Buffers

A buffer is a zone at a set distance from a shape's edge. Use it for a safety perimeter around a work site, a no-spray strip around a field, the part of a plot left once a building setback is kept clear, or a corridor along a road, a river or a pipeline. Measure Map draws the zone as a shape of its own, with its own area, and keeps it in step with the shape it was drawn from.

Create a buffer#

1. Click the polygon or line to open its panel.
2. Press Buffer. The Create buffer window opens, with a small map of the shape.
3. Type the Distance, in the distance unit you measure in (metres, feet or yards, for example).
4. For a polygon, choose Where: Outside draws a band around it, Inside a zone set back inside it (see inside a polygon). For a line, choose its Sides and Ends (see along a line).
5. Under Corners, choose how the zone turns the shape's corners (see corners).
6. Check the small map and the area under the settings, then press add_circle_outlineCreate.

The small map shows the zone as you change the settings: filled, with the shape dashed over it. Under the settings, the window gives the Area the buffer will cover. When the distance leaves nothing, such as an inner buffer wider than the polygon, the window says so and add_locationCreate stays off. With the distance empty or at zero, it says Enter a distance greater than zero.

Once the buffer is made, its panel opens.

You need to be able to edit the project: the Buffer button is not shown to people who can only view it.

Corners#

Where the shape has a corner, the zone has to turn it. Corners decides how:

• Sharp: the zone's sides run parallel to the shape's and meet in a point, like a larger copy of the shape, so a field's square corners stay square. The usual choice around plots and buildings, and the one a polygon starts with. Below it, Sharp corner limit sets how far a very sharp corner may reach, in times the distance, before it is cut off: from 1 to 10, and 5 to start with.
• Round: the zone curves around each corner, so every point of its outer edge is exactly the distance from the shape. The usual choice for safety and exclusion zones, and the one a line starts with.
• Cut: the corner is cut off with a straight edge.

What you get#

The buffer is a new shape, named after the original with "(buffer)" after it, such as "North field (buffer)". It has the original's line colour, line style, width, fill, transparency and products, and it is locked. Its label sits on the zone, above the original's, and the lengths of its sides start hidden: turn on Show intermediate distances in its panel to show them.

Around a polygon, the buffer is the band between the original's outline and the zone's outer edge: the original is cut out of it like a hole. Its Area is the area of the band only, and its Perimeter is the length of the outer edge.

The buffer is a shape like any other: open its panel to rename it, change its colours, give it a product or delete it. undo Undo takes it back in one step. You can draw several buffers around the same shape, at different distances.

Inside a polygon#

With Inside, the zone is set back inside the polygon by the distance: the ground left once a strip that wide is kept clear all round, such as the part of a plot a building may stand on. It keeps the same distance from the polygon's holes, so a courtyard grows by the distance too.

An inner buffer is named after the original with "(inner buffer)" after it, such as "Plot 12 (inner buffer)". It is an area of its own: nothing is cut out of the original, and it starts with no products, so the same ground is not priced twice. Give it a product if you want it priced.

Where the polygon narrows to less than twice the distance, the zone comes apart, and each piece becomes a shape of its own, numbered "1", "2" and so on after the name. The window says how many separate areas it will make.

Along a line#

Along a line, the buffer is a corridor, such as a strip either side of a road or a pipe. Sides decides where it lies:

• Both: on both sides of the line.
• Left or Right: on one side only, as a strip along it. Left and right are as the line was drawn, looking from its first point; the small map shows which side that is.

On both sides, Ends shapes the corridor's ends:

• Flat: cut square at the line's first and last points. A line starts with these.
• Round: rounded.
• Square: square, reaching past each end of the line by the buffer distance.

A strip on one side always ends flat.

A buffer drawn along a line is a line itself: the corridor's outline, without a fill, in the line's colour. Its Area is the corridor's.

It follows its shape#

A buffer stays in step with the shape it was drawn from:

• Change the shape's corners, rotate it or edit it in any other way, and the buffer is drawn again from it at the same distance. undo Undo takes back the change and the redrawn buffer together.
• Move the shape, with the Move tool of the magic button or otherwise, and its buffers move with it.

A buffer's panel says what it was drawn from, such as "20 m round South field". Click the shape's name there to open it.

Edit a buffer#

To change its distance, where it goes or its corners, press tuneEdit buffer in the buffer's panel. The same window opens with the buffer's settings: change them and press Save. The buffer is drawn again in place, with its name and colours, in one step you can undo.

What stops it following#

A buffer stops following its shape, and stays as it is, when you:

• unlock it and change its corners by hand;
• move an inner buffer on its own;
• delete one piece of a buffer that came apart, or a ring left inside it.

From then on it is a shape like any other. To have a buffer that follows the shape again, delete it and draw a new one.

You can also detach a buffer on purpose: press link_off Detach buffer in its panel. The pieces drawn with it are detached too. Where the shape was cut out of the buffer, a hole with the shape's outline takes its place, so the buffer keeps its area whatever you later do to the shape. A buffer along a line becomes an area. undo Undo links it again.

If you delete the shape itself, its buffers stay as they were drawn, and their panels say the shape was deleted. Undoing the delete links them again.

A buffer drawn in an older version of the app does not follow its shape: draw it again to make it follow. Nor does one brought in from a file that does not keep buffer settings, such as an older .mmp file or one from another app; a .mmp file saved now keeps them, and its buffers follow their shapes after an import.