OpenHistoricalMap/HowToMapBoundaries

Introduction

This is a guide on how to map boundaries in OpenHistoricalMap. The best boundary mapping tool is JOSM, and this guide will assume that's what you're using.

Setting up JOSM

Read this page on how to install JOSM and set it up to use OpenHistoricalMap. It is best to setup most of the plugins and tagging presets listed on that page as well, such as the Tagging Preset to show start_date / end_date in list views, for the selection panel, the relations panel, and the relations editor.

Map Paint styles

JOSM image of Hong Kong

In View ‣ Map Paint Styles set the style to "Admin Boundaries". The yellow dotted lines are ways that have unclosed relations and the pink area is the area of the selected relation. In this example you can see the selected way is not closed and you can see where it’s broken.

Downloading data

Using the Overpass api in JOSM you can query for objects. I usually query for nwr["type"="boundary"]; in the area I’m working on. Sometimes there is too much data so I just query for nwr["admin_level"="2"];. But sometimes, if you’re specifically only working on one thing then you can also download all members of a chronology with this query. relation(id:2747251); relation(r);.

Filtering

Filters in JOSM

I usually have at least two filters in the filter panel that I toggle as needed.

1. type:node with this filter on it hides all nodes which makes it easy to select ways without accidentally clicking or drag selecting nodes.
2. id:0 with this filter you can see which ways are all new.

Splitting ways

Before splitting ways, always download the associated relations so that you don’t break them.

Click on the way you want to split, then File ‣ Download parent ways/relations (Ctrl+Alt+D)

Copy relations from one way to another way

Install utilsplugin then copy the way that you want to get the relations from and select the target way, go to More Tools ‣ Paste Relations

Buffering ways

1. Select the way you want to buffer. Then (Shift+P) or Mode ‣ Parallel and just start dragging the line to the side. In the footer you can see what distance it’s been dragged.
2. The other option is to use QGIS to create buffers

Uploading your edits

Before uploading, search your relations for id:0, edit the relation, go to Parent Relations tab, download the parent chronology or create one if it doesn't exist. Then add your new relations to the chronology.

Often edits are too large and get messed up when the upload fails. In the Upload Panel in Settings, set the upload strategy to around 30 objects per request or 15 if there are any large empires in your edit list, such as the British or Spanish empires.

Guidelines

Mapping Coastal Boundaries

Coastal boundaries are mapped at 3nm from the coastlines and 3.2nm (unless the countries' laws specifically state a distance) for large countries and empires. This is supposed to reduce the amount of ways in large empire relations, and eliminate the need to split large relations when working with smaller states.

Read more at the Maritime Boundaries page