Navigating your maps
In these exercises we'll learn how to move around your map, query your data, select objects, and make measurements
We'll use tools available from the Navigation Toolbar, displayed at the top of the screen
- 1 Download sample data
- 2 Exercise 01 - Moving around your map
- 3 Exercise 02 – Selecting and Querying Data
- 4 Exercise 03 – Measuring
Download sample data
For these exercises we are going to download a sample dataset: 'Sample Farm IA'For this purpose, you can follow the steps detailed in Download sample data, but selecting 'Sample Farm IA' as the initial dataset, which can be found under the 'Tutorials_en' folder:
Exercise 01 - Moving around your map
We'll review different options to move around your map
Double clicking on a layer
By double clicking on a layer, you will: turn the layer on, make it active, and zoom to the layer extent
- In the sample project, double click on layer 'State' - it will zoom to the extent of the State of Iowa
- Now click on layer 'Counties' - It will zoom to the extent of Counties (which of course is the same as the State), and also turn the Counties layer on.
- Now click on layer 'Fields_NRCS' - It will zoom to the Fields digitized in our sample project.
Zooming and Pan
There are different options to zoom around your map in the Navigation Toolbar:
Use the Rectangle Zoom Tool to zoom in or out using a zoom window, draw a rectangle around the Field 'a' to get closer view of that layer.
Go to the Navigation Panel and click on the Show Full Map tool . Next, the maximum extent for the visible layers will be shown on the work window.
Pan Tool - By pressing and holding the left mouse button, you will be able to navigate the map.
You can also search for coordinates by clicking on the GPS coordinate locator, using a GPS coordinate taken from the field, or Google Earth for instance.
After you enter the coordinates, the screen will zoom in to the entered coordinates.
For this example, try entering the following coordinates:
Lat: N 42 15' 38.23"
Lon: W 93 23' 32.8"
Using the Scale
Exercise 02 – Selecting and Querying Data
Several GeoAgro GIS operations require that you first select the features that you will work on. For instance, before modifying, copying, or editing attribute data, you need to select
There are several ways of selecting an object, as you can see when expanding the selection tool.
To select a feature, the order is:
- Make the layer where the feature is located active
- Use one of the selection tools to select a feature
Make the layer 'Fields_NRCS' by clicking on it. This layer contains fields downloaded or imported from the USDA NRCS.
Use the Select Point option and then click on the Field in the upper left corner:
To select contiguous fields, go to the option Rectangle and draw a rectangle that intersects three fields in the figure below:
To unselect both fields click on Remove Selection or click anywhere outside the fields
Another way to select/unselect a field is by holding the Control key pressed while you select.
For instance, try selecting the two fields in the figure using the Point Selection tool , while holding the control key pressed.
Data Querying Tools
Select features in the 'NRCS Fields' layer, and export to excel
Now you will select fields 'a' and 'b' with the Select by Rectangle tool . To do that, draw a rectangle that intersects the mentioned fields :
Go to the Query tool, and select the option 'Quey data by selection'.
The attribute table for the objects you have selected will open.
You will next export the table in Excel format (.xls).
Click on Export and save the table as fields_adc.xls. Then click OK.
Exercise 03 – Measuring
Double click on the layer called 'Tracts' under the 'Map Layout' group.
Click on the upper left corner of the field 'a' and then double click on the upper right corner of it. You will automatically see the segment defined with the measured distance.
Length units can be selected right there. By default, GeoAgro GIS shows length in feets.
You will now calculate the area of the same field expressed in acres.
By clicking on each vertex of field 'a', and double-clicking on the last vertex that closes the plot, the surface of the polygon that has been created will be shown in acres.
The area units can also be selected right there.