Wednesday, November 14, 2012

Web Maps for Digital Humanties

As I'm currently working with two digital humanities groups on web projects, I have been thinking about easy/free ways to get humanities, particularly historical, resources on the web.  The heavier weight self-hosted option we're using is Omeka, and the lighter weight-cloud hosted option is ArcGIS Online.  Omeka provides the kind of exhibits, metadata, and other functionality often crucial to scholarly digital humanities publications, while ArcGIS is more suited as a secondary product or as a class project -- with a significantly fewer adoption costs.  On Omeka, we're using the Neatline and Neatline Maps plugins, as well as Geoserver.

Here's a good workflow for Omeka/Neatline Maps/Geoserver:
  1. Download or scan a (historical) map image
  2. You will need to use GeoTiff format to work with Neatline Maps. I used ImageMagick to convert your format to TIFF.  We'll worry about georeferencing (the Geo in GeoTIFF) in the next part.  You'll need to use the command line IM tool -- "convert" is a built in Windows system executable, so you'll need to specify the path when you execute from CL, if the IM binary folder is not on your system path.
  3. Now that you have your TIFF, georeference with ArcGIS Explorer Desktop and the Georeferencing Add-In.  Explorer is freely available.  You'll find links to download Explorer and the Georeferencing Add-In, as well as instructions for doing the Georeferencing, here:
  4.  After you've gereferenced and saved your TIFF, import it into your Omeka/Neatline Maps site (Add an Item > Files > "Add New Files" and browse to your TIFF ... "Add Item"
  5. Your image should now be added to Geoserver and is provided back to NL Maps as a WMS.  Though NL Maps is designed to add the reference to the WMS, we identified a bug that prevented this from occurring.  At this time you will need to add the reference directly through the Edit Item dialog in the Web Map Service tab.  You will need to populate the WMS Address and Layers fields in this tab, in this format:
    1. WMS Address: http://HOSTNAME:PORT/geoserver/NAMESPACE/wms
  6. Next you must create a NL Exhibit through the Neatline tab at the top of the Omeka admin interface.  Once you have created the exhibit, you must Edit Query to include the map image.  I found that the easiest way to get the item you want int the query is to Narrow by Specific Fields using the Title field, with the value of the map image title.
  7. Now, when you edit the exhibit, you should see the map image displayed at the proper location.  First, I panned and zoomed to the location of my image.  I immediately changed the opacity of the image via Map Settings > Shape Opacity within the neatline exhibit editing interface.  Next, I fixed the starting point of the map with Layout Editor > Fix starting viewpoint position, within the same inteface.  I saved these changes subsequent to making them, and then refreshed the interface via the browser to see the changes.  
  8. Finally I could view my NL Maps Exhibit through  http://SITEURL/neatline-exhibits/show/NLEXHIBITNAME

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