Clip

This topic covers the Clip interactive editing command that erases parts of edited areas, lines, or points, using existing areas in a specified layer.

 

 

The Clip command modifies an object being edited (usually an area or a line) by removing those parts of the object that fall inside or outside of existing areas.   The object being edited can be an existing area, line, or point, or it can be a new area, line, or point in the process of being created.  

 

Clip is available in the right-click context menu for editing when creating a new object using Create Area, Create Line, or Create Point, or when an existing object is picked with an alt-click and then put into editing mode with a click on a vertex or segment.   For example, begin drawing a new area, and then right-click and chose Clip to remove portions of that new area which overlap existing areas in the specified layer.

 

Options:

 

 

Clip works by modifying the path that defines the area or line being edited, using existing areas to take a bite out of the path, so that what is left exactly follows the boundaries of the overlapping areas.   

 

Clip is used to clip existing objects, or to create new areas or lines that are automatically clipped to the inside or outside of areas.  Clip can also automatically clip the geometry of paths used for measurement or editing.   Clip can also be used with multipoints, to clip a multipoint to only those "points" within or outside of existing areas, or to create new points ensuring only those new points falling within or outside of existing areas are created.

 

See also the 5 Minute Tutorial - Editing with Clip and Newsflash - Merge, Clip, and Split videos.

Clip vs. Erase

The Clip and Erase commands are similar but opposite:

 

 

With Clip, existing areas are the cutters that modify an object being edited.    With Erase, the area being edited is the cutter that modifies existing objects.

Clip vs. Clip (Transform)

The Clip and Clip (Transform) commands are similar in action, but differ in how many objects are being cut:

 

We use Clip (Transform) when we want to clip many objects throughout a target layer.    We use Clip when we want to interactively delete part of a single object being edited.   Clip (Transform) is great for mass workflow using many areas in one layer to clip many areas, lines, and points in another layer.   Clip is much better when we want to interactively add a single new area that is clipped precisely to the boundaries of existing areas in a layer.

Example

Clip makes it easy to create a new area that is precisely adjacent to Massachusetts coastal areas in the US, shown as green areas in the illustrations below.

 

We start by drawing a new area that overlaps an existing area, clicking a few times to draw the path for the new area.  We only need to be careful outside of the coastline and where the path crosses the coastline,  as everything inside the coastline will be clipped away with great accuracy by the Clip command.

 

 

Right-clicking and choosing Clip by default clips away anything on the inside of the green clipping area, leaving just the outside, which is perfectly aligned to the coastline.  It is as if the green area has taken a bite out of the path for the new object.   If desired, the clipped geometry can be edited further before being applied.

 

 

Applying the edit, we see the newly created area exactly follows the clipped path.  The new area is perfectly adjacent to the green area, with no gaps or overlaps, because it uses exactly the same coordinates as the green area where the Clip command took a bite out of the path for the new object.   

 

Instead of going nuts trying to click many points to follow the coastline, we created the new area by quickly drawing an imprecise path, with plenty of overlap with the green area, and then letting Clip do the hard work of biting precisely into the path and creating dozens of exact coordinates along the border with the green area.  Fast is fun, but fast and easy is even more fun.

 

In the illustration above we have used Style overrides to color the new area differently from the green area.   The new, blue area is in the same layer as the green area.

 

By default, the Clip operation uses all areas in the layer to clip the path.   If the path to be modified overlaps more than one area, then all the areas in the overlap will take a bite out of the path.  For example, suppose we want to add another new area South of Cape Cod, and we want that new area to be perfectly adjacent both to the blue area as well as to the green areas showing mainland and islands.

 

 

We draw the new area, using snapping to click exactly on the corner of the blue area, and being casual about where we click within the overlapping areas.  We then right-click and choose Clip, and all of the overlapping areas will take their bites out of the path.

 

 

The result is a new area that is perfectly adjacent to the blue area as well as to all of the green areas.  Sure beats trying to click all of those points one at a time!

 

 If we want to use only some areas in the layer as clipping areas, we can select those areas, and then tell Clip to use only the selection for clipping.

Summary

Editing with Clip uses the same moves as editing drawings.  Review the Editing Drawings topic for a quick refresher.

 

Create a new area or line with Clip:

 

  1. If only some areas will be used to clip the new object, ctrl-click those areas to select them.

  2. In the cursor mode button in the main toolbar, choose Create Area or Create Line as desired.

  3. Click on desired vertex locations to create the new object in the usual way, overlapping the areas that will be used to clip the new object.

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

  5. In the Clip dialog, choose the layer containing areas that will be used as clipping areas.

  6. Check the Use selection only box to clip only with selected areas.  If that box is not checked, all areas in the layer will be used as clipping areas.

  7. By default, Clip removes everything inside areas used for the clip.  Check the Keep inner part box to keep those parts of the edited object that are inside of clipping areas, and to remove everything outside of areas used for the clip.

  8. Press OK to apply the clip.

  9. If the previewed result looks OK, apply the edit as usual, or abandon the edit if desired.

 

Tech tip:  Remember, we apply edits by pressing Update Record in the Info pane, or by pressing Ctrl-Enter, or by right-clicking anywhere and choosing Save Changes.   We can abandon edits, not making any changes, by right-clicking anywhere and choosing Undo Changes, or by switching to another layer, or by choosing a different cursor mode, or by pressing Ctrl-Backspace.

 

Clip an existing area or line:

 

  1. If only some areas will be used to clip the existing object, ctrl-click those areas to select them.  

  2. Alt-click the area or line to be clipped.

  3. Click on any vertex or segment to put the object into editing mode.  Or, click on the Coordinates tab in the Info pane to enter editing mode.

  4. Right-click anywhere onto the object and choose Clip.

  5. In the Clip dialog, choose the layer containing areas that will be used as clipping areas.

  6. Check the Use selection only box, if desired, to clip only with selected areas.  If that box is not checked, all areas in the layer will be used as clipping areas.

  7. By default, Clip removes everything inside areas used for the clip.  Check the Keep inner part box to keep those parts of the edited object that are inside of clipping areas, and to remove everything outside of areas used for the clip.

  8. Press OK to apply the clip.

  9. If the previewed result looks OK, apply the edit as usual, or abandon the edit if desired.

 

 

Clip a path to measure only inside or outside of areas:

 

  1. If only some areas will be used to clip the measuring path, ctrl-click those areas to select them.  

  2. In the cursor mode button in the main toolbar, choose Draw Path.

  3. Click on desired vertex locations to create the path in the usual way, as shown in the Measurements topic, overlapping the areas that will be used to clip the path.

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

  5. In the Clip dialog, choose the layer containing areas that will be used as clipping areas.

  6. Check the Use selection only box to clip only with selected areas.

  7. By default, Clip removes all parts of the path inside areas used for the clip.  Check the Keep inner part box to keep those parts of the path that are inside of clipping areas, and to remove all parts of the path outside of areas used for the clip.

  8. Press OK.   The measurements reported in the status bar will now be for the remaining segments of the path.

 

 

The choice of layer to be used as the source of clipping areas,  and the checked or unchecked choices in the Use selection only box and the Keep inner part box will persist for that same window until they are changed.  That facilitates repetitive edits using Clip.

Clip an Existing Area or Line

We can modify the geometry of any existing line or area using Clip by first putting the object into coordinates editing mode and then applying Clip to modifying the path that defines that area or line.  If we like the results, we can Save Changes and the object gets clipped.    If we do not like the changes Clip makes, we can Undo Changes and the object will not be clipped.

 

Consider an example using a circular area that was created by using the Buffer transform to create a circular area 200 miles in radius about the Mexican city of Piedras Negras.   The circular area is in a drawing layer called Buffer. The Buffer layer is styled to use yellow color for area fill, and it has an inner border made up of fine hatch lines to better indicate the inside of the buffer area.  A different layer in the same map, called Provinces, shows the provinces of Mexico as area objects.  

 

Our illustration below shows the Buffer layer with 70% opacity in the Layers pane, so we can see where the circular buffer area overlaps areas representing border provinces in Mexico.   We want to clip the circular buffer area so it aligns exactly to the borders of desired provinces, and does not overlap those provinces.

 

 

With the focus on the Mexico layer, we begin by Alt-clicking the circular buffer, to pick it for editing.   By default, that opens the Values tab of the Info pane (not illustrated), to show us any attributes the object may have.

 

 

Click on the Coordinates tab in the Info pane, or click onto any of the segments or vertices of the buffer area to switch the buffer circle into Coordinates editing mode.

 

 

Right-click anywhere in the drawing and choose Clip in the context menu.

 

 

In the Clip dialog, choose Provinces as the layer containing clipping areas.  

 

 

By default, a Clip will use all overlapping areas to bite into the circular area, and it will keep only that part of the circular area that falls outside of any overlapping areas.   If we like, we can check the option boxes to clip only with selected areas, or to keep the part of the circle that falls within any overlapping areas.

 

We go with the default settings, and press OK.  

 

 

The Clip command immediately modifies the path for the buffer circle to clip away all parts of the circular area that fall within any overlapping areas.   The result is that part of the circular object that falls outside of Mexico, with the border of the object precisely adjacent to the province areas along the border.

 

So far, all we have done is use Clip to modify the path that we propose to be the new definition of the circular area that we are editing.   The blue color of the path reminds us that we are simply seeing a preview (blue color is used for previews).    If we do not commit the edit, no changes will be made to the object.   

 

We can commit the edit by pressing Update Record in the Info pane, or by pressing Ctrl-Enter, or by right-clicking anywhere and choosing Save Changes.   We can abandon the edit, not making any changes, by right-clicking anywhere and choosing Undo Changes, or by switching to another layer, or by choosing a different cursor mode, or by pressing Ctrl-Backspace.

 

We press Update Record to commit the edit.

 

 

The circular border is instantly edited into a shape exclusively outside of the Mexican province areas that it overlapped.   It is still picked for editing, in case we want to make further edits to attributes or coordinates.

 

 

We can unpick it by pressing the Esc key, or by changing layers, or by changing the cursor mode, or by Alt-clicking a place in the map with no objects in that layer.   Unpicking the object shows the new shape of the buffer area.

 

 

If we zoom into the map, we can see how the clipped buffer area is precisely adjacent to the various province areas which it formerly overlapped.   There are no gaps or overlaps, because the sequence of coordinates which define the new, clipped boundary of the buffer area use exactly the same coordinates that define the boundaries of the province areas that were used to clip, that is, take a bite out of, the circular buffer area.

Clipping with Selected Areas

By default, Clip will bite into the area or line being edited using all areas in the context layer.   If we prefer, we can use Clip with only selected areas as the clipping areas.

 

Begin by selecting the areas to be used as clipping areas.   In the illustration below, for example, we clicked on the Provinces layer tab to make it the active layer, and then we Ctrl-clicked the area for the province of Nuevo Leon to select that area, causing it to be displayed in red selection color.

 

 

We Shift-Alt-click the circular buffer area to pick it for editing and to simultaneously make the Buffer layer the active layer.   We then click any of the area's vertices or segments to switch into Coordinates editing mode.   

 

 A shortcut to simultaneously pick an object for editing and also to make that object's layer the active layer is to Shift-Alt-click the object.   That is faster than first clicking the Buffer layer's tab to make it the active layer and then Alt-clicking the circular buffer area.   The Shift-Alt-click shortcut is a really super way to make a given object's layer active when we have many layers in a map, or many layers grouped within folders in the Layers pane, and it is not immediately clear what layer the object is in.    Do a quick Shift-Alt-click on the object and that immediately makes the object's layer active.  We can then Alt-click anywhere outside the object, or press Esc, to clear the picked status.   That is faster than browsing the Layers pane to try to figure out what layer the object is in.

 

 

Right-click anywhere, and choose Clip in the context menu.

 

 

In the Clip dialog, choose Provinces as the layer containing clipping areas.  

 

 

For this example, we will check both option boxes:  

 

 

Press OK.

 

 

The preview shows how the path defining the buffer area will be modified.     If we like what we see, we commit the edit, by pressing Update Record in the Info pane, by pressing Ctrl-Enter on the keyboard, or by right-clicking into the map and choosing Save Changes.

 

 

The result is that all parts of the buffer area which did not overlap the selected area are eliminated, leaving only that part of the buffer area that overlapped the selected area.  In the illustration above, the resulting area is still picked for editing, in case we want to change attributes or further edit coordinates.   We can exit editing mode by pressing the Esc key, or by Alt-clicking anywhere in the drawing outside of any objects.

 

We can see what happens when we check Use selection only and we un-check Keep inner part.

 

 

Starting with the original circular buffer area, we Alt-click the area to pick it for editing, we click a vertex or segment to put it into coordinates editing mode, and then we right-click anywhere and choose Clip.

 

In the Clip dialog, choose Provinces as the layer containing clipping areas.  

 

We uncheck the Keep inner part box.   Press OK.

 

 

With the Keep inner part box unchecked, the Clip operation uses the selected area to bite into the circular buffer area, leaving all parts of the buffer area that are outside of the selected area.

 

 

If we commit the edit and then Alt-click outside of any objects to un-pick the result, we can see how the resulting area is precisely aligned to the borders of the selected area.

 

In the example above, we have used only one selected area, but we can use as many selected areas as we like.

 

For example, we can deselect the Nuevo Leon area, and select the areas for Coahuila and Tamaulipas provinces.

 

 

In the Clip dialog, choose Provinces as the layer containing clipping areas.  

 

If we now do a Clip using selected areas, both of the selected areas will take bites out of the circular buffer area.

 

 

The preview shows what the resulting path will look like, a more complex object that follows the borders of the selected areas where the circular buffer area overlaps them.

 

 

Committing the edit, we see the resulting object.   In this particular example the resulting object happens to be contiguous, but it need not be.  

 

For example, suppose that the province of Nuevo Leon did not have an extension to the Northwest reaching the border with the US, but instead the provinces of Coahuila and Tamaulipas joined in that narrow, neck region.  The result of the clip would then be a buffer area with a disconnected island portion within Mexico.    The two parts both would be branches of the same, multibranched area object, but they would appear to be separate objects.

Clip a New Object being Created

The Clip command is a great way to modify new lines and areas as they are being created, so they conform to existing areas.

 

 

We start with a map that has a layer of area objects called OSM areas.  These are areas from the OpenStreetMap data for downtown Boston, seen above with a background Bing streets layer to provide context.   The OSM areas are mostly building footprints, but they also include other areas like parks and various districts.

 

Our map also has a drawing layer called neighborhood, which is currently empty.   Our plan is to draw a new area object that shows a neighborhood of interest.   We would like the object to automatically have holes in it that are exact fits to the various OSM areas that fall within the neighborhood.

 

We will turn off the Bing layer for a less busy display, and we zoom in a bit to the region of interest.

 

 

With the focus on the neighborhood layer, in the cursor mode button on the main toolbar, we choose Create Area and begin clicking to create an area in the usual way.

 

 

When we have drawn the path for our proposed area, we right-click to call up the context menu.   Only the position of clicked vertices matters, so where the cursor is when we right-click does not matter.

 

 

In the context menu, we choose Clip.

 

 

In the Clip dialog, choose OSM areas as the layer containing clipping areas.  

 

 

We would like a default clip, using all areas that fall within or overlap our proposed new area, and creating the new area only in regions outside of those overlapping areas.

 

Press OK.

 

 

Instantly, the Clip command modifies the relatively simple starting path we drew into a far more complex path that includes numerous internal branches that define holes, to cut out places where there are overlapping areas.     

 

So far, all we have is a preview of a proposed new area to create.   If we like, we can abandon the edit, or we can commit the edit to create the new area.

 

 

We commit the edit by pressing Add Record in the Info pane.   We could also press Ctrl-Enter on the keyboard, or right-click and choose Save Changes.   

 

The new area appears in the active neighborhood layer.  We have styled the neighborhood layer to use a light beige color for area fill color, so the new area appears in a contrasting color.

 

 

Turning off the other layers, we can see the really super complexity of the new area that we created with just a few clicks.  

 

 

Turning on the Bing streets background layer, we can see how the new area we created is perfectly georeferenced, as, of course, it should be.

 

If we had checked the Keep inner part box, we would have created a new area that everything clipped away except those parts within overlapping areas.

 

 

The result is seen above.   Although the many parts appear to be separate objects, they are all part of a single, complex, multibranched area object.

 

 

We can see that by Ctrl-clicking any of the parts.  They all will be selected, since they are all part of the same area, a single record in the associated table.

Using Clip to Fill Open Regions

The Clip command is arranged so that a single, simple command can accomplish many different tasks for which older GIS packages may use separate commands.   For example, some GIS packages provide a "Fill" or "Trace" command that can be used to create area objects that fill in portions of a drawing between other areas, such as filling in open holes for lakes.

 

We can do that easily with Clip.

 

 

Consider the map above, which has one layer that shows land areas in North America, called Land Shapes, using green color for areas.   The Great Lakes appear as holes in the big area that forms North America.   We have added a drawing layer, called Great Lakes, that is currently empty.

 

In the illustration above, in the Layers pane we have set transparent color for the background, to make it clear there are no objects located within the holes formed by the shorelines of the big North America land shapes area. 

 

 

With the focus on the Great Lakes layer, in the cursor mode button on the main toolbar, we choose Create Area and begin clicking to create an area in the usual way.   We can draw a large area casually and imprecisely, so long as it entirely encloses the empty spaces where we would like to create the new area.

 

When we have drawn the path for our proposed area, we right-click to call up the context menu.   Only the position of clicked vertices matters, so where the cursor is when we right-click does not matter.

 

 

In the context menu, we choose Clip.

 

 

In the Clip dialog, choose Land Shapes as the layer containing clipping areas.  

 

 

Verify both option boxes are not checked.   Press OK.

 

 

The Clip command immediately modifies the simple path we drew into a highly complex path, containing multiple branches, that precisely follows the coastlines of the land area.

 

We commit the edit by pressing Add Record in the Info pane.   We could also press Ctrl-Enter on the keyboard, or right-click and choose Save Changes.

 

 

The new area appears, precisely filling in the open spaces within the region where we drew our new area.   

 

The result is seen above, with the Great Lakes layer styled in a different color for areas, with an inner border effect to add visual interest.     In this view, we can see that the new area we created to fill in the Great Lakes spaces in the Land Shape area is a complex, multibranched area, with non-contiguous parts such as those for Lake Erie and Lake Ontario, and also containing many holes for the land area islands in Lake Superior, Lake Michigan and the other lakes.  

 

 

Zooming in, we see the perfect adjacency of the new area, as it precisely abuts the land areas that were used to clip the path that created the area.

Clipping Existing Lines

Clip also works with lines.    We demonstrate by clipping a line used to show dimensions.  

 

We start with a map of a house that in the Layers pane has many layers grouped into two folders, one folder for the first floor and one folder for the second floor.  

 

One of the layers in the first floor group is a vector drawing layer that shows dimension lines.   The lines are styled with arrow heads at the beginning and the end, to use as dimensioning lines.  An additional layer above the dimension lines provides labels, which take the length of the line from a computed field giving the length of the dimensioning line.  The house is in Europe, so the metric system is used and the units of measure in the coordinate system are meters.   We are adding dimension lines to the kitchen, measuring the width of work areas on the kitchen counters and between counters.  

 

 

Another of the layers in the first floor group  is a layer called 1st Kitchen Counters, in which the kitchen counters are shown using area objects.   We would like to clip the measuring line seen above so it measures the distance between counters within the work area by the stove top and sink.   We will clip the dimension line by using the width of the counters in the 1st Kitchen Counters layer.

 

We begin by Shift-Alt-clicking the line to pick it, which also automatically makes the active layer the layer containing the line, taking care to click a spot that is not over a counter so we do not accidentally pick the counter layer.   Using Shift-Alt-click to simultaneously pick an object and to also switch the active layer to the layer that contains the picked object is a faster technique when working with many layers in groups than first switching to the dimensioning lines layer as the active layer and then Alt-clicking the line.  

 

We then click the body of the line or a vertex at either end to put the line into editing mode.

 

 

The line appears in editing mode, with vertices shown as larger blue boxes, with the active vertex the largest blue box.   The Info pane (not seen in the illustration) shows the coordinates of the line when it is in editing mode.   The active layer in the group has switched to 1st Dimension Lines, since that is the layer that hosts the line which we Shift-Alt-clicked.

 

We right-click anywhere in the map window to launch the context menu, and in the menu we choose Clip.

 

 

In the Clip dialog, choose 1st Kitchen Counters as the layer containing clipping areas.  

 

The Clip dialog shows default settings.   We do not need to select anything because the line only crosses one area, so the default use of all areas for clipping works for us.   

 

Press OK.    

 

 

The path for the line is clipped to only those parts of the line outside of any areas that the line crosses.    

 

At this point, we can abandon edits by right-clicking and choosing Undo Changes.     

 

To save the changes, we right-click and choose Save Changes.   We can also press Update Record in the Info pane to save the changes.

 

 

Alt-click anywhere in the map to unpick the line.   The result is a line that has been clipped to outside of any overlapping areas.  It now reports the horizontal distance in the work zone within the U-shaped kitchen counter.  1.7 meters is about five and a half feet, a comfortable space for one person, and enough for two people to work the kitchen at the same time.   

Keeping the Inner Part

If we wanted to clip the line so it measured the width of the counter in the rounded peninsula, that is easy to do.

 

 

Beginning with the original line, we Alt-click the line to pick it, and then we click it again to begin editing the line.  Right-click anywhere in the map window and choose Clip from the editing context menu.  

 

In the Clip dialog, choose 1st Kitchen Counters as the layer containing clipping areas.  

 

In the Clip dialog, check the Keep inner part option.   Press OK, and then press Update Record in the Info pane to save the changes.   We could also right-click and choose Save Changes.  to save the changes.  

 

 

The result is a dimensioning line giving the width of the peninsular part of the counter.  

Clipping Existing Lines

We demonstrate a more complex clip of a complex line by clipping a graticule so it only appears over land.

 

 

In the illustration above, we have added a Graticule drawing layer, that provides latitude and longitude lines spaced five degrees apart, above a Land Shapes layer that shows land areas surrounding the Great Lakes.   To create the graticule, we downloaded a set of vie degree graticule lines from the Natural Earth web site.   We deleted all lines except those in our region of interest, and then we merged them together into a single line object.

 

 This example is a bit contrived.   The Clip interactive editing command works with one object that has been picked, an area or a line.   To clip an entire graticule's worth of lines with the Clip editing command, we must merge them into a single, multibranched line, and then we can clip that single line object.   A more sensible way to do the same thing would be to use the Clip transform template.   That would enable us to instantly clip hundreds of different graticule lines with the land areas, keeping the inner part or the outer part.    Very often the choice whether we use the Clip editing command or the Clip transform template is the number of objects we are using.  If it is just a few local lines that will be subject to interactive editing, it can be more convenient to merge them together and then use Clip editing.  If it is many lines all over the world we would prefer to use the Clip transform template.

 

Proceeding with this example, we Alt-click the graticule, doing so in a region where there is not also a land area in the same place, so we can be sure to pick only the graticule and not the land area.

 

 

That picks the graticule for editing.  Since it is all one line object, the entire graticule appears with coordinate handles.   Natural Earth provides graticule lines made up of many intermediate segments, so when they are projected the result is still pleasing.   

 

Click any of the vertices or segments to switch into coordinate editing mode.

 

 

Right-click anywhere to launch the coordinate editing context menu.

 

 

Choose Clip.

 

 

In the Clip dialog, choose Land Shapes as the layer containing clipping areas.  

 

 

In the Clip menu, check the Keep inner part box, and press OK.

 

 

Immediately, the path making up the graticule is edited to segments that only fall within the land areas, and not over the empty places where the Great Lakes are located.

 

So far in our workflow, the editing of the graticule object is still provisional.   We can abandon edits if we like by right-clicking anywhere in the map and choosing Undo Changes, or by clicking on a different layer.  

 

We can commit the edit by pressing the Update Record button in the Info pane, or by right-clicking anywhere in the map and choosing Save Changes.    

 

We right-click in the map and choose Save Changes.  We then Alt-click anywhere away from the graticule line to unpick it.

 

 

We add the Great Lakes layer created earlier to see the new graticule that now exists only over land areas.

Clip a Measurement Path, or a New Line

In Manifold we measure distances and bearings by drawing a path, as illustrated in the Measurements topic.  When we want to measure over a path that includes only those portions inside or outside of given areas, the Clip command is an easy way to do so.   We start with a simple path that is easy to draw, and then we let Clip edit that path into to what might be many, intricate segments.  

 

Drawing paths is the same as creating a new line, so the same procedure below also works for using Clip to modify a new line created using the Create Line tool.

 

 

With the focus on the Land Shapes layer, in the cursor mode button we choose Draw Path, and then, as shown in the Measurements topic, we click twice to draw a path across the Great Lakes region.

 

Right-click to launch the context menu.

 

 

Choose Clip.

 

 

With only one layer in the map, the Land Shapes layer is automatically chosen in the Clip dialog as the source of clipping areas.  If there were other layers in the map, in the Clip dialog we would choose Land Shapes as the layer containing clipping areas.  

 

Verify both option boxes are not checked.   Press OK.

 

 

Clip uses the land areas to take a bite out of the path, leaving only those portions of the path that are outside of the clipping land areas.   

 

 

Looking at the measurement readout in the status bar, we see the total length over water is about 645 kilometers.  

 

 

If we would like to copy the length to the Windows Clipboard, we can do that by right-clicking anywhere in the map and choosing Copy Length.   See the discussion in the Measurements topic.

Measuring Distances within Walls

Clip is a very handy way to modify paths to enable fast measurements that otherwise are difficult to do.   

 

Consider the example below, which shows a simplified layout of a house in France built with classic European construction methods, with thick masonry exterior walls and masonry interior walls built of expanded concrete blocks or hollow clay bricks faced with plaster finish.   Such construction can last for centuries and provides excellent fire resistance, but can impede line of sight WiFi radio transmissions used by modern gadgets.    

 

The map below was drawn with accurate locations and measurements, and is located at the 0,0 origin of a Mercator projection that uses a spherical Earth ellipsoid, so it provides a reasonable GIS setting for CAD style work and accurate measurements, without non-spherical Earth ellipsoid distortions.

 

 

Our task is to place several WiFi linked security cameras we will use to keep an eye on our European villa when travelling abroad.  The proposed location of the WiFi access point is marked in a utility room.  Various locations for cameras are indicated with camera point icons.  We want to check how much masonry  the signal must pass through to the various camera locations, so we can interactively try out different camera locations to provide a good view into areas of interest where the path to the access point passes through the minimum amount of masonry.

 

We will work with the focus on the Inner Walls layer, since those indicate the masonry walls through which the signal must pass.   We will turn Snap to Active Layer off, in the Snap modes, so that even though we will have the focus on the Inner Walls  layer, we can snap to access point and camera points that are all in the WiFi Gadgets layer.

 

 

With the focus on the Inner Walls layer, in the cursor mode button choose the Draw Paths tool.   Press the spacebar to toggle snapping on (or right click and choose Snap) with the default Snap to Coordinates mode, so the cursor can snap to WiFi gadget points.  

 

Click on the WiFi access point, and then click on the camera shown above.

 

 

The status bar readout shows the straight line distance between the two is about 9.5 meters, about 31 feet.   

 

To find the distance within masonry walls, we right-click anywhere in the map to launch the context menu.

 

 

Choose Clip.  

 

 

Since we had the focus on the Inner Walls layer as the active layer when we started drawing the path, that layer is automatically chosen in the Clip dialog as the source of clipping areas.  If we had the focus on another layer, in the Clip dialog we would choose Inner Walls as the layer containing clipping areas.  

 

Check the Keep inner part box and press OK.

 

 

Instantly, the Clip tool edits the path to consist only of segments that fall within the masonry walls.   

 

 

The status bar readout tells us the straight line distance within masonry is about four and a quarter meters, or almost 14 feet.   Depending on the masonry, that might be a problem.   If we positioned that same camera a bit lower in the diagram, we could reduce the path through masonry to almost nothing, by avoiding a diagonal path the long way through a wall.

 

To record the distance, we can right-click and choose Copy Length to copy the length through walls to the Windows Clipboard, so we can then paste the length where desired.

 

We can quickly click twice to draw a straight line path from the WiFi access point to any camera location, and then do a quick clip to see what the distance through walls will be.

 

 

For example, looking at the distance through walls to the camera indicated above, we see that although the camera is farther away, the straight line distance through walls is only about 2.5 meters.

 

Notes

WiFi distances - WiFi signal propagation is more complicated than simple straight line distance, but the method above is still helpful in many settings to get an idea of possible problems with signal strength.

 

Permissions - To use Clip, the drawing's table must support updating and adding records.  That means, of course, we cannot use Clip 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 Clip command shows a progress bar and allows canceling.  That allows using Clip with big data sets or with data sets on slow data sources.

 

Dimension lines - The dimension lines shown in one of the examples in this topic were labeled by their length.  the computed field used to given the length of the line (for use in labels) to simply

 

GeomLength([Geom], 0)

 

Videos

5 Minute Tutorial - Editing with Clip

 

Newsflash - Merge, Clip, and Split

 

See Also

Getting Started

 

User Interface Basics

 

Drawings

 

Snap Modes

 

Erase

 

Merge

 

Split

 

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!