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Google Earth News & Map Data Sources
I’ve been using Google Earth version 5.2.1.1329 (beta) for some time and I find the measurement tab of the path properties dialog very useful. Another very handy feature appears when you right click on a path, the Show Elevation Profile option creates a nice interactive elevation chart.
I stumbled upon a good resource for free online historical maps the other day, Maps ETC from the University of South Florida. In addition to the nice maps they also provide some good basic tutorial videos for Google Earth.
While I was updating some of my Blackstone Valley places files I discovered the Map of all coordinates from Google link on a Wikipedia National Register of Historic Places list article. Clicking the link plots all the sites in Google Maps, but if you click the show link over to the right you get more mapping options. One of the options, Export all coordinates as KML, lets you load the place locations directly into Google Earth.
I decided to load up all the Wikipedia data for Massachusetts and Rhode Island, wow, there are a lot of sites. So I made a version limiting the places to those that fall within the boundary of the Blackstone River Valley National Heritage Corridor.
Most of the sites are not positioned precisely so, I’m tweaking the positions as I work on exploring the BRVNHC. During a recent editing session I found that the National Register of Historic Places provides Google Earth files with some locations updated with more accurate TeleAtlas data. Loading these files along with my my custom file helps in locating the historic sites.
One feature I’m editing into the files I have not found a way to do through GE itself. This is setting the placemark style variations for normal versus highlighted. I’ve set the style so that normally there is no label but when you point to the placemark the label appears and the icon grows. You get this effect by setting up the style block like this:
<StyleMap id="msn_star">
<Pair>
<key>normal</key>
<styleUrl>#sn_star</styleUrl>
</Pair>
<Pair>
<key>highlight</key>
<styleUrl>#sh_star</styleUrl>
</Pair>
</StyleMap>
<Style id="sn_star">
<IconStyle>
<Icon>
<href>http://maps.google.com/mapfiles/kml/shapes/star.png</href>
</Icon>
</IconStyle>
<LabelStyle>
<scale>0</scale>
</LabelStyle>
</Style>
<Style id="sh_star">
<IconStyle>
<scale>1.2</scale>
<Icon>
<href>http://maps.google.com/mapfiles/kml/shapes/star.png</href>
</Icon>
</IconStyle>
</Style>
With no scale parameter specified for an IconStyle the default value is 1, and with no LabelStyle parameter the label scale defaults to 1.
Site Updates
I’ve posted some major updates to the Blackstone River section of my web site. On the Google Earth page I’ve updated the National Park Service tours file and added a file with the 1913 map of the Hopedale Parklands as an overlay in GE. The visitor tips page has a new section covering the few minor natural hazards in the valley (insects, plants, animals).
I wrote an extensive article on the George Washington Presidential Trail which runs through the center of the valley. The article describes the trail and also tries to sort the legends into facts and myths based on historical and geographic research.
The tours file mentioned above was updated based on completing seven of the walking tours this year. The seven tours I took were Arnold Mills, Blackstone Canal, Grafton, Hopedale, Mendon, Upton and Whitinsville. The tours page has been updated with links to the photos I took on these tours. I’ve completed writing reviews for the Mendon and Hopedale tours. In addition to reviewing the tours I also used my history and geography geek skills to research and correct misleading and questionable information from the tours. While taking these tours I shot some new good photos of plants and animals I encountered, they are in the plants and animal sections of my web photo album.
Google Earth Tips
I’ve been using Google Earth (GE) a lot recently for my amateur cartography addiction (it’s been a problem for over 40 years, GE is like crack to me ;-)). In the process I’ve hit upon a couple of tips that don’t seem to be widely mentioned. The first tip is a way to get the length of a path or a polygon perimeter. All you need to do is [Update for GE 5.2]copy the object to the clipboard, paste it into this Google Earth Tool and, click calculate look on the Measurements tab of the objects Properties dialog
The second tip is a bit more complicated it’s how to change a polygon into a path. I created an area boundary as an unfilled polygon which seemed the right way to go. Later I discovered that a polygon blocks all the paths under its area from being clickable for the pop-up information balloons. So I wanted to change the polygon to a path so that the other paths within the boundary area still had their pop-ups. Searching around there where quite a few people who had accidentally created polygons while making a path and no solutions were given. A feature of GE is that if you move the end point of a path near to the start point, it snaps to the start point and becomes a polygon automatically. If that’s not what you wanted and you don’t notice before hitting “OK” you lose your path and there is no option in GE to undo it.
I figured that since GE files are simply XML you should be able to edit the XML to change a polygon to a path so I tried it and it works. All you need to do is right click the polygon and choose “Save Place As”. Change the “Save as type:” to “KML (*.kml)” give it a name and save it. Now open the file in a plain text editor, my current favorite is Notepad++. Simply change the <Polygon> tags to <LineString> tags and remove the <outerBoundaryIs> and <LinearRing tags>. After I had spent a fair bit of time testing out this solution I found the same solution in a Google Groups search. Lesson here for me, don’t skimp on the searches, always include groups and blogs if you don’t find a web search answer.
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