Embeddable Single-Year OpenHistoricalMap

Single year embed version of OHM default map style

This is a simple embeddable version of the OpenHistoricalMap default map style, with the ability to select and display a single year via URL parameter.

The use case for this would be, for example, to embed map showing a specific place and time in a blog post about that place and time. The map is zoomable and pannable, but doesn't allow changing the year within the interface, such as is possible with the timeslider on openhistoricalmap.org.

The base URL of the embed is https://embed.openhistoricalmap.org/

URL parameters

The URL has typical z/x/y parameters for map zoom and center.

So a parameter like #map=10/43.9367/12.5528 is zoom 10 showing San Marino in Italy, which is at 43.9367/12.5528 in lon,lat format of decimal degrees. See the map.

An embedded map is typically of a different size and aspect ratio from the original and thus must be scaled in order to cover a comparable area. This is accomplished by passing the original map's bounding box in the hash as &bbox=minlon,minlat,maxlon,maxlat. Once the embedded map gets its initial framing from the bbox the normal hash mechanism takes over. The San Marino example could be bounded by appending &bbox=12.321338653564453,43.86782687726672,12.58037567138672,44.008373185063874 to the URL. See this map.

Dates

Without a date parameter, the map shows everything in the OHM tiles for which there is a style specified.

OHM-specific parameters:

• date is a valid YYYY, YYYY-MM, or YYYY-MM-DD date, but we allow the year to be a variable number of digits or negative, unlike ISO 8601-1. So here is San Marino in the year 1500 #map=10/43.9367/12.5528&date=1500. See this map.
• layer is one of O, W, or J. This allows the selection of alternative OHM-compatible styles currently offered on openhistoricalmap.org. The default OHM style is O. The Japanese Scroll style is J. The Woodblock style is W. Here is a query string for San Marino in 1500 in the Woodblock style: #map=10/43.9367/12.5528&date=1500&layer=W. See this map

Embedding

Simply use code like this to embed:

    <iframe src="https://embed.openhistoricalmap.org/#map=10/43.9367/12.5528&date=1500&layer=O" height="500" width="100%" title="OpenHistoricalMap: San Marino in 1500"></iframe> 

Here's an example iFrame.

For development

Start a webserver in this directory, e.g., http-server. Use the resulting base url, e.g., http://localhost:8082/ as ohm-website's embed_server_url in config/settings.local.yml.