This article aims to run through a workflow of assigning a coordinate system to data that has one specified, transforming the projected coordinate system to something more appropriate for our end map product, and then projecting any supplementary data into the chosen projection on the fly.
Assigning a Coordinate System on Import
- I begin by importing a shapefile of the County level boundaries of the United States.
Notice that there is not currently a coordinate system associated with the data. By clicking on the “No Coordinate System Specified” link, I am able to assign one.
It is very important to note that by assigning a coordinate system at this stage, I am not reprojecting or transforming the data in any way. I am selecting WGS84 because I know that this data is in WGS84. If I were to assign a different coordinate system here, the data would still be in WGS84 and not what is assigned here.
Spatially Filtering the Data on Import
- The dataset that I am importing is for the whole Unites States and for this map I will only be focusing on a small portion of New York State. For this reason, I am going to use a spatial filter to crop my data down to my area of interest and save my computer from having to import a county-level shapefile of the entire US.
To do this, click the “Use default filtering options” link next to filtering in the Import Dialogue window. This will display the lower window called “Filtering Options”. Click on the box to the left to enable the spatial filter and then click on the icon to set the parameters.
I will be setting the Relationship to Crop using the dropdown box. I will then use the small Earth icon in the top left to specify the bounds of the spatial filter. You can optionally set the bounds using the latitude and longitude of two points.
Maneuver the markers to specify the extents. In this case, I will be centering over New York.
I do not need to be overly concerned about the accuracy of my crop, as long as my area of interest is included. Press OK once this is set. You will also need to press OK to confirm the settings on the previous two dialogue windows.
This will import the cropped data in WGS84.
Transforming the Data
- I don’t want to leave this data in WGS84 for this map so I am going to reproject the map into something more appropriate using the MAP View Editor. To get to the MAP View Editor, double click on the heading above the layer in the MAP Views panel.
On this edit screen, click on the box next tot he greyed out “Perform Coordinate System Transformation”. Click on the “No Coordinate System specified” link to select a coordinate system that you would like to reproject the data into.
I will be selecting the New York Central Zone which is a Transverse Mercator Projection. Click OK to apply the transformation.
"The artwork has now been transformed."
Transforming on the Fly
- Now that our boundary file has been imported and transformed into the coordinate system I would like to use for my map, I need to import my supplementary data. In this case, it will be a few shapefiles of the New York road network.
You can shift-select multiple shapefiles with the Import tool and then click okay to bring them into your document.
This imports the road shapefiles in a separate Map View and results in the art not lining up properly.
In order to very quickly correct this, shift select your data (in this example it is my Highway line data) and drag it into your other MAP View, in this case, “New York”.
The data has automatically transformed “on the fly” to the projected coordinate system of the destination MAP View.