Difference between revisions of "Using the Snap tool for measuring or drawing accurately"

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(Snap tool combined with drawing tools)
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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'''.  
 
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 the following way:
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It works in the following way:  
  
#Select a layer in the Snap dropdown list on the upper left corner of the screen, as shown in the figure [[Image:UDT2.jpg]]
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#Select a layer in the Snap dropdown list on the upper left corner of the screen, as shown in the figure&nbsp;<br>[[Image:UDT2.jpg]]  
 
#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
 
#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
  
 
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<br>
  
 
We'll review in more detail how it works with both groups of tools in the next sections.  
 
We'll review in more detail how it works with both groups of tools in the next sections.  
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<br>  
 
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== Snap tool combined with drawing tools  ==
 
== Snap tool combined with drawing tools  ==
  
The '''Snap'''&nbsp;tool combined with Drawing tools allows to draw accurately, using as a reference nodes from feautres of the same layer or another layer.
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The '''Snap'''&nbsp;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.
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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:
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For this purpose you will need to:  
  
#Make visible the field corners layer<br>[[Image:Mpw herr utiles dibujo snap dibujo 1.jpg|Image:Mpw_herr_utiles_dibujo_snap_dibujo_1.jpg]]&nbsp;<br>
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#Make visible the field corners layer<br>[[Image:Mpw herr utiles dibujo snap dibujo 1.jpg|Image:Mpw_herr_utiles_dibujo_snap_dibujo_1.jpg]]&nbsp;<br>  
#Make the layer where the field will be drawn active and visible.<br>
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#Make the layer where the field will be drawn active and visible.<br>  
#Click on the tool [[Add_New_Object|'''Add new object'''&nbsp;]]tool<br>
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#Click on the tool [[Add New Object|'''Add new object'''&nbsp;tool]]<br>  
#In the '''Snap '''box select the layer with the field corner points<br>[[Image:Mpw herr utiles dibujo snap dibujo 2.jpg|Image:Mpw_herr_utiles_dibujo_snap_dibujo_2.jpg]]<br><br>
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#In the '''Snap '''box select the layer with the field corner points<br>[[Image:Mpw herr utiles dibujo snap dibujo 2.jpg|Image:Mpw_herr_utiles_dibujo_snap_dibujo_2.jpg]]<br><br>  
#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<br>[[Image:Mpw herr utiles dibujo snap dibujo 3.jpg|Image:Mpw_herr_utiles_dibujo_snap_dibujo_3.jpg]]
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#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<br>[[Image:Mpw herr utiles dibujo snap dibujo 3.jpg|Image:Mpw_herr_utiles_dibujo_snap_dibujo_3.jpg]]<br><br>
 +
#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.<br>[[Image:Mpw herr utiles dibujo snap dibujo 4.jpg|Image:Mpw_herr_utiles_dibujo_snap_dibujo_4.jpg]]
  
 
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<br>  
  
6- Finalmente, hacer un clic sobre los nodos que necesite para dibujar el lote, teniendo presente que se debe hacer doble clic en el ultimo nodo para cerrar el polígono. De esta manera, los nodos que forman el lote quedarán en la misma posición que los puntos tomados con el navegador GPS en los esquineros del mismo.
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== Snap combined with measuring tools ==
  
[[Image:Mpw herr utiles dibujo snap dibujo 4.jpg|Image:Mpw_herr_utiles_dibujo_snap_dibujo_4.jpg]]
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The Snap tool combined with Measuring tools //LINK allow to measure lengths or areas more accurately.
  
<br>
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For example, let's say that you want to measure a polygon area. You'll have to:
  
=== La herramienta Snap combinada con las Herramientas de Medición  ===
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#Make the layer with the polygon that you want to measure visible.<br>[[Image:Mpw herr utiles dibujo snap medicion 1.jpg|Image:Mpw_herr_utiles_dibujo_snap_medicion_1.jpg]]&nbsp;<br>
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#In the Snap tool select the layer with the polygon that you want to measure<br>[[Image:Mpw herr utiles dibujo snap medicion 2.jpg|Image:Mpw_herr_utiles_dibujo_snap_medicion_2.jpg]]<br><br>
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#Select the Measure Area tool. //LINK<br>
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#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|Image:Mpw_herr_utiles_dibujo_snap_medicion_3.jpg]]<br>
 +
#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.<br>[[Image:Mpw herr utiles dibujo snap medicion 4.jpg|Image:Mpw_herr_utiles_dibujo_snap_medicion_4.jpg]]&nbsp;
  
La herramienta '''Snap '''combinada con las [http://wikiagro.com/es/Categor%C3%ADa:Herramientas_de_Medicion '''Herramientas de Medición'''] permiten agregar exactitud a las mediciones (recordemos que las mediciones tomadas con las [http://wikiagro.com/es/Categor%C3%ADa:Herramientas_de_Medicion '''Herramientas de Medición'''] tienen un factor de error determinado por el nivel de zoom de la capa).
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Supongamos que queremos medir la superficie de un polígono, para ello deberá:
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1- Poner visible la capa que contiene el polígono a medir.
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[[Image:Mpw herr utiles dibujo snap medicion 1.jpg|Image:Mpw_herr_utiles_dibujo_snap_medicion_1.jpg]]&nbsp;
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<br>
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2- En la herramienta '''Snap''' elegir la capa que tiene los polígonos a medir.
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[[Image:Mpw herr utiles dibujo snap medicion 2.jpg|Image:Mpw_herr_utiles_dibujo_snap_medicion_2.jpg]]
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<br>
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3- Elegir la [http://wikiagro.com/es/Categor%C3%ADa:Herramientas_de_Medicion '''Herramientas de Medición'''] deseada, por ejemplo [http://wikiagro.com/es/Medir_superficies '''Superficie'''].
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4- Aparecerán una serie de puntos amarillos en el mapa, esos puntos amarillos son los nodos que componen los objetos de la capa elegida en el paso 2 (en este caso son los nodos en base a los cuales se dibujaron los polígonos de la capa).<br>[[Image:Mpw herr utiles dibujo snap medicion 3.jpg|Image:Mpw_herr_utiles_dibujo_snap_medicion_3.jpg]]
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<br>
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5- Finalmente, hacer un clic sobre los nodos que necesite para armar el polígono de medición, teniendo presente que se debe hacer doble clic en el ultimo nodo para cerrar la medición. De esta manera, los nodos que forman el polígono de medición quedarán en la misma posición que los nodos que forman el polígono, con lo cual la medición es exacta.
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[[Image:Mpw herr utiles dibujo snap medicion 4.jpg|Image:Mpw_herr_utiles_dibujo_snap_medicion_4.jpg]]&nbsp;
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[[Category:Reference_guides]] [[Category:Navigation_Toolbar]] [[Category:GeoAgro_GIS]]
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[[Category:GeoAgro_GIS]]

Revision as of 18:54, 11 August 2012


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 
    UDT2.jpg
  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
    Image:Mpw_herr_utiles_dibujo_snap_dibujo_1.jpg 
  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
    Image:Mpw_herr_utiles_dibujo_snap_dibujo_2.jpg

  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
    Image:Mpw_herr_utiles_dibujo_snap_dibujo_3.jpg

  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.
    Image:Mpw_herr_utiles_dibujo_snap_dibujo_4.jpg


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.
    Image:Mpw_herr_utiles_dibujo_snap_medicion_1.jpg 
  2. In the Snap tool select the layer with the polygon that you want to measure
    Image:Mpw_herr_utiles_dibujo_snap_medicion_2.jpg

  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.
    Image:Mpw_herr_utiles_dibujo_snap_medicion_4.jpg