Map Systems
This page explains the map systems on the TowerBells Website,
answering the following questions about them:
The answers appear below, in the same order as those questions.
What kinds of maps are there?
There are two kinds of maps on this Website, as follows:
- A site locator map is a map page that shows just where a particular site
(a single tower bell instrument or independent great bell) is located,
as best we know it.
Such a map is always called from a site data page --
the page that describes that particular instrument --
or from a list of great bells.
- A regional locator map is a map page that shows the locations
of multiple sites in a particular geographic region.
Such a map can be called from almost anywhere
(though it's never called from a site data page).
(We cannot show all of the sites in the world at once, because there are so many
that the response time for drawing the map would be much too long
to be visitor-friendly.
Besides, it would be much too cluttered to be useful.
However, in some major regions you can combine adjacent sub-regions together
if you wish.)
Why aren't maps embedded in the pages to which they are related?
There are three reasons for this:
- Embedding a map in a page would make that page load more slowly.
- Letting a map occupy an entire browser window permits you to see
a much larger area at once.
- That also makes it much easier to provide the special features (customization)
that distinguish our maps from others.
Which mapping services are available?
For site locator maps, there are up to six worldwide mapping services --
Google Maps, Apple Maps, Bing Maps, HereWeGo, MapQuest and OpenStreetMap.
Two regional mapping services -- StreetMap and Kraks Kort --
are also available in their respective regions (the UK and Scandinavia).
For older site data pages (those last updated before mid-June 2020),
only two of those mapping service (Google Maps and MapQuest) are available worldwide,
and the choice is available on the site data page itself.
For newer site data pages, when you first click a site locator map link
you will be taken to a Mapping Service Selector page;
your selection(s) there will be remembered for the duration of your session
using cookies.
You will also have the option to remember them for the future
if you are on a private computer.
If you want to make that choice now, you can visit the
Mapping Service Selector page directly,
though you choice will only be effective on the newer site data pages.
As of the last update to this page, that is somewhat more than half
of the thousands of such pages here.
For regional locator maps, only the Google Maps service is used.
That is because such a map requires a much higher degree of customization,
which happens to be available only through the Google Maps API
(application programming interface).
Besides, the content and appearance of the underlying map are less important
in this case than the nature of the customized information being presented.
What are the characteristics of each kind of map?
The answer presented here applies only to the most highly customized maps--those
based on Google Maps.
See our Map Service Features page
for details of the various site locator map services.
The common characteristics of both kinds of map
(site locator & regional locator) are as follows:
- Both kinds of map are built with a customization of Google Maps.
(For the technically curious, this customization involves use of
Google's Application Programming Interface (API) for Maps,
driven by Javascript routines that we wrote,
which run in the Web browser on your computer.)
- Both kinds of map have a small heading pane across the top to provide
identification of just what is being mapped.
The majority of the browser window is occupied by a map pane,
the background of which is supplied by Google Maps.
- Both kinds of map use colored map-tack icons, or map pins,
to mark locations that we have specified.
Clicking any map pin opens a small "info window" displaying some information
about whatever is of interest at that location (a site, a cluster of sites,
or a region).
- Both kinds of map are initially centered and zoomed to suit what is known
about the site or region being depicted, assuming that the visitor has a
computer display of ordinary size.
(We have made no effort to tailor our pages to display well
on the small screens of smartphones and tablet computers, though some friends
have reported that they can manage quite well on such devices.)
- On both kinds of map, all of the mapping service's usual map controls
(pan, zoom, etc.) are available, and work as expected.
The distinguishing characteristics of the two kinds of map are as follows:
- A site locator map uses the standard version of a map service's
overhead photography (if available), zoomed in as close as practical -- preferably to show
just which part of a building or other structure contains the particular
instrument or independent great bell to which it is related.
However, sometimes it only points to somewhere on the property, or in the town,
or in the worst case just the country where the site is located.
Regardless of the type of instrument,
the standard map pin for that service is used as a marker for the location.
Additional features are available on the Google Maps customization:
- A heading pane above the map provides a 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.
-
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.)
All site locator maps are independent of each other.
Each can be accessed only from the site data page for that particular site.
- A regional locator map uses a customized version of Google Maps road map
to show the locations of multiple sites within a particular region --
the world, or a continent, or a country, or a North American state or province.
It uses a variety of map pins to show different kinds of sites,
or clusters of sites,
as well as adjacent or subordinate regions to which the map can be shifted.
(For details of the different map pins used,
see the regional map help page.)
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.
Both panes of the map resize automatically if you resize the browser window.
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 the answer to the next question).
Within a set, it is possible to navigate directly to sub-regions, adjacent regions
or the parent region.
When there are adjacent regions, it is often possible to add an adjacent region
to the current map instead of switching to it.
How are the regional locator maps organized?
The regional locator maps are organized into seven independent sets, as follows:
- A world map set including all instruments and independent great bells.
This set begins with a world map that contains five continental sub-regions;
it's here.
- A world map set including only traditional carillons.
This set begins with a world map that contains five continental sub-regions;
it's here.
- A world map set including only rings outside of the British Isles.
This set begins with a world map that contains two continental sub-regions
and two country sub-regions;
it's here.
- A world map set including only great bells, whether independent or
contained in carillons or other kinds of instruments.
This set begins with a world map that contains five continental sub-regions;
it's here.
- A world map including only zvons. It has no sub-regions;
it's here.
- A world map set including only tubular tower chimes outside of the British Isles.
This set has a sub-region for North America, but shows all other sites directly;
it's here.
- A North American map including only non-traditional carillons.
It has no sub-regions;
it's here.
Regional locator map sets can be entered directly at any sub-region.
This is convenient for connecting them to various index pages
without losing access to the entire set.
How are varying levels of location accuracy handled?
Accuracy has to do with how well 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:
| Precision |
Example |
Maximum error
(accuracy) |
| Whole degree |
9. |
+/- 30 nautical miles
+/- 55.56 kilometers |
0.1 degree
(6 arc minutes) |
9.8 |
+/- 3 nautical miles
+/- 5.56 kilometers |
0.01 degree
(0.6 arc minutes = 36 arc seconds) |
9.87 |
+/- 0.3 nautical miles
+/- 556 meters |
0.001 degree
(3.6 arc seconds) |
9.876 |
+/- 0.03 nautical miles
+/- 55.6 meters
+/- 180 feet |
0.0001 degree
(0.36 arc seconds) |
9.8765 |
+/- 0.003 nautical miles
+/- 5.56 meters
+/- 18 feet |
0.00001 degree
(0.036 arc seconds) |
9.87654 |
+/- 0.0003 nautical miles
+/- 0.556 meters
+/- 1.8 feet |
The accuracy specified in the last column applies strictly to measurements of latitude.
For longitude, it is correct only at the equator; the maximum error for a given precision
shrinks progressively as one moves toward the poles, according to the cosine of the latitude.
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 on the overhead photography of Google Maps.
Answers to questions you didn't think to ask?
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 a handwritten or typed 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 in the USA 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 location accuracy, above.
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This page was created 2019/05/11 and last revised 2023/12/30.
Please send comments or questions about this page to
csz_stl@swbell.net.