Working with background imagery
One of the first steps in your farm/land project is to access background imagery.
One of the options to access online Imagery in GeoAgro GIS, is the use of 'WMS Services'. WMS stands for Web Map Service - a standard protocol for serving georeferenced map images over the Internet that are generated by a map server using data from a GIS database. Please visit this WMS Article for more information.
Usually, WMS Sources come from public providers such as government organizations, making their data publicly available. These are examples of WMS Sources that can be accessed using GeoAgro GIS.
Start a project in Iowa
First, create a sample project using the State of Iowa dataset, as detailed in this tutorial
Accessing available Imagery
- Double Click on the 'States' layer to see a full view of the State
- Zoom in to the lower left corner of Hardin County
- Click on the 'VE Imagery' Layer to turn on Imagery from Bing Maps®. If it doesn't refresh, use the Pan tool to move the view a bit, and refresh the imagery.You should now see aerial imagery from Bing Maps®
You can, alternatively, use the 'Imagery - NAIP' Layer from the USDA National Aerial Imagery Program (NAIP) and 'Imagery - EDRG' layer to see the available Topography scanned sheets (EDRGs or Digital Raster Graphics). There are still issues in connecting with these sources so you may or may not see it depending on the location you are working on.
Turning on layer 'Imagery - NAIP':
Turning on layer 'Imagery - EDRG' (Digital Raster Graphics - Topography layer) :
Saving your imagery to work offline
It's very important to be able to work with imagery offline. Once you have selected your project area, it's a good idea to save the imagery (aerials, topo or other) as offline layers, which will provide faster performance, or the ability to work disconnected from the internet from the field or other disconnected locations. For this purpose you can follow the steps in this article: Save the WMS image to use it offline
Accessing Imagery available from other WMS Sources
This option will be useful as more imagery become publicly available on the internet as a WMS service. These may be provided by government or private organizations. A list of WMS Sources that you may use in GeoAgro GIS is available here.
- On the right panel, click on the Create New Layer option . Add a WMS Layer, by following these instructions. We are going to add an example of low resolution image available from NASA. Enter the following values:
* Name: "NASA Global Mosaic"
* Group: "Base Map"
* URL: "http://wms.jpl.nasa.gov/wms.cgi?"
- Your project should look like this
|Warning:||WMS layers availability depends on external servers. This means that there may be times when WMS layers are not available|