Georeferencing an Adobe Illustrator document with MAPublisher

If you are using an existing Adobe Illustrator file that was created without the use of MAPublisher, then it does not contain any geographic parameters. The following step will enable you to georeference your Adobe Illustrator document and ultimately create an attribute-rich, accurate scale and world grid structure for your map. Please familliarize yourself with the main MAPublisher functions and in particular those in the MAP Views section of the MAPublisher User Guide (chapter 4) before proceeding.

Before beginning to georeference an Adobe Illustrator file, you must be in posession of the following information:

• The map scale in the Adobe Illustrator file (e.g. 1:25,000 etc.)
• Details of the coordinate system the data is in (e.g. World Robinson projection, WGS84 geodetic system, WGS84 UTM Zone 32 N, etc.)
• The XY coordinates of one tie-in point in the coordinate system on the map in the Adobe Illustrator document
• Finally, the MAP rotation angle value.

1: Determine the map scale

To determine the real world scale of your map, use the scale bar drawn on the map for reference (measure the page size using the Adobe Illustrator Measure tool or MAPublisher meaurement tool and divide by the scale size indicated - make sure to use the correct measurement units). If no scale bar is available, try measuring distances in page units in Adobe Illustrator and compare with the same distance measured in real units with mapping or GIS software, beware that differences in coordinate systems may affect the distance measurements.

An example of the scale shown in an existing map. The scale is 1:250,000.

2: Determine the coordinate system of the map

Determining the coordinate system of the map may be difficult. If no information is provided as metadata or in the map legend, try to compare with other maps of the same area or with traditional coordinate systems used in the area (e.g. US State Plane zone matching a county name in the USA).

Below is an example of the coordinate system shown on an existing map. The coordinate system of the map is UTM (Universal Transverse Mercator) Zone 18. The projection used for the map is Transverse Mercator and the geodetic system used for the map is NAD (North American Datum) 1983.

3: Obtain XY coordinates of one tie-in point (a MAP anchor point)

The XY coordinates of one tie-in point is called a MAP Anchor point in MAPublisher. The purpose of the MAP Anchor point is to make a connection between a real world coordinate and an Adobe Illustrator document page anchor.

To determine a tie-in point, find a specific location in your document for which a real world coordinate location is known or can be easily determined (such as known feature or grid or graticule crossing positions). If grid or graticule lines are not available on the map, you may find a known location such as an intersection of roads and a corner of a building. Record the location of this point in real world coordinates. You can use the values from Eastings and Northings or latitude and longitude if the map is in a projected coordinate system.

Below is an example of the selected anchor point based on the grid lines along the projected coordinate system: (400000 and 5350000 metres for the eastings and northings, respectively).

The coordinate values from the document can be obtained from the Info panel (Window > Info from the Adobe Illustrator menu). Simply open the Info panel and place the mouse on the point where the XY coordinate values were collected earlier. For this example, the XY coordinate values for the document is 0.553 and 0.894 (inches) for X and Y, respectively.

4: Determine the rotation angle of the map

MAPublisher uses the rotation angle value based on the angle of the north arrow, more specifically the true north (cartographic north). If the north arrow of the map is pointing the top of the document (with a right angle), the map in your document has no rotation angle (MAP (A) below - rotation: 0 degree). If the north arrow on the map is tilted, the map of the document has a rotation value with it (MAP (B) and (C)).

When the north arrow angle moves clockwise, the rotation value will be negative (MAP (B) below - rotation: -20 degree).
When the north arrow angle moves counter-clockwise, the rotation value will be positive (MAP (C) below - rotation: 161 degree).

Example case: converting a map to a georeferenced map

I have a map in PDF format that was created a few months ago. I opened the file in Adobe Illustrator and (as expected) there is no georeference information because it was not created with MAPublisher. To georeference the document, I'll begin to collect the four key pieces of required information.

When I looked at the map very closely, one section of the map indicates the georeference information we need.

1: The scale of the map

• The scale of the map is 1:7,000.
  
  

2: The coordinate system of the map

• The coordinate system of the map is NAD 83 UTM Zone 17 N
  
  

3: XY coordinate values of the anchor point from the real world and the document

• This map does not contain the graticule lines or the grid lines from the UTM coordinate system.
  
  
• I selected one of the road intersection on the map. The page coordinate of the intersection is 3.632 and 2.4329 (inches) for the page X and Y, respectively.
  
  
  
  

• In order to collect the real world XY coordinate values of this intersection, I could use a topographic map (like the one from National Topographic System map) or an application like Google Earth.
  
  Find the same intersection as the one specified in the map. The latitude and longitude values of the intersection in the real world are collected (44.3513336 and -78.296358, respectively). These latitude and longitude values are in WGS84 because Google Earth uses WGS84 for the geodetic cooridinate system.
  
  
  
  

4: The rotation angle of the map

• There is no rotation with this map.

Now that all the required information is collected, let's make this map georeferenced using MAPublisher.

Georeferencing a map using MAPublisher

1. Open the MAP Views panel (Windows > MAPublisher > MAP Views) or click the MAP Views button in the MAPublisher Tool bar.
   
   
2. From the MAP Views panel option menu, click "New MAPView...".
   
   
   The MAP View Editor dialog box opens.
   
   
   
3. In the MAP View Editor dialog box, enter the collected information from above. Enter an appropriate MAP View name. The collected scale value is 1:7,000. Enter 7000 in the scale box. There is no rotation angle value with this map, so leave it as zero.
   
   
   
4. The collected coordinate system for this map is NAD 83 UTM Zone 17 N. The source coordinate system for this map is indicated as [No Coordinate System Specified]. Click the Specify button. It will open the Specify Coordinate System dialog box. Navigate to Projected > UTM > NAD83, then select NAD 83 / UTM zone 17N and choose it from the list.
   
   
   Click OK and the selected coordinate system "NAD83 / UTM zone 17N" will be indicated as the source coordinate system in the MAPView Editor window.
   
   
   Click OK to apply the settings specified in the MAP View Editor dialog box.
   
   
5. In the MAP Views panel, the new MAP View "my map" has been created.
   
   
6. The last piece of the information is very important because we will make a connection between the Adobe Illustrator document and the real world by specifying the coordinate values from both. The MAP Anchor information was collected previously.
   
   From the MAP Views panel options menu, click Specify Anchors.
   
   
7. It is important to confirm what the input cooridnate system is for the real world coordinates that were collected. In this case, they were collected using Google Earth in latitude and longitude values which are in the WGS84 geodetic system. We will specify the input coordinate system as WGS84, not NAD83 (1986).
   
   
   Click the Select button. It will open the Select corodinate system dialog box. Navigate to Coordinate System > Geodetic > World then choose WGS84 from the list on the right side of the dialog box and click OK.
   
   
   Once the WGS84 geodetic coordinate system is specified, it is indicated in the Specify Anchor dialog box.
   
   
   
8. Finally, enter the Map Anchor (real world coordinates) and Page Anchor (document XY) values and click OK.
   
   
   Now the MAPView has the complete information for the georeferencing. The final step here is to bring all the non-map layers to the MAPView we have just created.
   
   
9. In my Adobe Illustrator layers, I organized objects into categories such as water, building and traced roads. To move them from a non-MAP Layer to a MAP Layer, simply click and drag each layer to the "my map" MAP View. Select an appropriate data type for each of the layers when prompted.
   

The Adobe Illustrator document now has the appropriate georeference information and each of the layers now becomes a MAP Layer. From this point, you can add attribute information to MAP Layers, continue to edit features, import new GIS data layers, export MAP Layers to popular GIS formats or convert the map to a geospatial PDF to use it with PDF Maps app for iPhone, iPad, and iPod.