Map Editor Tool

Overview

The Map Editor Tool is a comprehensive spatial editing system that provides professional-grade geometric creation, modification, and spatial analysis capabilities. This sophisticated tool integrates ArcGIS drawing tools with advanced spatial operations, offering multiple geometry types, intelligent snapping systems, complex spatial analysis functions, and export capabilities optimized for professional GIS workflows and spatial data management applications.

A typical session follows four steps:

1. Create features — draw, select, or add them by coordinates, using the drawing options to control how they are drawn.
2. Combine and split them against a second set of shapes, or reshape them with the shape tools.
3. Step back with Undo, Redo and Reset whenever something goes wrong.
4. Export or save the result as a file or a personal MyLayer.

Opening the Editor

1. Locate Map Editor Icon
2. Click to open editor panel

The Target and Ref dropdowns list only the layers that are visible on the map at that moment (feature layers and queryable map services). When the panel opens, the first of them is picked for both (unless a layer you chose earlier is still visible); if no such layer is visible, a No Feature layers found warning appears and the dropdowns stay empty. Switch a layer on in the layer list, then click the dropdown — it refreshes its list each time you click it.

Most of the panel waits for a Target layer: the Target and Ref buttons, the Buffer input, Coordinate Input, the Combine & Split and Shape Tools groups, and the Export buttons are hidden until a Target layer is chosen.

Panel Layout

The panel reads top to bottom in the order you work:

Area	What it holds
Drawing options row	The Multi, Snap and Meas switches and the Line style picker
Snapping Layers	The list of layers to snap to — shown while snapping is on
Coordinate Input	Collapsible section for adding a point by coordinates — shown once a Target layer is chosen
Target row	Target layer dropdown, Select, the Polygon / Line / Point draw buttons, Edit and Buffer
Ref (reference) row	Ref layer dropdown, the same Select / draw / Buffer buttons, and the shared Buffer distance input
Undo / Redo / Reset row	Panel-level history controls
Operation groups	Three collapsible groups: Combine & Split, Shape Tools — Target only, and Export / Save, the last step

Target and Reference Layers

The editor works with two graphics layers. The target layer holds the shapes you are building; the Ref (reference) layer holds a second set of shapes used as input to the Combine & Split operations. The shape tools and both export paths use the target layer only.

Operation Groups

The operation buttons are organised into three collapsible groups, so it is clear what each one needs as input:

Group	Needs	Contains
Combine & Split	Target and Reference shapes	Intersect, Cut Shape, Merge Shape, Split Shape, XOR, Reshape
Shape Tools — Target only	Target shapes only	Offset, Simplify, Explode, Hull, To Lines, To Polygons
Export / Save	Finished shapes	Shapefile, GeoPackage, GeoJSON, KML, FIRS, Save MyLayer

Export / Save is the last step of the workflow, so it starts collapsed. Hover any button in a group to see its tooltip.

Creating Features

Drawing Tools

Available geometry types:

• Polygon:
• Line:
• Point:

Drawing steps:

1. Select geometry type
2. Click map to draw
3. Double-click to complete

Selecting Existing Features

1. Choose layer from dropdown
2. Click 'Select' button
3. Click layer on map
4. Click 'Select' again to deactivate

Adding a Point from Coordinates

Instead of clicking the map, you can place a point at an exact location. The Coordinate Input section sits below the drawing options once a Target layer is chosen, and starts collapsed:

1. Open Coordinate Input
2. Enter X / Easting and Y / Northing (MGA Zone 55, EPSG:28355)
3. Click Add Point from Coordinates — the point is added to the target layer and the map zooms to it

The usual Tasmanian range is Easting 190,000–640,000 and Northing 5,120,000–5,630,000. A point outside that range is still added, but a Coordinates Outside Typical Bounds notice warns you, so check for swapped or mistyped values.

Buffering a Shape

Both the target and the reference row have a Buffer button, and they share the Buffer distance input:

1. Enter buffer distance
2. Click buffer button

One Geometry Type at a Time

The editor holds one geometry type at a time, because both export and Save to MyLayer handle a single type. If you already have shapes of one type and start adding another — with Multi on, arming a different draw tool or selecting a feature of another type; in either mode, adding a point by coordinates — a Remove Existing Shapes? dialog appears first. (With Multi off, the editor keeps only your latest shape anyway, so a new draw or selection simply replaces it.)

• Remove and Continue — clears the existing shapes and proceeds. The clear is recorded, so Undo brings them back.
• Cancel — nothing is removed and whatever you had armed or selected stays as it was.

Switching the Target or Ref dropdown to a layer of a different geometry type asks first too, in a Different Geometry Type dialog: Switch Anyway removes the shapes and switches; Cancel keeps the shapes and the previous layer. Switching to a layer of the same geometry type keeps your shapes.

Drawing Options

Above the drawing buttons is a row of drawing options: three switches — Multi, Snap and Meas — and the Line style picker. The switch labels are abbreviated so all four controls fit on one line in a narrow panel; hover any of them to see a tooltip with the full meaning. On a narrow panel or a small screen the row wraps onto a second line rather than hiding anything.

Multi — Continuous Drawing

Enable continuous drawing by toggling the Multi switch (tooltip: Keep drawing — the tool stays armed after each shape). When active, every feature you complete (point, line, or polygon) is kept and the same drawing tool re-arms, so you can draw the next feature immediately without re-clicking the draw button. Selected features accumulate in the same way.

With Multi off, the editor keeps only your latest shape on that layer — each new shape you draw or select replaces the previous one.

Snap — Snapping to Features

Snapping lets the vertices you draw lock onto features of other layers. Turn the Snap switch on: this fills the Snapping Layers list below the row (click its heading to expand it). Tick the layers you want to snap to — the chip shows how many are ticked. Snapping applies only while at least one layer is ticked.

• Only feature layers can be snapped to, so only they are listed. Most catalogue layers — Roads among them — are drawn as map images, and they do not appear in the list.
• When the panel opens, the Snapping Layers section can already show below the row while the Snap switch still looks off, and its list can read No layers available for snapping. Turn the Snap switch on to fill it.
• Reset switches snapping off and clears the ticks.

Meas — Real-Time Measurement Display

Toggle the Meas switch to display live measurements while drawing:

• Polygons: Shows area in hectares (ha) at the polygon centroid
• Polylines: Shows length in metres (m), automatically converting to kilometres (km) at 1,000 m or above
• Measurements update in real-time as you add vertices or edit shapes
• A final measurement label persists on the completed feature
• Calculations use geodetic (curved-earth) measurement for accuracy

INFO

Measurement operators are lazy-loaded when you first enable the Measure toggle, so there may be a brief delay on first activation.

Line Style — Straight or Arc

The Line style picker at the end of the drawing options row controls how the line tool reads your clicks. It has two icon buttons:

Style	Icon	How your clicks are read
Straight (default)	straight line	Every click is a vertex, joined by straight segments — the long-standing behaviour.
Arc	curved segment	Clicks are read as a chain of curves: the first click starts the line, then each pair of clicks is a point to curve through followed by the end point of that curve.

While Arc is selected, a reminder line appears under the row:

Arc: click a start point, then a point to curve through and an end point — repeat the last two for each further curve.

Drawing an arc:

1. Set the line style to Arc
2. Click the line tool
3. Click the start point
4. Click a point the curve should pass through, then click the curve's end point
5. Repeat step 4 for each further curve — each new curve continues from the previous end point
6. Double-click to complete the line

The curve appears live as you click, so you can see the shape before finishing. Three clicks give one curve, five clicks give two joined curves, and so on.

Arc lines behave like any other line

A finished arc is stored as a closely-followed series of vertices (accurate to within about 0.25 m of the true curve), so everything else works normally — measurement, the shape tools, spatial operations, Reset, export to Shapefile/GeoPackage/GeoJSON/KML/FIRS, and Save to MyLayer. Nothing downstream has to be done differently.

Notes

• The line style applies to lines only — points and polygons are unaffected.
• It governs both the target and the reference line tools, and works with Multi, Snap and Meas.
• Your choice stays selected between draws, so you can draw several arc lines in a row. It also stays selected if you close and reopen the editor — it returns to Straight only when you reload Horizon. If a line comes out curved when you expected it straight, check this picker first.

When a curve stays straight

A curve needs a genuine bend. If the middle (through) click sits almost on the straight line between the start and end points, or beyond the end point, that piece is drawn as straight segments instead — this prevents an accidental click from producing a huge unintended sweep. Place the middle click clearly to one side, and between the start and end points.

If you finish with an odd number of clicks left over, the last unpaired click is joined as a straight segment.

Combine & Split

The Combine & Split group holds the six operations that use the shapes on the target layer together with the shapes on the reference layer. The buttons show icons only, so hover one to see its name.

If you learned the older button names

Three of these buttons were renamed to say plainly what they do. The operations themselves are unchanged — the same button does the same thing, only the wording on the tooltip is different.

You used to hover	It now reads	What it does
Subtract	Cut Shape	Removes the reference shapes from the target shapes
Union	Merge Shape	Combines the shapes into one
Cut	Split Shape	Splits a target polygon along a reference line

Take particular care with Cut: it used to mean "split a polygon with a line", and that is now Split Shape. Cut Shape is the old Subtract. Two of the button icons changed at the same time, so the row may not look quite the way you remember it either.

Available Operations

Each button is named below exactly as its tooltip reads:

Button	What it does
Intersect Shape	Keeps only the area covered by both the target and the reference shapes.
Cut Shape	Removes the reference shapes from the target shapes (the difference between them).
Merge Shape	Combines the target shapes into one. Reference shapes are merged in as well when the reference layer holds any; any that are not the same geometry type as the target are left out, and a note tells you how many.
Split Shape	Splits the target polygons along a reference line.
XOR Shape (symmetric difference)	Keeps the parts covered by the target or the reference shapes, but not both. Target and reference must be the same geometry type.
Reshape Shape (draw a Ref line across it)	Redraws part of a target polygon or line to follow a line you draw in the reference layer.

• Intersect

• Cut Shape

• Merge Shape

• Split Shape

• XOR

• Reshape

Using Split Shape

1. Draw or select the polygon(s) you want to divide in the target layer
2. Draw or select a line in the reference layer that crosses them
3. Click Split Shape

Split needs at least one polygon on the target layer and at least one line on the reference layer; if either is missing, the tool says so rather than doing nothing.

Using Reshape

1. Draw or select the polygon(s) or line(s) you want to change in the target layer
2. Draw one continuous line in the reference layer that crosses the target shape
3. Click Reshape

The target shape's boundary is re-routed to follow the reference line, and the reference layer is cleared.

WARNING

Reshape needs exactly one reference line with a single unbroken path. If the reference layer holds more than one line — or a line drawn in separate pieces — the tool reports that it needs a single continuous line. If the line does not actually cross a target shape, nothing is reshaped.

Using XOR

1. Draw or select the target shape(s)
2. Draw or select the reference shape(s) — they must be the same geometry type as the target
3. Click XOR

The result is everything covered by one set or the other, with the shared overlap removed. If the two sets cover exactly the same area, nothing remains and the tool reports this instead of clearing your work.

Shape Tools

The Shape Tools — Target only group holds the tools that reshape, tidy up, or restructure the geometry already on the target layer — no reference layer is involved. Every tool replaces the target shapes with its result — the same read-and-replace behaviour as Merge Shape and Buffer — so you can chain tools one after another, step back with Undo, or use Reset to start again.

Hover any button to see its tooltip.

Tool	What it does
Offset	Shifts target lines and polygons sideways by the signed Distance value, using the selected corner style.
Simplify	Removes surplus vertices from target polygons/lines, using the Distance value as the maximum allowed deviation.
Explode	Splits multipart shapes into one separate shape per part.
Hull	Replaces all target shapes with the single convex hull (the tightest enclosing boundary) around them.
To Lines	Converts target polygons into boundary lines — each ring becomes a line. See conversion notes.
To Polygons	Converts target lines into polygons, filling the areas they enclose. See conversion notes.

Explode

TIP

XOR and Reshape are shape-changing tools too, but they live in the Combine & Split group because they also need the reference layer.

The Distance Input

Simplify and Offset both read the shared Distance field (in metres, 10 when the panel opens) that sits on the same line as the Offset button:

• Simplify uses the absolute value as the maximum deviation — a larger number removes more vertices.
• Offset uses the signed value:
  • Line — a positive distance offsets to the right of the line's drawn direction, a negative distance to the left.
  • Polygon — a positive distance expands the polygon outwards, a negative distance contracts it inwards.

Offset is not the same as Buffer

Buffer always grows a shape outwards in every direction and turns a line into a polygon. Offset shifts a shape sideways and keeps a line as a line, so it is the tool to use for parallel tracks, road setbacks, or shrinking a polygon slightly.

Offset Corner Style

Offset is a split button: the left half runs the offset, and the arrow on the right picks how corners are treated. The active choice is shown underneath as Corner style: …, and it stays selected between offsets.

Corner style	Result
Miter (default)	Sharp corners, extended to a point. Very acute corners are trimmed automatically instead of spiking.
Round	Corners are rounded off with a smooth arc.
Bevel	Corners are cut off with a straight edge.
Square	Corners are squared off.

If an offset is refused

Offsetting a polygon inwards repeatedly eventually collapses it on itself. When that happens — or when a result would become excessively complex — the shape is left as it was and the message reports how many shapes could not be offset, so a further click cannot progressively mangle your geometry.

Converting Between Lines and Polygons

• To Lines needs at least one polygon on the target layer. Each polygon's rings become boundary lines, and the polygons are replaced by them.
• To Polygons needs lines on the target layer and works on all of them at once, filling every enclosed area. A hand-drawn loop rarely ends exactly on its start point, so a nearly-closed line is closed for you before the conversion; a clearly open line (a V, an out-and-back) is left alone rather than having area invented for it. If nothing is enclosed, the tool says so and your lines are kept.

Notification Messages

Each shape tool reports what it did, for example:

• "Reshaped 2 shapes"
• "Exploded 1 multipart shape into 4 shapes"
• "Simplified: 412 vertices down to 96"
• "Offset 3 shapes successfully"
• "Converted 2 polygons to boundary lines"

If a tool cannot run, the message explains why — for example "Enter a non-zero distance in meters", "Offset works on lines and polygons — draw or select one in the target layer", or "No multipart shapes to explode".

Undo, Redo and Reset

The row above the operation groups holds Undo, Redo and Reset. They act on the editor as a whole and stay available even if the selected target layer disappears from the map.

• Undo steps back through your operations — draws, selections, buffers, spatial operations, shape tools, and the clear that happens when you switch layers or press Reset. Up to 20 steps are kept.
• Redo steps forward again. Undo and Redo are greyed out when there is nothing to step through.
• Reset clears both the target and reference layers — and is itself undoable, so an accidental Reset can be recovered with Undo. It also switches Multi and Snap off and clears the snapping layer ticks.

"Nothing to Redo"

If you undo something and then make a new change, the redo history no longer applies and a short Nothing to Redo notice explains why the button stopped working. Redoing after finishing a shape edit does the same — the completed edit starts a new step.

Export and Save

The Export / Save group at the bottom of the panel starts collapsed — click its heading to open it. Inside are two tabs — Export and Save MyLayer. The Export tab is selected by default, and switching between the two tabs does not lose what you have typed in the other. The Export and FIRS buttons appear once a Target layer is chosen, and stay disabled until there are shapes on the target layer.

Format Options

Click Export and pick a format from the menu:

• Shapefile — Exports drawn geometry as a Shapefile in the map's native projection (GDA94 / MGA Zone 55).
• GeoPackage — Exports as a single .gpkg file, also in the map's native projection. Keeps full attribute types and long field names, neither of which survives a Shapefile's DBF format.

• GeoJSON — Exports as a single .geojson text file, the format most web maps and code libraries read directly. Reprojected to WGS 84.
• KML — Exports drawn geometry in KML format. Reprojected to WGS 84.

• FIRS — Exports drawn geometry as a Shapefile reprojected to WGS 84 (EPSG:4326) coordinates, formatted for import into the Fire Incident Reporting System (FIRS). Use this option when you need to submit spatial data to FIRS.

Exporting a File

1. Optional: Enter filename

2. Click Export and choose Shapefile, GeoPackage, GeoJSON, or KML — or click FIRS for the FIRS system

Saving to a MyLayer

Instead of downloading a file, you can keep the geometry in Horizon as a personal layer:

1. Open Export / Save and switch to the Save MyLayer tab
2. Enter a MyLayer Name — this identifies the layer and must be unique among your own layers
3. Enter a Display Label — the name shown on the map and in the layer list
4. Click Save

The saved layer then appears in the My Layers Tool, where you can show, style, or export it later.

INFO

If the MyLayer name is already in use, the Name Already Exists dialog asks whether to replace the existing layer.

Overlapping Geometry Detection

Before your shapes are written to a file or saved to a MyLayer, the editor checks whether any of them overlap each other at the same location — for example the same polygon drawn twice, or two lines sharing a segment. This catches the common mistake of exporting duplicated or stacked geometry without noticing.

If an overlap is found, an Overlapping Geometry Detected dialog appears and pauses the export/save until you choose how to proceed.

What counts as an overlap:

• Polygons whose intersection has real area (edge-touching polygons are not flagged).
• Lines that share a segment (lines that merely cross at a single point are not flagged).
• Points that sit at the same location (coincident duplicates).

Only like-with-like shapes are compared, so a point is never treated as overlapping a polygon or a line.

Dialog choices:

• Merge — combines each overlapping group into a single feature. Non-overlapping shapes are left unchanged.
• Keep Separate — proceeds with every shape exactly as drawn, overlaps included.
• Cancel — stops the export/save so you can go back and edit the shapes.

INFO

The overlap check applies to all export formats (Shapefile, GeoPackage, GeoJSON, KML, FIRS) and to Save to MyLayer. If no overlaps are detected, the dialog does not appear and the export/save continues as normal.

Name Already Exists Dialog

When saving geometry to a MyLayer name that already exists, a warning dialog appears to prevent accidental overwrites.

Dialog Details:

• Heading: "Name Already Exists"
• Kind: Warning (yellow indicator)
• Modal: Yes — you must respond before continuing
• Content: Displays the existing layer name and geometry type, and asks whether to replace the existing layer with the new geometry
• Footer Buttons:
  • Cancel (left) — closes the dialog without changes
  • Replace (right) — overwrites the existing MyLayer with the new geometry

The dialog prevents closing via the Escape key or clicking outside, ensuring you make an explicit choice.

Exporting a Saved MyLayer

To export previously saved MyLayers to Shapefile or KML format, use the export options in the My Layers Tool. Each saved layer has an export dropdown with Export as SHP and Export as KML options.

Troubleshooting

Drawing and Selecting

Issue	Solution
Layer selection fails	Check layer visibility
Operation errors	Verify geometry validity
Target and Ref dropdowns are empty, and no buttons show	The dropdowns list only visible layers — switch a layer on, then click the dropdown to refresh it
A Roads (or other catalogue) layer is missing from Snapping Layers	Only feature layers can be snapped to; layers drawn as map images are not listed
"Coordinates Outside Typical Bounds" when adding a point	The point was still added — X/Y are MGA Zone 55 metres, normally Easting 190,000–640,000 and Northing 5,120,000–5,630,000; check for swapped or mistyped values, then Undo if needed
"Remove Existing Shapes?" keeps appearing	The editor holds one geometry type at a time; finish and export/save the current shapes, or choose Remove and Continue
Drawing options row is on two lines	Expected on a narrow panel or small screen — widen the browser window, or the panel, to fit Multi / Snap / Meas and Line style on one line
Arc line style draws straight segments	The middle (through) click was almost on the line between the start and end points, or past the end point — click it clearly to one side and between them
Only part of my arc line is curved	Each curve needs two clicks after the start (through, then end); a leftover unpaired click is joined as a straight segment
Line style picker has no effect	It applies to the line tool only — points and polygons always draw as before

Combine & Split

Issue	Solution
I cannot find Subtract or Union	They were renamed — Subtract is now Cut Shape and Union is now Merge Shape. Nothing about what they do has changed
Cut Shape did not split my polygon along a line	Cut Shape removes the reference shapes from the target. To divide a polygon with a line, use Split Shape
Cut Shape says nothing remains after the cut	The reference shapes cover the whole target, so there is nothing left to keep — Undo, then make the reference shape smaller
Merge Shape says some reference shapes were skipped	Merge only takes reference shapes of the same geometry type as the target; the rest are left out
Split Shape says it needs a polygon, or needs a polyline	Split needs at least one polygon on the target layer and at least one line on the reference layer
Reshape says it needs a single continuous line	The reference layer must hold exactly one line drawn in one unbroken run; press Reset and draw it again
Reshape reports "does not cross any target shape"	The reference line must cross the target boundary, not merely sit near or inside it
XOR reports a type mismatch	Target and reference must both be polygons, both lines, or both points

Shape Tools

Issue	Solution
Simplify reports no vertices removed	Increase the Distance value — the current deviation is too small to drop any vertices
Offset or Simplify says "Enter a non-zero distance"	The Distance field is empty or 0; enter a value in metres (use a negative value to offset the other way)
Offset went the wrong way	Reverse the sign of Distance — for polygons + expands and − contracts, for lines + is right of the drawn direction
Offset corners are not the shape I expected	Use the arrow on the Offset button to pick Round, Miter, Bevel or Square; the active choice is shown as Corner style: …
Offset reports shapes it could not offset	A polygon contracted past the point where it collapses, or the result became too complex — the shapes are left unchanged
Hull reports it could not build a hull	The shapes are all in a straight line or at a single point; a hull needs shapes spread over an area
To Lines says it needs a polygon	The tool converts polygons to boundary lines — draw or select a polygon on the target layer first
To Polygons says the lines enclose no area	The lines must close a loop (a nearly-closed loop is closed for you, but an open line is not)

Undo, Redo and Reset

Issue	Solution
Undo or Redo is greyed out	There is nothing left to step through in that direction; only the last 20 steps are kept
Redo stopped working after an edit	Making a new change discards the redo history — the Nothing to Redo notice explains this

Export and Save

Issue	Solution
Export issues	Check geometry complexity
Export fails	Ensure MyLayer has valid geometry data
No features exported	Check that MyLayer contains features in the database
MyLayer not in export list	Verify MyLayer was saved under your username
Overlap dialog keeps appearing	Expected when shapes overlap — choose Merge to combine them, Keep Separate to export as-is, or Cancel to edit

Video Tutorials

INFO

Hover a button in the panel to check its name against the clip — the buttons show icons only, and the names used on this page are the tooltips.

Snapping Operation

Intersection Operation

Cut Shape Operation

Merge Shape Operation

Split Shape Operation

Buffer Operation

Shape File Export

KML Export

See Also

• Advanced Editor - Standalone geometric operations (buffer, union, intersect, difference, reshape, hull)
• My Layers Tool - Manage personal map layers created with the Map Editor
• Unified Map Editors - Specialised editors for FPP, Plan Burn, Sketch, and other workflows

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