Working with Layers
From Wikiagro.com
| This exercise is included in the tutorial: Getting Started with GeoAgro GIS |
Much like any other GIS, GeoAgro GIS presents geographical entities as a series of overlaid maps that are called "layers". Learn how to use the Reference Panel to work with them.
Contents |
Setup a Sample Project
For these exercises we are going to create a sample project, using the dataset: 'Sample Farm MO'
The system starts showing the Projects Panel
Click on Create, and enter a name for the project, for this example: Sample Farm MO. Check option "Retrieve startup data for your project"
| Note: | Please make sure to Check on the option "Retrieve startup data for your project", when you want look for available datasets. |
For our exercise we will go into the Tutorials Folder, and select the file: Sample Farm MO.gis
After download is completed, it will show you the option to import the downloaded dataset into your project. Check on Restore, and then Click on Import 
It will create default data layers and attributes for your farm project. These layers/attributes can be customized for your needs as well.
After the Import is complete, you will see the Map of the downloaded State or Region, in our case, the State of Missouri.
- On the References Panel on the left, expand the Administrative Divisions Group, double-click on the States layer
, and it will show the whole State
- On the References Panel on the left, expand the "Base Map" Group, double-click on the Sample Imagery NAIP layer
,
and it will zoom to our Sample Farm project area.
|
| Note: | If you had issues downloading this sample data, as alternative you may also try downloading the dataset from this link, and restore it following the instructions in the Restore Backup tool |
|
| Note: | When working in the project panel, if you do not see a project, please try expanding the project tree by clicking on the "+" symbol next to the root of it. |
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How layers are organized
Layers are organized in Groups. Click on Groups at the left reference panel a couple of times. all the layer groups will expand or collapse as shown in the following figure. 
»» 
Click on one of the groups, for instance Base Map, and you will see the layers under this group
Changing the position of a Layer or group of layers.
The position of a Layer determines if it's visible. For instance, let's turn on layers: Sample Imagery NAIP, and Sample EDRG
Layer Sample Imagery NAIP is visible
Now let's move layer Sample EDRG on top of the layer Sample Imagery NAIP, just by clicking on it and dragging it to a position above.
Now layer Sample EDRG is on top and visible.
You can also do the same regarding the position of a Group of Layers. For instance, click on any Group o layers and drag it on top of another Group name.
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Making a Layer active, visible, or invisible
Only one layer can be 'active' at the Reference Panel, to see which layer is active it's name has a light-green background. To make a layer active, just click on it's name
In GeoAgro GIS, operations and commands are executed on the active layer.
Double-click on layer Counties to show its full extent
To make it invisible, click on the corresponding eye icon and clear the visibility checkbox
The eye icon will change it's color to grey
»» 
And Counties will not be visible on the map
To make Counties visible again, please click again on th eye icon and check the visibility checkbox. »»
And Counties will be visible on the map
You can also hide or show an entire group of layers, by clicking on the checkbox next to the group's name.
»» 
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Layer status: invisible, visible, active
Layer's transparency
let's change the transparency of layer Sample EDRG, to view the imagery below. Click on the eye icon and then move the sliding bar.
Now the layer Sample EDRG is partially visible, and Sample NAIP Imagery can be seen.
Sometimes a layer may be visible but is not seen because there is another layer on top.
For this reason, it's a common practice to order the layers following these tips.
- Point and Polyline layers on top.
- Below them the Polygon ones (but you can always use hollow Polygons).
- And at the bottom the Raster layers, such as Topographic maps (DRGs) and Satellite imagery.
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| This exercise is included in the tutorial: Getting Started with GeoAgro GIS |
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