Using the Snap tool for measuring or drawing accurately

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Snap tool

The features that are created in GeoAgro GIS are formed by Nodes. If the feature is a polygon or line, it's formed by a series of nodes that give shape to the polygon or line; if it's a point, it will coincide with the node.

The Snap tool enables to use the nodes of all the features included in a layer as a reference, when selecting point on the screen. This is a useful tool that allows to work accurately when used together with measuring tools and drawing tools.

It works in the following way:

  1. Select a layer in the Snap dropdown list on the upper left corner of the screen, as shown in the figure 
  2. Use any drawing or measuring tool - the points that you click on the screen will snap to the nearest reference node of the selected Snap layer

We'll review in more detail how it works with both groups of tools in the next sections.

Snap tool combined with drawing tools

The Snap tool combined with Drawing tools allows to draw accurately, using as a reference nodes from feautres of the same layer or another layer.

In this example, we want to draw a field, using as a reference the field corner points taken with a GPS Navigator.

For this purpose you will need to:

  1. Make visible the field corners layer
  2. Make the layer where the field will be drawn active and visible.
  3. Click on the tool Add new object tool
  4. In the Snap box select the layer with the field corner points

  5. The nodes of the selected layer will be marked in the screen, we will use them as a reference to draw the field in the next step

  6. Finally, click on the nodes that you need to draw the field, doing a double click in the last corner. In this way, the nodes that form the field will be on the same location of the points taken with the GPS navigator.

Snap combined with measuring tools

The Snap tool combined with Measuring tools //LINK allow to measure lengths or areas more accurately.

For example, let's say that you want to measure a polygon area. You'll have to:

  1. Make the layer with the polygon that you want to measure visible.
  2. In the Snap tool select the layer with the polygon that you want to measure

  3. Select the Measure Area tool. //LINK
  4. The nodes of the selected layer will be marked in the screen, we will use them as a reference to measure the area.Image:Mpw_herr_utiles_dibujo_snap_medicion_3.jpg
  5. Click on the nodes that you want to use to measure the area, doing a double click to finalize the area. This way, the nodes that form the measured polygon will be in the same location as the polygon nodes.