This page explains the map systems on the TowerBells Website, answering the following questions about them:
The heading pane provides only simple identification of the site represented, while a pane down the right side of the map provides some help on using it. If the visitor knows more than we do about where the map pin ought to be located, then instructions in that pane tell how to determine and report a corrected location so that we can improve the map for future visitors.
The info window for the map pin displays the latitude and longitude of that site, which should be the same as shown in the Location paragraph of the site data page from which the map was called (though Google sometimes does strange things to those numbers). That info window also shows how accurate we believe the location to be, and offers links to Google Directions for travel to or from that place.
All site locator maps are independent of each other.
If you resize the browser window horizontally,
the map pane resizes automatically.
But if you resize the browser window vertically, the map pane does not resize;
instead, the brower introduces either a scroll bar or blank space.
We put a tiny line of text below the bottom of the map to remind the visitor that
the necessary workaround is to reload the page after the window has been resized.
(Google must know how to avoid this, since their own maps don't behave this way,
but they won't acknowledge the secret of how to do it.)
The heading pane includes buttons that provide a variety of options. Some offer further customization, while one gives immediate access to the regional map help page (as a popup window). A dropdown menu makes it easy to find a particular site on the map.
The info window for any map pin provides a brief description of what that pin represents, plus one or two links for further action (also explained on the regional map help page).
Regional locator maps are organized into sets (see below).
Both panes of the map resize automatically if you resize the browser window.
The regional locator maps are organized into six independent sets, as follows:
Accuracy has to do with how precisely you know something,
while precision has to do with how well you can specify what you know.
For a location of the surface of the Earth, measured in decimal degrees of latitude
and longitude, this is roughly as follows:
|Whole degree||9.||+/- 30 nautical miles
+/- 55.56 kilometers
|0.1 degree||9.8||+/- 3 nautical miles
+/- 5.56 kilometers
|0.01 degree||9.87||+/- 0.3 nautical miles
+/- 556 meters
|0.001 degree||9.876||+/- 0.03 nautical miles
+/- 55.6 meters
+/- 180 feet
|0.0001 degree||9.8765||+/- 0.003 nautical miles
+/- 5.56 meters
+/- 18 feet
|0.00001 degree||9.87654||+/- 0.0003 nautical miles
+/- 0.556 meters
+/- 1.8 feet
Generally, we use five decimal places when we are confident of placing a map pin on the part of a building or structure that contains the bells, four places when we know only the property, three places when we know only the town, and two places when we know only the country. Someimes we use one more decimal place than is strictly justifiable, simply to place a map pin nicely.
If you've read this far, you might as well read the rest!
Here's a bit of history: When the author began collecting carillon information, around 1960, all that was needed to identify a carillon on an index card was the city, state and institution name. When computerization of the collected information was begun, in the 1970s, it made sense to include the latitude and longitude of the city, as found in printed gazetteers of the day; those values were specified in degrees and minutes. After the software was converted to run on a personal computer, in the late 1980s, a database of geographic boundaries was acquired, on a set of floppy disks. But while the existing city locations would have worked well with this geographic database, the time constraints of earning a living and raising a family did not permit development of a mapping system adequate to utilize it in combination with the author's data. In the late 1990s, when the first version of a Website for the GCNA offered the opportunity to publish the author's data online (see the Website history), it was quickly discovered that there existed free online mapping services that could serve this need. However, proper placement of sites that were accurately known required more precision than was available using just degrees and minutes, so we began stating GPS coordinates as part of the Location section of site data pages. (For the complex history of actually utilizing that information, see our Map Service History.) Now we also include GPS coordinates in the descriptions of independent great bells (when we can). Continue with the answer about locarion accuracy, above.
This page was created 2019/05/11 and last revised 2019/05/13.
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