Working with background imagery
|This exercise is included in the tutorial: Setting up your farm or land project|
Online Imagery is available as a 'WMS Service'. 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.
- 1 Start a project in Iowa
- 2 Accessing available Imagery
- 3 Exercise 02 - Downloading Soils from Web Soil Survey
- 4 Exercise 03 - Importing Imagery
- 5 Exercise 04 - Importing Vector data - shapefile format
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®
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 two examples, a low resolution image, and a high resolution image. Enter the following values:
For adding Low resolution Imagery:
* Name: "NASA Global Mosaic"
* Group: "Base Map"
* URL: "http://wms.jpl.nasa.gov/wms.cgi?"
- Your project should look like this
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.
|Warning:||WMS layers availability depends on external servers. This means that there may be times when WMS layers are not available|
Exercise 02 - Downloading Soils from Web Soil Survey
You can use GeoAgro GIS to download soils information directly from the Web Soil Survey, using the WFS Tool. WFS stands for Web Feature Service, and Open Standard that allows to retrieve geographic features from online servers you may visit this WFS Article for more information.
- Zoom in to your Project Area using the Zooming Tools.. Please note: It's convenient to keep the project area as small as possible, to make the soils download faster
- Select the “Soils” layer.
- Click on the “WFS” tool to connect to the soil survey
- In the Importing window, click on the star button to see which servers are available. Now, select “NRCS Soils WGS84 Geographic”.
- The “Layer” dropdown menu shows which layers in the service are available for download. Select “MapUnitPolyExtended”.
- In "Unique values field", select "OBJECTID"
- Click on “OK” and wait for the download to complete.Please note: If the downloading bar does not show any progress, it might be due to the WFS server not responding. Cancel your download and try again.
- Your project should look like the screen below
Exercise 03 - Importing Imagery
To import imagery into GeoAgro GIS it has two requirements:
- GeoAgro GIS supports images in Geographic Coordinates. If you have imagerey projected in other systems, you will need to reproject it, either doing it yourself (see how), or asking GeoAgro for help.
- GeoAgro GIS supports images in these formats.
|Note:||when reviewing supported imagery formats, please note that depending on the type of image format, it may require to have an additional file with georeferencing information (called 'world file')|
Importing imagery in Geographic coordinates
In this exercise we are going to import a sample image:
- Download a sample image from this link (8Mb) and save it to your local disk
Please Note: The file is a zip file, to import the image you should unzip it first
- Select Add new layer tool from the Edition panel
- Choose the Image layer option.
- Fill the fields as below.
- Search in your local disk and select the previously downloaded and unzipped image.
- Now there's a new Layer in the References Panel named "NAIP Orthophoto" under the "Base Map" group.By default, image layers are turned off at import time, please turn it on by clicking the eye icon. The map should look like the one below.
Importing imagery in Projected systems
If you have imagery available which is already projected in a State Plane Coordinate System, you will need to reproject it to Geographic coordinates:
Exercise 04 - Importing Vector data - shapefile format
In this exercise we are going to import a sample Watershed boundary layer in shapefile format.
- Download sample data to your disk from this link, and unzip it to an appropiate folder.
- From Tools for importing data select the Import Layer tool.
- Click on Browse and select the recently downloaded shape file. Please fill the remaning fields as described below:
Group: 'Base Map'
Structure: GeoAgro GIS automatically matches it to the available structure: 'Watershed Boundary'
When a shapefile is imported, GeoAgro GIS reads the current projection information, and reprojects it to a geographic coordinate system WGS84.
- After importing, you'll notice that a new layer "wbdhu12_a_mbr" has been created in the References Panel, with its corresponding polygons in the map area.