Thursday, 11 December 2014

City Stripping : building historical road layouts from todays data

Buenos Aires - Plano de Basch (1895)
Street map of Buenos Aires 1895 (plano de Basch)
Source: Wikimedia Commons

For at least one year I have been thinking about the best way to create vector streetmaps for different historical periods for the same city. The basic principle is simple: take the existing street layout and remove what is new! Essentially, this presumes that any current vector data will be more precise than digitising vectors from old maps.

I have even given the process a name: "City Stripping", but in practice my attempts so far have been less successful than I hoped. I think that  I kept too much existing OpenStreetMap data in my first attempts, because in practice I found it easier to re-trace the old data (as here for Tartu/Dorpat).

State of the Map 2014 in Buenos Aires provided another opportunity to try this out. Fortunately a small number of historical maps were available on Wikimedia Commons. I chose two:

Thursday, 30 October 2014

War Memorials: revisiting an OpenStreetMap Project of the Week

Great Gable from Broad Crag col - - 768103
Great Gable, a mountain in the English Lake District.
The summit and around 1200 ha of the surrounding area are dedicated as a war memorial.

Four years ago I proposed mapping war memorials as the OpenStreetMap Project of the Week. It ran in early November 2010 to coincide with the anniversary of Armistice Day, when several countries honour their war dead. At the time I was intrigued at how this particular topic resonated with mappers.

I was gratified that both Peter Reed and Chris Hill felt engaged by the idea. Richard Weait, co-ordinator of Project of the Week, wrote a very interesting post about the poem "In Flanders Field" which was written by a Canadian.

Tuesday, 28 October 2014

Strava & OpenStreetMap GPS traces: a quick comparison

Strava introduced their heatmaps and their Strava Slide tool at the Washington DC conference of the OSM US community SotM-US in the spring. I had a quick look at the time and it seemed interesting, but there was little data in areas which I map.

A question came up recently regarding how accurate the Strava heatmaps are for mapping routes on OpenStreetMap, particularly in wooded areas. This prompted me to have another look at the data.

It happens that I have made a lot of traces across two paths on an open playing field (an area sufficiently unobstructed that it is used periodically for calibrating and testing professional grade GPS equipment). A short distance from these two paths is NCN 6, a heavily used national cycle route. It was therefore very easy to grab some screen grabs of Strava and OSM data:

Jubilee Campus, Nottingham : Strava Heatmap
Strava Cycling Heat Map
(NCN 6 on left, university cycle paths centre & right)

Jubilee Campus, Nottingham : OSM GPS traces
The same area showing traces which have been uploaded to OpenStreetMap
(probably mainly by me)

Tuesday, 7 October 2014

Plantations : woods, forests or something else?

Stand of trees at New Fen - - 636879
Poplars at Lakenheath
CC-BY-SA 2.0   © Copyright Alison Rawson and licensed for reuse under this Creative Commons Licence.
One type of woodland area I have alluded to a couple of times in the past are plantations (see here and here). I've always been frustrated at not having found good illustrations, but in the past couple of weeks I've noted a few which either already have good open images available or I've been able to snap a picture myself.

Plantations run the gamut from small areas to fully-fledged forests. In general what connects them is that the trees are planted in orderly rows, and the plantation has an expected lifetime, after which the trees will be harvested or replanted. Photographs enable some of the variety to be shown. In turn this should highlight the sorts of information we might want to capture by OpenStreetMap tags.

Thursday, 18 September 2014

OpenStreetMap at the UK Open Addresses Sympoosium

I attended the Open Addresses Symposium organised by Jeni Tennison of the Open Data Institute last month. This brought together a host of people and organisations interested in having an open alternative to the Postcode Address File (PAF).

Somewhat foolishly I'd suggested to Harry Wood that I might speak about addresses on OpenStreetMap.

Addresses mapped on OpenStreetMap in Britain
Density of address mapping in (southern) Britain on OpenStreetMap by local authority
(Northern Scotland not shown because little data, full map)
See text on map for full explanation.
I was glad to see that my talk was relatively late on in the day: the audience were unfamiliar and many of them came from large organisations., so I appreciated the chance to get an impression of them.

Tuesday, 2 September 2014

Woodland Cartography

This is an expanded version of my talk at sotm-eu:

I start by seeking inspiration from the many ways in which woods and trees have been shown on maps in the past, and then consider what elements we may want for OSM data, and how we might depict such elements.

Monday, 1 September 2014

Contributing to the Lesotho Mapathon

At the start of August I appeared in the OpenStreetMap stats for users adding most data in a day. This was the first time in ages that I've made enough edits to appear. The reason: I've been contributing this past week to a mapathon to map as much of Lesotho as possible. This has been co-ordinated by Irish OSM contributors, some of whom will travel to Lesotho early next year.

View from Lesotho village (5297237744)
A village in Mokhotlong District.
This is S of the area I have mapped, but looks similar on aerial photos.
Source: Wikimedia Commons.
The co-ordination makes use of the HOT Task Manager: a piece of software which has distant origins in something, long gone, called QualityStreetMap.

I've use the Task Manager fairly rarely, but development over the past year has added one feature which for makes it much easier to use: the creation of a bounding box in the JOSM editor. It is now much simpler to see the area one has undertaken to map. This in turn is important in reducing editing conflicts and redundant work.