Workflow

The figure below shows a typical workflow used in this project for assembling a desktop GIS project using QGIS and uDig, which were introduced in the Desktop Tools subsection.  It includes the special workaround required to process data files obtained from the Michigan State Center for Geographic Information before it can be handled successfully by QGIS.


Much of the effort lies in assembling or creating the necessary basemap and overlay layers for the map.  Aerial photographs for overlaying data layers can be obtained (for purchase) from Antrim and Grand Traverse Counties.  Alternatively, the 2010National Agricultural Imagery Program (NAIP) 1-meter resolution imagery can be loaded into QGIS from a WMS server operated by the US Geological Survey (USGS) ("getcapabilities" link here).  Older aerial photographs can be loaded onto QGIS from other USGS WMS servers.

For this project, participants are encouraged to create GIS maps using the State Plane Coordinate System as the map projection.  For the project area, we are in the Michigan Central zone, NAD 83 datum (FIPS2112 and EPSG:2252).  As township users are expected to exchange data with their county GIS staff from time to time, standardizing on State Plane would greatly facilitate the interchange of vector and raster files.  County GIS sections are probably the best source of current parcel, road, and other infrastructure layers.

Another excellent (and free of charge) source is the Michigan Geographic Data Library, maintained by the Michigan (state) Department of Information Technology.  As noted in the previous section, these files come projected into the Michigan GeoRef projection, which QGIS and many other open source software depending on GDAL libraries cannot handle correctly.  (See Project Tutorials section.)

To overcome this obstacle, this project uses the shapefile re-projection capabilities of the uDig package to convert the state-supplied shapefiles from the GeoRef projection to the State Plane Coordinate system (or some other non-GeoRef projection).  Shapefiles and spatial layers in other formats that are not in Michigan GeoRef can be loaded directly into QGIS.

Another source of specialized GIS layers for use in informational maps for townships is the large community of quasi-government and NGOs that use GIS for their own missions.  Examples are the local Conservation Districts, Land Conservancies, the Grand Traverse Watershed Center, and various other organizations like TART Trails, to name a few.

The GIS map created using QGIS is typically saved as a PDF document which is then made available for download from the township website.  The shapefiles and other data layers used in creating the GIS document, along with their styling information, are then carried over into the web mapping step for conversion into a form used by web map applications.

As noted further in the following Web Mapping section of this website, depending on the type of web map to be made, data layers should be converted to KML files, along with styling data.  KML files can then be compressed into zipped KMZ files, and downloadable, stand-along KMZ files can be created.  These KMZ data files can be downloaded by members of the public and viewed on Google Earth – another highly effective means of information and data dissemination.
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