By Jennifer Woodson on Friday, 19 June 2015
Category: Real Life Applications

Using Didger and MapViewer to Build a Site Map

I recently took a trip to Tennessee to attend the 14th annual Bonnaroo Music and Arts Festival. The festival takes place on a 700-acre farm in Manchester, TN. In addition to music and art installations, Bonnaroo has campgrounds organized by pods, a cinema tent, a comedy theater, and more! Upon arrival to the festival, attendees are given a map of the festival site. With stage names that include What Stage, Which Stage, This Tent, That Tent, and The Other Tent, the map is a necessary tool for many attendees! For this post, I used a combination of Didger 5 and MapViewer 8 to recreate the map and export it to KML to display in Google Earth.

To begin, I downloaded the PDF version of Bonnaroo's map (pictured below) from their website.

Map downloaded from Bonnaroo's website.

Next, I used Google Earth to locate some known points to use to georeference the image in Didger. A few of these points are pictured below.

A few reference points used in Google Earth.

I imported the PDF into Didger and calibrated it using the points I retrieved from Google Earth. I quickly realized, though, that this approach was not going to work well for me. While the map I downloaded from Bonnaroo's website is a great and very helpful visualization of the festival site, it is not a very accurate map. That is, it is not properly oriented, has an odd field of view, and is not necessarily drawn to scale. This map is not a great candidate for accurate digitizing. Didger was able to locate the map correctly, but not without great distortion and warping. The warping made it difficult to digitize the areas in their (relatively )true shapes.

Back to the drawing board. I wasn't giving up yet! I decided I wanted to recreate this map, and I was going to do it! This time, I decided I could digitize directly from a Google Earth image. I returned to the area pictured above in Google Earth and added a few more pins for reference points. I also added pins in each corner and noted their coordinates. I took a screenshot, and I was off!

I imported the screenshot into Didger, georeferenced it using the coordinates from the pins in the corners, and began manually digitizing using the Draw commands. When my digitizing was complete, I exported the map to a DXF file in order to continue working in MapViewer.

In MapViewer, I created a base map from the DXF file, and I adjusted some line styles to make some areas stand out. After I edited line widths, I created a legend and then exported to KML. I edited the line styles in MapViewer because Didger does not currently export the line widths to KML. Below is the final map displayed in Google Earth.

Final map, displayed in Google Earth.

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