Snapping to Feature Geometries

To create topologically consistent geometries, we have the Snap To Features option in our drawing mode settings.

While drawing new geometries, you can snap new points to existing features quickly and easily. This can be helpful when you need topological consistency, for example, when mapping habitats or connecting two lines that make a continuous feature.

Check out the video below to see it in action, or keep reading for more details.

Snapping is disabled by default, so the first step is to enable it. You can access the setting while drawing a new feature by tapping the Settings button on the drawing controls

A split image showing the drawing screen in Touch GIS. On the left the Settings button is circled, and on the right there is an arrow pointing to the Enabled setting for Snap To Features.
Enable the setting by beginning to draw a new feature, and then opening the settings panel.

In addition to the activation toggle, you can set the maximum snap distance in meters. The maximum snap distance controls the search radius for snap targets, so update this value according to the precision required by your project and the map scale that you’ll be working at.

With the setting enabled you can begin drawing your new geometry. As your cursor approaches an existing feature and crosses into the snap region, you’ll notice that your cursor changes, and a new icon is drawn on existing geometry. This icon shows you where the snap target on the existing feature is. It also shows you what type of point the snap target is, whether it’s an edge (plus sign), endpoint (triangle sign), or a non-endpoint vertex (circle). Tapping Add Point will place the point at this snap target.

Three images are shown side-by-side. On the left is a snap icon that is a plus inside of a white circle, drawn on top of an existing line geometry. In the middle the icon is a triangle within a circle, on the endpoint of the line geometry, and on the right is a black circle within a white circle, drawn on a vertex of the line.
A gif of the polygon drawing process with snap to features enabled. It shows a blue polygon being drawn connected to a green polygon on the left. The video starts by connecting the new blue polygon to four vertices of the green polygon.

With this feature, you can draw topologically consistent geometries right in the field in just a few seconds, reducing the amount of cleanup and simplification required back in the office.

You can also snap to features using Free Draw mode. The snap target icon will appear when you tap on the screen to confirm where the point was placed. When dragging your finger or a stylus, once you enter the snap target radius, the next point will automatically be placed on the existing geometry.

Finally, snapping is also available when editing geometries. So you can quickly add a new line or polygon with free draw mode without snapping, and then enable it later to make sure vertices are snapped to the right location.

We’re excited about this new feature, and hope it helps you to create more accurate geometries more quickly in the field.

If you have any feedback on this feature, we would love to hear from you. Please reach out to [email protected].

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