, each island part that was formerly part of one big multibranched area object now has become a separate area object.   The path tool is cleared, ready to begin clicking a new path.

 

 

If we look into the drawing's table we see that new records have appeared for Vietnam.  The old record for Vietnam has been replaced by six records, with population values being proportionately allocated based on the relative sizes of each area object.  If we select the smaller records we can see where these records came from.

 

 

In the drawing window, we see the smaller records are area objects for islands that were part of the original, single, Vietnam area, which was a multibranched area (called a multipolygon in some GIS packages).   The Split process automatically decomposed the multibranched area into its constituent shapes, and then applied the Split by cutting the big area that represented the mainland into two large areas, cut at approximately the 17th parallel where we drew the path line.

 

 

If we scroll up in the table window, we see that the Thailand object has also been decomposed into constituent shapes.    We deselect the Vietnam records and then select the smaller (by population) Thailand records to see what they are in the map.

 

 

As expected, the smaller records represent the various islands that are part of Thailand in this drawing.     The Thailand area was also decomposed into shape, because part of Thailand fell within the bounding box of the path line that we drew.  

 

We can deselect all the Thailand objects by pressing Edit - Select None, and then we can try Ctrl-clicking various other countries nearby to see which have been decomposed into shapes and which not.

 

 

For example, if we Ctrl-click onto the mainland of Myanmar we see that the mainland portion and all islands immediately are selected in red selection color.   That tells us right away that the multibranched area object for Myanmar has not been decomposed into shapes.

 

If we would like to control which areas are decomposed into shapes, we can do that easily by splitting only selected objects, as shown in the following example.

Example: Split Selected Areas with a Path

We will start from the beginning, and split only selected areas.   We Ctrl-click the areas for Laos and Vietnam to select them.  The original drawing, with which we are working, represents all parts of a country, both mainland and islands, as a single multibranched area object, so a single Ctrl-click on the mainland selects all branches of the object.

 

 

Choosing Draw Path in the cursor mode button, we draw an elaborate path starting to the West of Myanmar, crossing Myanmar, going through Thailand and down into Cambodia, and then up into Thailand and back and forth across Laos and Vietnam before ending in the ocean off the coast of Vietnam.   We right-click to launch the context menu and choose Split.

 

 

In the Split dialog we choose split proportional as the transfer method for the Population_2020 field.

 

 We check the Use selection only box, to apply the split only to selected areas.

 

Press OK.

 

 

The selected areas are split where they were crossed by the path line and have been deselected.

 

 

Looking at the drawing's table, we see that the original two selected objects for Laos and Vietnam have been replaced by the resulting objects, with the populations apportioned between them by the size of each object.

 

In this drawing, Laos had no branches, so it has been split into four areas where it was crossed by the path line.   Vietnam has been split into four main objects where the original mainland shape was crossed by the path line, and in addition it is no longer a branched line but the former shapes that were small branches, islands, are now separate, small, area objects.

 

No other objects in the drawing have been altered, not by being split by the path line and not by being decomposed into constituent shapes.

 

 

For example, if we Ctrl-click the mainland region of Thailand we see that all parts of Thailand are selected in red selection color, showing that Thailand has not been decomposed into constituent shapes.  That is to be expected, because we had checked Use selection only, so only selected objects were altered by the split.  

 

Had we not checked the Use selection only box, then all areas crossed by the path line would have been both split by the line and also those that fell within the bounding box, such as China (an island of which fell within the bounding box) would have been decomposed into constituent shapes.

Example: Split an Area Precisely with a Path

The first example above used a path line drawn free hand to split Vietnam approximately along the 17th parallel.   If we prefer, we can adjust coordinates on the fly in the Coordinates tab of the Info pane to split Vietnam precisely along the 17th parallel.

 

We start again with the original, unmodified drawing, and Ctrl-click the area for Vietnam to select it.

 

 

Choosing Draw Path in the cursor mode button, we draw a path line approximately along the 17th parallel that cuts across Vietnam.  We need not worry about cutting across any other areas since we will check the Use selection only box so only Vietnam will be split.

 

Whenever the Path tool is active, the coordinates for the vertices we click on the path will appear in the Coordinates tab of the Info pane.

 

 

The coordinates appear in the native coordinate system of the active layer, in this case the Latitude / Longitude coordinate system of the Countries drawing.  We double-click into the latitude value boxes and change them to an even 17, to place the two vertices of the path line exactly on the 17th parallel.

 

 

As soon as we change the coordinate values in the Info pane, the vertices defining the path move to the new positions, exactly on the 17th parallel.

 

We right-click to launch the context menu, and then choose Split.

 

 

In the Split dialog we choose split proportional as the transfer method for the Population_2020 field.

 

 We check the Use selection only box, to apply the split only to selected areas.

 

Press OK.

 

 

The result is that Vietnam is split precisely along the 17th parallel.

 

Tech Tip:  When drawing a path, the coordinate numbers for the path vertices appear in the Info pane list in the native coordinate system of the active layer.  In this example, the Countries drawing is in the Latitude / Longitude coordinate system, so the coordinate numbers appeared in decimal latitudes and longitudes.   That made it easy to adjust them to be exactly on the 17th parallel, by entering the number 17 for latitude values.   

 

But suppose the Countries drawing used a different coordinate system, for example, Pseudo-Mercator or some other coordinate system where the numbers that appear in the Coordinates tab might be incomprehensible to us in terms of choosing what the right number is for 17 degrees of latitude?   

 

One simple method is to add a drawing layer that is in Latitude / Longitude, and to make that layer the active layer when drawing a path, so the coordinates of the path appear in decimal latitudes and longitudes.   We can then specify the desired target layer for the split in the Split dialog.  

Example:  Split Areas with an Existing Line

We can use existing lines or areas to split objects, either in the same layer or in a different layer.

 

 

In the map above, we have a Drawing layer that contains a line, as well as the Countries layer showing countries as areas used in prior examples.   We will split the countries of Laos and Vietnam using the line in the Drawing layer.

 

With the focus on the Drawing layer, Alt-click the line to pick it.   We could also Shift-Alt-click the line to pick it and simultaneously make the layer which contains it the active layer.   That is a useful move in maps that have very many layers, or where layers are within groups and it is not immediately clear by which layer an object is hosted.

 

 

Right-click anywhere in the map.  

 

 

Choose Split.

 

 

In the Split dialog, choose Countries as the layer containing areas to be split.   The layer we choose will be remembered in that open window as the default for subsequent Split operations, until we choose a different layer or close the window.

 

 

The Split dialog will populate with fields for the Countries layer.  Choose transfer rules as desired, for example, choosing split proportional as the transfer rule for the Population_2020 field.  

 

At this point we can still Cancel if we want to abandon the split.  

 

Press OK to commit the split.

 

 

Turning off the Drawing layer to hide the cutting line, we can see that the Split command has split Laos and Vietnam exactly along the cutting line.

Example:  Split Areas with an Existing Area

Using an existing area to split objects is similar to using an existing line.

 

 

In the map above, we have a Buffer layer that contains an area, as well as the Countries layer showing countries as areas used in prior examples.   We will split the countries intersected by the area in the Buffer layer.   Note that the area in the Buffer layer has a hole in it.    The Buffer area is shown with partial opacity and a style using an inner border, to more clearly show where the buffer area overlaps various country areas.

 

With the focus on the Buffer layer, Alt-click the area to pick it.   We could also Shift-Alt-click the area to pick it and simultaneously make the layer which contains it the active layer.  

 

 

Right-click anywhere in the map.  

 

 

 

Choose Split.

 

 

In the Split dialog, choose Countries as the layer containing areas to be split.   The layer we choose will be remembered in that open window as the default for subsequent Split operations, until we choose a different layer or close the window.

 

 

The Split dialog will populate with fields for the Countries layer.  Choose transfer rules as desired, for example, choosing split proportional as the transfer rule for the Population_2020 field.  

 

At this point we can still Cancel if we want to abandon the split.  

 

Press OK to commit the split.

 

 

Turning off the Buffer layer to hide the cutting area, we can see that the Split command has split countries intersected by the area exactly along the boundaries of the area.    In the illustration above, we have selected part of Cambodia that has been split by the area.

 

 

We can see that the boundaries of the area were used to split country areas by turning the Buffer layer back on.   In the illustration above, we have selected a part of Cambodia within the hole that was split off by the boundary defining the hole in the area.

 

It does not matter how complex the area is that we use as a cutter:  it can be a very complex area consisting of many islands and holes, and the Split will still be performed exactly along all boundaries in the area.

Example:  Split Areas with a New Line

As an alternative to drawing a path to use as a cutting line, we can begin creating a new line and use the new line in progress as a cutter.

 

 

With the focus on the open map window, choose the Create Line tool in the cursor mode button in the main toolbar.

 

 

Click as desired to mark the line to be created.    When we are happy with the line we have drawn as a cutting line, Right-click to launch the context menu for editing.   Only the line between vertices clicked will be used as a cutter.

 

 

Choose Split.

 

 

In the Split dialog, choose Countries as the layer containing areas to be split.   When we have only one layer in the map, that layer will automatically be chosen.

 

Choose transfer rules as desired, for example, choosing split proportional as the transfer rule for the Population_2020 field.  

 

At this point we can still Cancel if we want to abandon the split.  

 

Press OK to commit the split.

 

 

Areas in the Countries layer are split by the new line that was being drawn.   

 

Since we commanded a Split and never saved changes, no line is drawn.   Instead, the path for the line that was being drawn was used as a cutting line for the split.  The cursor is still in Create Line mode, ready to draw another line if we want to do some more splits.

Example:  Split Areas with a New Area

Creating a new line to use as a cutter is virtually identical to drawing a path to use as a cutter for Split.    We can also create a new area, and use that area in progress as a cutter.   That takes advantage of the "closed" path automatically drawn when creating new areas.

 

 

With the focus on the open map window, choose the Create Area tool in the cursor mode button in the main toolbar.

 

 

Click as desired to mark the area to be created.    When we are happy with the area we have drawn as a cutting area, Right-click to launch the context menu for editing.  Note that as always when creating areas, the point where we last Right-click does not define the area.   The last segment is always a straight line from the first to last vertex clicked for the area.

 

 

Choose Split.

In the Split dialog, choose Countries as the layer containing areas to be split.   When we have only one layer in the map, that layer will automatically be chosen.

 

Choose transfer rules as desired, for example, choosing split proportional as the transfer rule for the Population_2020 field.  

 

At this point we can still Cancel if we want to abandon the split.  

 

Press OK to commit the split.

 

 

Areas in the Countries layer are split by the new line that was being drawn.   

 

Since we commanded a Split and never saved changes, no area is drawn.   Instead, the path for the area that was being drawn (the boundary of the area) was used as a cutting line for the split.  The cursor is still in Create Area mode, ready to draw another area if we want to do some more splits.

Example: Draw a Path using Snap to Split an Area

We can use snapping to precisely mark vertices for the path we use to split an area.

 

 

The illustrations show a blue area adjacent to the Massachusetts coast,  with land areas shown in green.   We want to split the blue area along a line from Cape Ann to Cape Cod.

 

We Ctrl-click the blue area to select it.   Choosing Draw Path in the cursor mode button, we will click to draw the path we will use to cut the blue area.

 

 

We press the spacebar to toggle snapping on, and then, assisted by snapping to snap exactly on the boundary of the area, we click on the boundary of the area at a location on the Cape Ann peninsula.   Next, again assisted by snapping, we click exactly on the tip of Cape Cod.   After that we can press the spacebar to toggle snapping off, and then we right-click anywhere to launch the context menu.

 

In the context menu we choose Split.

 

 

In the Split dialog, choose Land Shapes as the layer containing areas to be split.   When we have only one layer in the map, that layer will automatically be chosen.

 

In the Split dialog check the Use selection only box, to apply the split only to the selected area.

 

Press OK.

 

 

The blue area is immediately split along the path line into two areas, and is deselected.

 

 

We can use style overrides to style one of the new areas a purple color.

 

Example: Draw a Path using Snap to Other Layers

We split an area created in the beginning of the Clip topic, using a path drawn by snapping to an existing line in a different layer.

 

 

The illustrations show a blue area adjacent to the Massachusetts coast,  with land areas shown in green.  Another drawing layer above shows air traffic routes as dashed lines.  We want to split the blue area along the selected lines from Cape Ann to Cape Cod.   We have selected the lines in the illustration above to show where the segments begin and end, to show where we will snap to when drawing the path.

 

We deselect all lines in the ATS_Route layer, and in the Land Shapes layer we Ctrl-click the blue area to select it.  

 

Next, with the focus either on the ATS_Route layer or on the Land Shapes  layer, we choose Draw Path in the cursor mode button.

 

By default, Snap works within the active layer.  If we have the focus on the Land Shapes layer, we should turn off Snap to Active Layer Only.  Before we start clicking to draw the path, we will right-click to set snap parameters.

 

 

We use default settings, except that we uncheck the Snap to Active Layer Only option.  This will allow us to snap to both objects in the ATS_Route layer as well as in the Land Shapes layer.

 

 

We begin drawing the path by clicking at the start of one of the line segments we wish to follow.  

 

 

We click along the segments we wish to follow in drawing the path.  When we are done we right-click to call up the context menu.   

 

In the context menu we choose Split.

 

 

In the Split dialog, choose Land Shapes as the layer containing areas to be split.   

 

 When we have only one layer in the map, that layer will automatically be chosen, but with two layers in the map, if the ATS_Route layer has the focus we want to make sure to choose Land Shapes as the layer with areas to be split.

 

In the Split dialog we check the Use selection only box, and then we press OK.

 

 

The blue area is immediately split into two areas along the path we drew.  Since we created the path by snapping our clicks to air traffic routes, the blue area has been split along a line that follows the air traffic route segments we followed.

 

 

We can use style overrides to style one of the new areas a purple color.

 

The above method is convenient when following along an existing line or area border that does not have too many vertices.   Using snapping we can click on remarkably many vertices with precision, especially considering that even in the middle of drawing a path we can pan and zoom however we like for more precise clicking.     

 

When there are too many vertices to click conveniently using snapping, we can use the Split transform template with the parts option.    The following illustrations show how to use the Split transform template to accomplish the same task as illustrated above.

 

 

We begin by selecting the line segments in the ATS_Route drawing that will be used as cutters.   In the Land Shapes layer we select the blue offshore area that will be split.

 

In the Transform pane, for the Land Shapes layer we choose the Geom field, and then in the list of templates we choose the Split template.

 

 

In the Split template we choose parts as the Split into option, and the ATS_Route layer as the Split with layer.   We check the Split with selection only box, since we only want to use the selected line segments as cutters.

 

The Transform pane does not edit in place when the results of a transform are a greater or lesser number of objects, so the Result is automatically a new table.   We specify a memorable name for the new drawing, Split Shapes, with an analogous name for the drawing's table.

 

Check the Transform selection only box, since we only want to split the selected blue area, and not any of the other areas in that layer.  

 

Press Preview to see what will happen.

 

 

The preview in blue preview color shows how the blue area will be split.  We like what we see, so we press the Transform button to command the transform.

 

A new Split Shapes drawing and table appear in the Project pane.   We can drag and drop it into the map window.

 

 

The result, seen styled using style overrides, is exactly the same as we created interactively using the Clip editing tool.  The difference is that the Clip editing tool altered the Land Shapes drawing to create two new objects that replaced the original blue area that was split. That is convenient when interactively editing a drawing with mouse moves.   The Clip transform template does not modify the Land Shapes layer, but saves the results of the split into a new drawing and table.  That is more efficient when doing mass splits that possibly involve very many complex objects used as cutters to split possibly very many other objects.

Transfer Rules for Split

Transfer rules for Split are similar to those used for joins.

 

 

Transfer rules available depend on the data type of the field, as follows:

 

(none)

Use a NULL value.  Available for any data type.

copy

Use the value in the original object.     Available for any data type.

split

Split the original value equally between resulting objects.  Available for any numeric type binary.

split proportional

Split the original value between resulting objects proportionally to their area (for areas) or length (for lines).   Available for any numeric type.

 

Splitting an original value between resulting objects makes sure that the sum of the resulting values equals the original value, including for integer fields.  For example, splitting 100 into 3 equal parts will produce 33, 33, 34 as values, so the sum of the split results is exactly 100, the original value.

 

Computed fields and unique fields (fields that have a btree index requiring unique values) are carried over from the picked object into all parts, and will be grayed out in the Split dialog, since transfer rules cannot be specified for such fields.  Computed fields will be recomputed.

 

Notes

Permissions - To use Split, the drawing's table must support updating and adding records.  That means, of course, we cannot use Split on drawings stored in read-only data sources or in databases where our user role does not have the ability to update and add records in the drawing's table.

 

Curves and Z removed - Curvilinear segments and Z values are removed from results.

 

Progress and canceling - The Split command shows a progress bar and allows canceling.  That allows using Split with big data sets or with data sets on slow data sources.

 

 

Videos

5 Minute Tutorial - Editing with Clip

 

Newsflash - Merge, Clip, and Split

 

 

See Also

Getting Started

 

User Interface Basics

 

Drawings

 

Snap Modes

 

Clip

 

Erase

 

Merge

 

Measurements

 

Copy and Paste between Drawings or Tables

 

Layers Pane

 

Info Pane

 

Example: Draw Lines, Areas and Points - Simple example of using basic mouse moves to add points, lines and areas to a drawing.

 

Example: Trace an Area in a Map over an Image Background - In a map with a drawing layer above an image layer, create an area object in the drawing by tracing over the outlines of something seen in the image layer below.

 

Example: Edit Coordinates While Creating an Object - When creating an object in a map using a tool such as Create Area, right in the middle of the process we can edit coordinates in the Info pane Coordinates tab.   This example shows the step by step process.

 

Example: Change the Shape of Areas - Step-by-step editing of an existing area in a drawing: changing the shape by moving a vertex, by moving several vertices together, by moving the entire object, by deleting a vertex and by adding a vertex.

 

Example: Add Vertices in the Middle of a Line being Created - During the creation of a new object we can go back and make corrections, additions and deletions to coordinates already marked.  In this example we start creating a new line, and then notice we have skipped over some locations we wanted to click.  We go back to add those vertices (coordinates), and then we continue with creating the line.

 

Videos

Editing Drawings - Create Areas - How to create areas (polygons) in a drawing.  We digitize a lake by tracing over a background satellite image layer from a web server.  This quick video shows how editing tools in Manifold make it easy to digitize objects very quickly, correcting any errors with no stress or fear of getting it wrong.  Includes a quick demo of snapping.

 

Editing Drawings - Create Lines with Curves - A very short video showing how to create lines in drawings using straight segments and also circular arcs.  We create a line in a map of Paris showing our walk around circular ponds. Manifold can create polylines using straight line segments for classic polylines, or using curved segments that are circular arcs, ellipses, or splines for very smooth curves, a much faster and easier technique than clicking many points.  Super!