Using the Coreo Geometry Features and Tools

9 minutes

In this document we’ll cover the different geometry tools available to support data collection in the Coreo app, and look at how to use them.

Note

The tools you will see in your project depend on the geometry types that your form is set up to use. For example, your project might be configured to only allow the recording of point location data. In this case, you will not see any of the tools which support the editing of polygons, such as the Cutout, Split and Merge tools.

Adding a location feature

If your project supports more than one type of geometry, first select the one you need, using the dropdown in the upper left corner of the screen. If you only have one type available in your project, this will be automatically selected.

Point

The Point feature is very straightforward to use.

To position your data point simply move the crosshairs to the desired location and tap the Add Point button in the bottom right (shown below).
If you are happy with your placement tap the Next/Done button to continue.
Should you wish to change the position of your dropped point, tap the ‘tick’ icon, then tap on your point to drag it. A drag handle will appear to make this easier.

MultiPoint

This feature allows you to place multiple points associated with a single record. The process is identical to that outlined above. However, on completion of your first point, you will be prompted to drop another. If available in your form you can select it from the geometry dropdown menu in the top left.

Polygon

The polygon feature allows you to draw an area on the map. There are two ways you can draw your polygon:

By dropping points
By freehand drawing a line using the Draw tool

Method 1 – Dropping Points

Once you have selected Polygon using the upper left dropdown, find the location where you wish to draw your polygon on the map.
Move the crosshairs to your start location and then tap the Add Point icon to drop your first point.

Move your crosshairs to the next location and press the Add Point icon to drop another point. A line connects the two points.
Repeat this until the polygon is your desired shape.

You will be alerted if sections of your polygon overlap and are invalid. These will be shown highlighted in red.

When you have built out a valid shape the Confirm Geometry (tick) icon on the right of the screen will become available. Tap this if you are happy with your shape to finalise it.

Now that your polygon is complete you can manipulate it further, in order to refine its shape.

You can tap any of the points to select them.
Once selected you can then drag them to your desired location, either by holding the point itself or the black drag handle attached to it.
You can add new points to your polygon. To do this, move the crosshairs onto the edge of your polygon and you will see the cursor snap to the line.
Tap the Add Point icon to drop another point.

Method 2 – The Draw Tool

To use the Draw tool, you must again either be working with a polygon or line.

Select the Draw (pencil) icon above the Add Point tool

Once selected, the Draw tool’s icon will highlight blue and the Add Point tool will become unavailable.

Note: If you wish to switch back to the Add Point tool simply tap the draw tool again

Draw out the shape of your polygon, either using your finger, a stylus or, if using the app in a browser, your mouse.
A preview of the shape will be shown in red as you draw.

You can adjust the number of points used to define your polygon by adjusting the “Simplification amount” in Settings (white cog icon)

The higher the simplification amount the fewer points on the polygon.

Once complete you will see the number of vertices increase or decrease depending on the set simplification amount.

Note: This tool does a lot of calculation in the background and is not a simple linear relationship. Therefore, you may see points increase or decrease in a non-linear fashion.

As with the previous example, you can select and manipulate individual points, as required. If you wish to remove any points, select where you wish to start removing and then tap the Bin icon.

Overlap Avoidance Tool

An additional option you have available when drawing polygons is to use the “Overlap Avoidance” toggle. As the name suggests, this will prevent your new polygon from overlapping with existing geometries.

Note: This tool only works with polygons of the same layer. If you wish to avoid gaps and overlaps with shapes in another layer you must use the Snap tool (see below).

To use the Overlap Avoidance tool:

Toggle it on by tapping the icon with overlapping shapes shown below. The icon will turn blue, showing that it is active.

Draw a polygon which, in part, overlaps another polygon. Any overlaps will be removed automatically, creating a clean join between the two shapes.

Snap Tool

Another useful tool for the accurate placement of polygons is the Snap tool. This tool allows you to snap your polygon to existing vector features such as area and linear records or to map layers such as redline boundaries. You also have the option to snap to the base mapping, where this is a vector map (such as Streets).

To use the Snap tool:

Tap the Snap tool icon (magnet) to toggle it on.

The icon will highlight blue.

To configure the way the tool behaves go to Settings.

Tap the Settings (cog) icon on the left hand side of the screen

Here you can enable the tool to ‘Snap to base layer’ (only relevant for vector based maps).

You can also adjust the Snapping tolerance. This governs how close to a feature you need to be before the tool will snap to it. Less means you have more fine grained control and you need to approach a line closely before it will snap. More, will enable the tool to snap at greater distances.

Drag the marker to your preferred tolerance level and then test with the polygon tool

To draw your polygon using the Snap tool either position the crosshairs near to an existing geometry or base map feature, or draw with your stylus in close proximity.

Your line or point will snap to the nearest vertex or line segment.

Multiple Polygons

Allows you to add multiple, disparate polygons to a single record. The tools are identical to those outlined above. However, on completion of your first polygon you will be prompted to draw another. If it’s an option in your Project you can select it from the geometry dropdown menu in the top left.

Additional Polygon Tools

There are five additional ways for you to edit your polygons. With a polygon selected you will see a Wrench icon in the upper right corner.

Tap the Wrench icon to reveal the available options.

The Cutout Tool

This tool allows you to cut out a section from your polygon and create inner rings. This is useful for excluding certain geographical features from your polygon such as lakes, areas of woodland and so on.

Select the Cutout tool.

You now have the option of using the Add Point tool or Draw tool to draw the shape you want to cut out. These act in exactly the same way as they would when creating a standalone polygon.

Draw the area you wish to remove.

You can remove sections from both the middle of your polygon and the edges.

When you are happy with the area you wish to cut, tap the blue ‘Complete Cutout‘ button

The Split Tool

The Split tool allows you to split an existing polygon into two separate polygons.

Select the Split tool from the toolbar.
Draw a line across your polygon by dropping two nodes or by using the Draw tool. Make sure that your line entirely bisects the polygon.

Once you’re happy with your line tap Complete Split.
The resulting polygons can both be manipulated as normal
If you have Polygon set as your geometry type you will be prompted to delete one of the new polygons or to switch to MuliPolygon.

The Merge Tool

The Merge tool allows you to add area to an existing polygon.

Select the Merge tool.
Draw your new area ensuring there is some overlap with the existing polygon you wish to add it to.

When happy, tap Complete Merge and your newly drawn area will be incorporated into the existing area.

The Diff Tool

The Diff tool enables you to remove overlaps from a selected polygon. If your selected polygon overlaps with multiple neighbouring areas, the Diff tool allows you to remove them from one polygon at a time.

Make sure that the polygon containing the overlap is selected as shown in the image below.
Choose the Diff tool from the toolbar.
Tap on the polygon from which you wish to remove the overlap.

Any overlaps will be removed to create a precise fit with the neighbouring geometry.

The Diff All Tool

This tool is similar to the Diff tool. However, it will remove all overlaps from your selected polygon in one go without requiring any selection.

Make sure that the polygon containing the overlaps is selected as shown in the image below.
Tap the Diff All tool

All overlaps will be removed, creating a precise fit with any adjoining polygons.

LineString

The LineString tool allows you to draw an open line on your map. Once selected you can use either the Add Point tool or the Draw tool to create your line.

MultiLineString

Like the other Multi options, this allows you to have multiple line strings associated with a single record. The process for adding them is identical to that outlined above. However, on completion of your first line you will be prompted to place another. Where this is an option in a project, you can select it from the geometry dropdown menu in the top left corner.

For more context on how these may be used in a project see our How to guides for UKHab.

Was this article helpful?

Thanks for your feedback!