A graticule is the network of lines of latitude and longitude drawn at regular intervals on a map. Graticules are created in MAPublisher using the Grids and Graticules tool. In some maps, you may want to limit the area on the map that a graticule covers. For example, you may want it to cover only the map’s area of interest. The image below is a map of North America with a graticule drawn at 5-degree intervals. US State boundaries are drawn in white. In this post, we’ll modify the graticule three times so it conforms to the edges of the image, so it covers only the Continental United States, and lastly a combination of the previous two modifications.
MAPublisher can limit the geographic extents of a graticule in two ways: using Grid Bounds and using Grid Constraints. In both cases, you’ll specify the lower left and upper right corners of the graticule. Specifying Grid Bounds will limit the extent of the graticule to a rectangular area while specifying Grid Constraints will limit the graticule along lines of latitude and longitude. If both Grid Bounds and Grid Constraints are specified, the graticule will cover an intersection of the two areas. The image below shows bounds and the constraints and the intersecting area which forms the graticule.
To modify a graticule so that it conforms to the edges of the image, you’ll need to specify grid constraints. In the Grids and Graticules dialog box, click the Specify Grid Constraints check box and set the Lower Left and Upper Right corners to the corners of the image which are -127°, 7° and -50°, 65° respectively.
To create a rectangular graticule covering only the lower 48 states, click the Specify Grid Bounds check box and set the Lower Left and Upper Right corners to the corners of that area. Tip: click the MAP World Locations drop-down arrow to choose the values for the lower left and upper right corners.
When both Specify Grid Bounds and Specify Grid Constraints check boxes are both checked, the graticule will cover an intersection of each of the extents. For instance, in the map below, the northern extent follows the 49th parallel at the Canadian border, the western extent is at the edge of the image (127° west) and the south and east extents are the same as in the previous map.
Ever have the problem that you want to make a map and you are waiting on the final extent or scale, but you want to get started adding data and working on the layout? Here are a couple of tips to make your life easier.
1. Move artboards around without moving your data
Geographic features in Adobe Illustrator are generally referenced to a known coordinate system. This coordinate system is mapped to Adobe Illustrator’s “Global Coordinate System” which has its origin at the top-left corner of the first artboard in a document. What this implies is that artboards can be moved around within this reference system in order to show different geographic data on the page. However, by default, moving an artboard moves any art that overlaps it as well. Obviously moving any referenced data around is going to ruin its spatial accuracy so this is something we want to avoid. Luckily there are two ways of doing this.
The first is to select the Artboard tool and click the Move/Copy artwork with artboard button to the right of the artboard name in the control panel above the document window.
With this option turned off, you are free to move the artboard around without disturbing any of the geographic data.
There is one downside to this though: you may have map elements such as titles, legends, grids, masks etc. that you want to stay locked in place on the artboard while you move it around the geographic data. The easiest way to do this is to simply lock any layers that contain geographic features, unlock the map elements, and activate the Move/Copy art with artboard option.
When the artboard is repositioned, your data will stay in the correct geographic location and your map elements will move with the artboard, keeping the same relative position.
2. Set up a clipping mask in conjunction with a grid
The previous example used a white polygon with a hole in the middle as a mask to provide whitespace around the edge of the map. Another way to achieve this is to use a clipping mask to hide geographic features outside the extent of the mask. This works well by itself, or when combined with a grid or graticule layer.
We have taken the previous example, deleted the mask and adjusted the colour of the background polygons slightly. We have also added an AOI polygon that will serve as the clipping mask extent.
To create a clipping mask, the first thing we’ll make a new layer called Clipped. Make sure that it is a non-MAP layer (verify this in the MAP View panel).
Next, drag both the AOI layer and layers that contain geographic data into the Clipped layer making sure that the AOI rectangle is above the layer holding the geographic features.
Now if we select the Clipped layer and click on the Make/Release Clipping Mask button (Second from the left at the bottom of the panel) we should see the AOI rectangle become invisible and the MAP layer is visible within the extent of this path.
We can now add a grid over the top of the clipped area using the Grids & Graticules tool. You will find that the default extent of the grid is the same as the spatial data. You will need to resize the grid to match the clipping mask.
If you want to change the spatial extent of the map you have to adjust both the clipping polygon and the grid. It would be nice to group them and resize it together, but Adobe Illustrator doesn’t allow groups to span multiple layers. One way around this is to use a saved selection. To do this, select the clipping mask and the MAPublisher Grids, then choose Select | Save Selection. Give the selection a name like Grids and Clipping Mask.
Now if you need to adjust the spatial extent of the map you can quickly choose the saved selection and resize the clipping mask and grid or move them both around the artboard simultaneously.
In MAPublisher, the grid bound is the visual extent of the grid or graticule. The grid constraint is the geographic extent of the grid or graticule. It may be a little confusing since both grid bound and grid constraint are defined by coordinate values. In terms of hierarchy, think of the grid bound as the overall container of the grid and the constraint as being contained within the bound.
These examples may help you better understand it.
1. In this example, the grid bounds are specified as the lower-left and upper-right of the artboard corners. Notice that the graticule extends all the way to the edge of the artboard (as specified). This is a very typical way to use a grid or graticule.
2. Here, the grid bounds are still the lower-left and upper-right of the artboard. The grid constraint is based on the minimum and maximum longitude and latitude values of the specified MAP Locations. Notice that the rectangular black border of the grid bound is at the edge of the artboard. This is also a common way to use a grid or graticule, especially for larger scale maps.
3. In this example, the grid constraints were disabled and, instead, the two MAP Locations are used to define the grid bounds. Notice that the rectangular black border of the grid bound is defined by two MAP Locations.
4. When both grid bound and grid constraint are set to the same coordinates (in this case, MAP Locations) you can see the result here. The grid bounds are clipping the grid constraints. This would not be an ideal situation to use grid constraints, but it is definitely possible to use it in this fashion.
MAPublisher Grids & Graticules are highly customizable and we’ll be blogging more about its features.
In a previous blog about Grids and Graticules, we quickly introduced one of the major features of the new Grid and Graticule tool. We’d like to share another major feature when creating grids: creating grids with an alternative coordinate system.
For example, the MAP View has a coordinate system “NAD 83 / UTM zone 17N” (in metres). You might want to make grid lines with the same coordinate system but in different units. You can do so by creating a custom coordinate system and then specifying the desired unit (US Foot, for this example), then creating a grid based on custom coordinate system. In this example, a grid with NAD83/UTM zone 17N (metres) coordinate system is created in the blue colour. Another grid with a NAD83/UTM zone 17N (USFoot) custom coordinate system is created with the orange colour.
Likewise, you can create multiple sets of measured grids with different coordinate systems in one MAP View (e.g. one set with NAD83 UTM, another with NAD27 UTM, another with some other local coordinate system) without the need to transform the MAP View.
If you haven’t noticed yet, we released an enhanced version of the Grid and Graticules tool (MAPublisher 8.7 and higher). With the new Grid and Graticules tool, you will find that you can export grid settings and save them. Most importantly, these grid settings files can be shared and imported to another document.
Once a grid is created, save the settings to a *.cfg file. Two configuration files are created per grid: grid settings and label settings.
Grid settings configuration files store information for all related grid options (e.g. ticks, intervals, offsets, borders). Label settings configuration files store information for all related label options (e.g. axis labels, fonts, styles), even for multiple grids. Label settings are saved with _labelData suffixed to the file name.
Share the files and load the *.cfg file in the Grid and Graticules dialog box.
Some of the major functions of the new Grid and Graticules tool are adding tick marks along border lines, placing cross hair symbol instead of lines for grid/graticule lines, styling lines and text more flexibly, and having more label options available. You can share the settings by exporting one and importing to another document as well. You can make a set of grid lines looking like this below.