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Geocode MoEML Locations

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Basics of Geographic Information System (GIS) Locations

Any place on the surface of the earth can be located in terms of three coordinates: latitude, longitude, and elevation (height above sea level). In most of our work, we are concerned with only the first two, latitude and longitude, because we don’t (currently) envisage any rendering or data processing that would make use of elevation.
Traditionally, latitude and longitude were expressed in degrees, like this:
51°30'49.25"N
 0° 5'58.42"W
These are the coordinates of St. Paul’s Cathedral. Notice that the longitude coordinate starts with zero. St. Paul’s is very close to Greenwich, through which the zero line of longitude, the prime meridian, runs.
In modern GIS systems, latitude and longitude are expressed in decimal numbers, which look like this:
-0.098369
51.513557
You can see that these are the same basic numbers—latitude measured as distance north or south from the equator, longitude measured as distance east or west from the prime meridian—but they’re expressed in a form that enables computers to do math with them more easily. They’re also reversed: longitude comes before latitude in most modern computing contexts.
Coordinates like this are usually comma-separated, like this:
-0.098369,51.513557
and if elevation is also included, it comes last, like this:
-0.098369,51.513557,0
Our geo-location work falls into two phases: discovering the actual location, and then generating coordinates for that location the form of a GeoJSON geometry.

Resources for Finding Geo-coordinates

At the moment, historical geo-coordinates are not nearly as readily available as modern-day geo-coordinates. Generally speaking, those who wish to work with historical geographic data are expected to infer geo-coordinates from their own research. We can infer the geo-coordinates of early modern locations from the geo-coordinates of modern administrative boundaries, sites, and structures.
There were three cataclysmic events that changed the face of London:
  1. The Great Fire of London (1666)
  2. The Victorian expansion of London (19th century)
  3. The Blitz (1940-1941)
Despite these events, London’s street layout, administrative boundaries, and property lines have been remarkably stable. Changes to administrative boundaries are well documented, which means we can work backwards from modern boundary maps if necessary. Sometimes building plans and street surveys survive (such as Ralph Treswell’s property surveys; see Schofield). Archaeological finds in London are geo-referenced, which gives us corroborating evidence for some locations (especially the footprint of structures now lost, such as theatres).
A good rule of thumb is to start with the earliest map and work forward through time.
The following is a list of resources that you can use to research location geo-coordinates:
  • Agas Map
    Always start with the Agas Map! Civitas Londinum is a bird’s-eye view of London first printed from woodblocks in about 1561. If your place is depicted on Agas, you will be able to greatly narrow-down the place’s location in modern London.
  • Carlin & Belcher’s 1520 Map
    The 1520 Tudor map depicts London before the 1536 dissolution of the monastareries. It was reconstructed by historians and archaeologists and covers a large geographical area, including part of Southwark.
  • London Archaeological Archive and Research Centre Online Catalogue (LAARC)
    LAARC is a database of site records from archaeological digs in London. Each site record has been assigned geo-coordinates that correspond with the point where historical evidence of the location was discovered by archaeologists. Site records are searchable via the website’s home page. Note that even though it is possible to search by street name, LAARC provides point-based geo-coordinates for archaeological finds under modern streets, not line-based geo-coordinates for the early modern streets themselves. LAARC usefully lists all the scholarly articles and monographs about a particular dig, from which we can derive further information.
  • Shakespearean London Theatres (ShaLT)
    ShaLT maps all the early modern London theatres and provides resources, maps, and suggested walking tours. Each location (exclusively playhouses and related locations) has been assigned geo-coordinates that define where the location existed in Shakespeare’s London (defined as 1570s to 1642). Locations are indexed on the locations page. We have now added all of the ShaLT coordinates to our playhouse location files.
  • GeoNames
    GeoNames is a global database of geo-coordinates that contains over 100 modern-day locations in the City of London. Locations are searchable by toponym at the website’s home page and visually via the website’s map widget. Note that GeoNames is a modern-day gazetteer. Geo-coordinates for a modern-day location may not perfectly correspond with the location’s early modern predecessor.
  • Locating London’s Past
    Locating London’s Past is a GIS interface that links various seventeenth and eighteenth-century datasets with a georectified version of John Rocque’s Survey of London, Westminster, and Southwark (Rocque). Geo-coordinates are not visible to the user. However, Tim Hitchock (one of the project directors) has kindly supplied MoEML with the project’s .KMZ files that contain geo-coordinates for streets and parishes. MoEML team members may ask Janelle Jenstad for access to these files, which you can open and search in Oxygen.

Manually Find Geo-coordinates

In many cases, you will be unable to find geo-coordinates for a location using the resources listed in the previous section. When this happens, you must use your own research on the location to infer its location on a modern-day online map of London. The following sections describe how to extract geo-coordinates manually for user-selected points, lines, and polygons by first searching for the location using the Vertexer—a mapping markup tool developed by Greg Newton at HCMC. You may also use the OpenStreetMap Nominatim database, and if you need to generate complex geometries such as MultiLineStrings (for broken streets) or MultiPolygons (for locations which have multiple unconnected shapes) the HCMC World Map for Drawing provides a richer drawing interface. Both the Vertexer and the HCMC map provide exactly the TEI code that you need to insert into the location file.

Introduction to OpenStreetMap Nominatim

The open-source OpenStreetMap organization maintains a huge database of locations called Nominatim, and you can search it at using the Vertexer or OpenStreetMap.org. Note that historical locations are not very well represented, and the current coordinates of historical places may not accurately represent their original location. Nevertheless, this is a good starting point when it comes to finding the modern coordinates for a historical place. When you search on the Vertexer, a drop-down list of potential locations will appear. If one of them looks correct, you can place it on the map by clicking on the point icon to the left. If there is already a full geometry for the place in Nominatem, you can click instead on the second icon.
If the place you have found is correct, your next job is to either confirm that existing geometries are correct and acceptable, or draw a new geometry. Often, the Nominatem database will include only a point location, but we would prefer something more precise, so you may wish to draw a polygon instead. To draw a Point, LineString or Polygon, click on the appropriate icon on the right, and start clicking on the map to add points. When you have finished, either click back on the first position (for a Polygon), or double-click the last position (for a LineString).
If you are happy with your shape, click on the Export button (second icon on the right), and a popup box will show the TEI code you need for the location file. Note that you need to click on the TEI option to see the right code.

Placing the Geometry Information Into the TEI File

Modern geographical information is stored right at the beginning of the <body> of a TEI location file. There you will find a <div> element with @type="placeInfo", like this:
<div type="placeInfo" xml:id="SOME50_placeInfo">
  <head>Something Lane</head>
  <listPlace>
    <place>
      <placeName>Something Lane</placeName>
      <location type="GeoJSON" source="mol:VERT3" resp="mol:TAKE1" when="2016-05-06"><geo resp="mol:HOLM3"> "geometry": { "type": "LineString", "coordinates": [[-0.087802,51.514622], [-0.08751,51.514249], [-0.087314,51.513917]] } </geo></location>
    </place>
  </listPlace>
</div>
The <location> element must have @type="GeoJSON". You can also add source info (here the Vertexer, VERT3, is the source), a resp attribute pointing to yourself, and dating info if appropriate. Then paste the <geo> element from the Vertexer inside the <location> element.
That should be all you need to do. Make a note to yourself to check the resulting location page on the MoEML Jenkins site when the next build has completed to see if your map appear as you expect.

Documentation, Sources and Certainty

When you add a new GeoJSON location, you should document your work by:
  • Adding a @resp attribute to the <location> element, pointing to yourself
  • Adding a <respStmt> to the header, with <resp>/@ref pointing to "molresp:gis"
  • Adding a <change> element to the <revisionDesc>
You should also cite one or more sources for the information that allowed you to discover the coordinates, by adding @source to the <location> element. This may be as simple as citing OpenStreetMaps (@source="mol:OSMD1"), or perhaps pointing to a chapter or section of Stow which provided the information. You can add multiple pointers inside @source.
It is not uncommon for there to be a degree of uncertainty about a location. There are two types of uncertainty. You may be unsure about the precise coordinates of a place because the surrounding cityscape has changed significantly. In that case, you would add @cert="medium" or @cert="low" to the <geo> element itself. On the other hand, there may be some confusion about the broader location; if there are two Smith Streets, and it is not clear which one is the right one, then you would have to pick the most likely one, but you might add @cert="medium" to the <location> element to specify that the uncertainty relates to the general location rather than the coordinates.

Introduction to HCMC World Map for Drawing

HCMC has a World Map for Drawing based on the same OpenStreetMap data. This map allows you to create points, lines or polygons representing a location, and will then generate TEI code which you can then embed directly into the location file you are working on.
When you first go to the site, you will see that the map zooms in on the UVic campus, but if you click on London, UK and then select Agas London, the map will move over the London and provide you with a bounding box around the rough area covered by the Agas Map.
Now zoom in to locate the place you found through Nominatim or some other resource, and you’re ready to start drawing. This map makes it possible to create an additional geometry type, the GeometryCollection, which is what you need if your location includes a mixture of two or more different types of base geometry (such as a LineString and a Polygon).

References

Cite this page

MLA citation

Holmes, Martin D., Tye Landels-Gruenewald, Martin D. Holmes, and Janelle Jenstad. Geocode MoEML Locations. The Map of Early Modern London, Edition 6.6, edited by Janelle Jenstad, U of Victoria, 30 Jun. 2021, mapoflondon.uvic.ca/edition/6.6/geo.htm.

Chicago citation

Holmes, Martin D., Tye Landels-Gruenewald, Martin D. Holmes, and Janelle Jenstad. Geocode MoEML Locations. The Map of Early Modern London, Edition 6.6. Ed. Janelle Jenstad. Victoria: University of Victoria. Accessed June 30, 2021. mapoflondon.uvic.ca/edition/6.6/geo.htm.

APA citation

Holmes, M. D., Landels-Gruenewald, T., Holmes, M. D., & Jenstad, J. 2021. Geocode MoEML Locations. In J. Jenstad (Ed), The Map of Early Modern London (Edition 6.6). Victoria: University of Victoria. Retrieved from https://mapoflondon.uvic.ca/editions/6.6/geo.htm.

RIS file (for RefMan, RefWorks, EndNote etc.)

Provider: University of Victoria
Database: The Map of Early Modern London
Content: text/plain; charset="utf-8"

TY  - ELEC
A1  - Holmes, Martin
A1  - Landels-Gruenewald, Tye
A1  - Holmes, Martin
A1  - Jenstad, Janelle
ED  - Jenstad, Janelle
T1  - Geocode MoEML Locations
T2  - The Map of Early Modern London
ET  - 6.6
PY  - 2021
DA  - 2021/06/30
CY  - Victoria
PB  - University of Victoria
LA  - English
UR  - https://mapoflondon.uvic.ca/edition/6.6/geo.htm
UR  - https://mapoflondon.uvic.ca/edition/6.6/xml/standalone/geo.xml
ER  -

TEI citation

<bibl type="mla"><author><name ref="#HOLM3"><surname>Holmes</surname>, <forename>Martin</forename> <forename>D.</forename></name></author>, <author><name ref="#LAND2"><forename>Tye</forename> <surname>Landels-Gruenewald</surname></name></author>, <author><name ref="#HOLM3"><forename>Martin</forename> <forename>D.</forename> <surname>Holmes</surname></name></author>, and <author><name ref="#JENS1"><forename>Janelle</forename> <surname>Jenstad</surname></name></author>. <title level="a">Geocode MoEML Locations</title>. <title level="m">The Map of Early Modern London</title>, Edition <edition>6.6</edition>, edited by <editor><name ref="#JENS1"><forename>Janelle</forename> <surname>Jenstad</surname></name></editor>, <publisher>U of Victoria</publisher>, <date when="2021-06-30">30 Jun. 2021</date>, <ref target="https://mapoflondon.uvic.ca/edition/6.6/geo.htm">mapoflondon.uvic.ca/edition/6.6/geo.htm</ref>.</bibl>

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