Mapping for Stream Waders near Howard County
A map of targeted watersheds to help an ad hoc team of volunteers coordinate monitoring.
Why was this created?
After training, volunteers were organized into teams to sample designated watersheds. The map was created to keep all team members aware of progress in sampling. The team was responsible for the blue watersheds. Red were targeted watersheds but unassigned to any team, so were available if there was extra time available. The blue "push pins" show the locations of samples actually collected. After samples were collected, the team members notified the team leader who updated the map.
How can you use this example?
The strategy used here can generally be used for displaying GIS shape files.
How does it work?
The Maryland Department of Natural Resources provided a map of watersheds selected for sampling this year. Along with other GIS data, the DNR provides a GIS shape file of all watersheds in the state.
Using commercial or open source GIS software, it is possible to extract one or more shapes (in this case, watersheds) from the larger shapefile (in this case all the Maryland watersheds.) Those extracted shapes were then saved as a new shapefile. Most GIS software can also save the shape file as a KML file which is needed for display in Google Maps (or Google Earth). Alternatively, software, such as shp2kml, can be used to convert a shape file into KML. You can display and do some editing of the KML file using Google Earth.
KML is a text format like other XML-based formats. This means that you can carefully edit the KML file to achieve the adjust the display.
For example, it is relatively easy to delete "placemarks," in this example, corresponding to watersheds. Changing icons, colors, etc. requires more understanding of the KML to achieve the desired results.
A combination of modifications in Google Earth and editing of the KML file with notepad was used to modify the KML in this watershed example.
- The Google Maps API documentation is available on the Google web site.