Geo-Referencing an Unreferenced Map
Overview
If you have drawn your map without real world coordinates (latitude and longitude), you may want to geo-reference it in Farm Trac+ so that it lines up with the USGS Road & Waterway data. This would be the case if you created your map with an older version of Farm Trac (versions older than 9.0) using scanned FSA maps. Adding Real World Coordinates to an existing drawn map will adjust your entire drawn map based on known coordinates.
In order for a proper conversion, your existing maps should have been drawn to scale. If your map is not accurately drawn to scale, we recommend that you recreate your map from scratch so that an accurately drawn map can be obtained.
Using U.S. Geological Survey road & waterway maps (USGS) is the best way to reference these maps.
Geo-referencing Maps using USGS Maps
Maps that have been created by the United States Geological Survey (USGS) can be used to geo-reference unreferenced maps. These maps are available on a CD that came with your copy of Farm Trac+. These maps include actual coordinates and will be displayed to scale in Farm Trac+.
Registering a 0,0 Coordinate
The first step for geo-referencing maps is to register a 0,0 coordinate on the drawn map. Use the Geographic Coordinate tool (select Preferences from the File menu then select Geographic Coordinates) to register this coordinate on any spot of the map. Once this is done, the next step is to load the USGS maps into Farm Trac+. The Map Setup function is used for loading this data. Please refer to the helps, tutorial, or the section on "Creating a Map" in this manual for more information.
Register Coordinate on the USGS Maps
Once the USGS maps are imported, it is time to find a coordinate from those maps. This coordinate will be used to register the unreferenced map.
The only layer(s) that should be displayed on the screen when locating the coordinate are the USGS Road & Waterway layers. All other layers including the Main Farming Layer should be removed from display. This is done through the Layers tab on the left.
To register the coordinates, you will need to locate a position on the USGS maps that is also on your drawn map. This will normally be an intersection of two roads or the intersection of a road and waterway. Zoom in as tight as possible on the location to register. Using the Registration Points tool from the Backdrop Tools, click on the point to be registered. The coordinates will automatically be displayed, but the name of the coordinate, such as the name of the intersecting roads, will need to be entered. Press Record to save the point.
Use Registered Coordinate for Drawn Map
Once a known intersection from the USGSmaps has been registered, this same location on the main farming layer needs to be entered. This will move the unreferenced map to the specified geographic location. Display only the Main Farming layer. Do not have the USGS maps on the screen. These can be removed through the Layers tab on the left.
To register the coordinate, first zoom in as tight as possible on the area to register on the drawn map (the road or waterway intersection). Then use the Geographic Coordinates tool (select Preferences from the File menu then select Geographic Coordinates) and click on this position.
The registered points just created will appear. Choose the appropriate point and the coordinates will automatically be displayed.
When using USGS maps and registering coordinates, do not select the option to have the coordinates Affect All Layers. If this is selected, the USGS layers will be changed and will have to be deleted and imported again so that they have the correct coordinates. If the Affect All Layers option is not chosen, then only the current top/Active Layer (as displayed in the Layers tab on the left) will be affected by the coordinates. Once the coordinates are registered on the unreferenced map, the map may disappear from the screen. Choose Zoom All to re-display it.
Changing a Drawn Map to Correspond with USGS Roads and Waterways
Once the maps are geo-referenced, the next step is to move and edit the fields to correspond with the USGS maps. Using a "Get from the Web" image is the best way to do this.
To redraw fields using an internet image, you will first need to use the Get from the Web tool to download the imagery. This feature is discussed in more detail in another chapter of this manual as well as in the tutorials and helps. Once the image is loaded it can be used to help move, draw, and edit fields. The best way to edit the boundary of a field will be to select the Edit Points Tool (from the Mapping Tools). You can then click inside a field to get points around the boundary that can be moved.