Half Way at New Street station Birmingham

On 28th April New Street Station got a brand new set of entrances leading to a brand new concourse.

This marks half way in the total transformation of the station

 The old entrances at the eastern end by T K Maxx are now closed and new entrances opened at the western end. If you're approaching by car the new Drop and Go access is from the west,  off Navigation Street. There's also a new short stay car park above the station approached from the Drop and Go access road. Anyone arriving at New Street station now has a totally transformed experience of modernity and light rather than the dingy dim experience of before. Congratulations to Network Rail!

Needless to say we had it surveyed and live to the world by lunchtime on April 28th, some 5 hours after the new configuration opened!

Mysterious objects- No 5 in an occasional series

I was out walking in the Warwickshire countryside last weekend and came across these unusual objects. Each one was numbered and no more than a couple of meters from the next numbered object. I saw two sets of at least 100 of these, and now release they are located in hedgerows or tree-lined field boundaries that HS2 will cut through (if built).

Any ideas?

A fresh new look

To coincide with our brand new State of the Map 2013 website, we are currently exploring a new fresh look for this Mappa Mercia site. Its still early days but all and any feedback is welcome.

You can view the new design (work in progress) by clicking here.

Conference: State of the Map 2013

Many of you will have already heard the great news, but for those who haven't, I am pleased to announce that OpenStreetMap's annual conference will be held in Birmingham, from 6th – 8th September 2013.

The conference, known as State of the Map 2013 (SotM 2013), will see 300 users converge on Birmingham to discuss everything OpenStreetMap. It's been 6 years since the conference was last held in the UK and in that time OpenStreetMap has developed from a project with 10,000 contributors, to one of 1.05 million registered users. To reflect on this huge growth, this years theme is "Change".

Simon Poole, Chairman of the OpenStreetMap Foundation reflects: 

"Change is a constant in OpenStreetMap. Not only does the world around us change and require resurveying all the time, the OpenStreetMap project itself continues to evolve very rapidly in every aspect. The organisation that is returning to the UK with its main public event after 6 years, has grown from a small, fun project, to an undertaking that is competing with multi-billion dollar corporations but still is fun for everybody involved. In that vein I'm looking forward to SOTM in Birmingham and expect that we will all have a great and interesting time."

Being such a big event, we are delighted that we are not alone in organising the conference. In addition to regular Mappa Mercia members, we also have the support of many other OSMers from both inside the UK and around the world. Thank-you for all your input.

For more info see: stateofthemap.org

Exploring OpenStreetMap data

10 March 2013, RobJN

In my December and January blog posts about Maperitive, I discussed how to download OpenStreetMap data. The first method used the “export” feature on the osm.org homepage to download all data within a geographic area, whilst in my second post we used the Overpass XAPI Compatibility Layer to download just those ways (polylines) tagged as gritting routes.

In this post we will explore how to find out more about OpenStreetMap tags and how we can visualise the data online.

OpenSteeetMap Wiki

The OpenStreetMap Wiki is the main documentation portal for OSM. The Map Features page provides an initial list of tags, with links to detailed pages about man tag keys and values (recall that all tags are in the format key=value). For example the tag “highway=footway” has a wiki page all about the key “highway” (see Key:highway), in addition to a page specifically about the “footway” value (see Tag:highway=footway).

Note that the wiki should be considered as a guide only. Not all tags are documented and some tags are marked as “proposals” only. Use the search bar in the top right to help discover related pages.

TagInfo

On both Key and Tag wiki pages, you will often find a box on the right hand side which includes a subsection titled “TagInfo”. This provides stats about how many nodes (points), ways (polylines) and relations (multipolygons) are tagged with that key/tag.

TagInfo stats on the highway=footway wiki page.

TagInfo is a separate website that reports on how tags are actually being used in OSM. By examining the raw data it provides stats about all tags used, not just those with documentation. It also provides information about common tag combinations. So for example we can see here that the the “highway=footway” tag is often combined with tags about the surface and bicycle use. We can also see a static global map of where the highway key is used (see here).

Overpass Turbo

Overpass Turbo is a web based interface for the Overpass API download servers. With turbo you can run any kind of Overpass query and display the results an interactive map. As such it provides greater visualisation of the data than TagInfos basic static map. Be warned however that this should be used for small quantities of data only (that is, infrequently used tags, or if using common tags the interactive map should be well zoomed in). It is also not as simple to use as TagInfo, however each TagInfo page includes a link to turbo (a button with a steering wheel on it) that will pre-populate turbo with the correct query. You just need to zoom in and click "Run".

Overpass Turbo query showing gritting routes in Birmingham

Once you have investigated the OpenStreetMap data you can move on to download it using the Overpass XAPI Compatibility Layer or use the Overpass API queries as shown in the example above.

Rural Mapping

In the West Midlands we’ve been busy with rural mapping. To those of you surprised that there's any countryside in the sprawling industrial conurbation that spreads from Wolverhampton through Birmingham and Solihull into Coventry, we need only quote the motto of Solihull which is Urbs in Rure (Town in Country). You will see that there is a large amount of green belt land that has been jealously guarded by planning authorities. The green belt land provides much needed recreational access for the surrounding population. It will come under increasing pressure from the new relaxations on planning restrictions.

 In a COUNTRYSIDE TRIAL AREA to the eastern end of Solihull and the Western end of Coventry bounded by A45/ Birmingham Road Meriden/ Berkswell Road / Meriden Road / Coventry Road/ Broad Lane/ Eastern Green estates/Allesley Green estates, mappa-mercia mappers have collaborated to produce a rural map  to the most detailed level currently available within OSM 

Guidelines

The guidelines which we evolved by discussion, some concentrating on mapping landuse and others on mapping footpaths, are as follows:
1.All field boundaries are shown using the predominant feature defining it to someone in the field. The most useful are: 
- barrier=hedge 
- barrier=fence 
- waterway=stream 
(NB: if a stream also has hedge one side and fence the other  we only show more 
than one if it is necessary to make situation clearer) 
- highway=service (or higher – only show barrier as well if necessary) 
- boundary between landuse=residential and landuse=farmland (NB – these are not 
so easy to see and therefore adding a barrier as well is desirable, or for “MapQuest Open” type rendering, essential 

2.   Adding the main buildings within a residential area is desirable in order to give as god idea what the area looks like. 
We  have tried to add all houses, and usually all similar sized or larger buildings to all small areas of landuse=residential. In some cases we have added all buildings and the dividing hedge/fence between plots, but regard this as optional and maybe overkill/over use of memory/rendering-CPU-time/etc. In larger residential areas such as Meriden and Berkswell we have not added any buildings to contrast village with hamlet/mansions/etc., but would welcome other local editors to take on such tasks over time. In larger areas still, it is obvious by adding all the residential roads that the grey area is residential. 
Buildings for farm use are default labelled as building=agricultural, unless the specific use is known, e.g building=glasshouse

3.  We have  tried to give a landuse to all light grey areas other than the verges of roads and some tracks and footpaths. Sometimes this needed lateral thinking to define an area by its major use to avoid leaving light grey bits of scrubland, etc. 

4.  Being surrounded by large residential areas where horse riding is popular amongst the residents there is  a large amount of farmland devoted to grazing and exercising horses: these we have differentiated by using landuse=meadow. It is often hard to get this right, for example the meadows north of Pickford Grange Farm are usually full of horses, but checking with Google StreetView shows cattle in the eastern 2 or 3  so we’ve left them meadow). There are other areas which are probably anomalies but regular ground surveying and more discussion will eventually clear these up.
5. Landuse=forest has only been used where it is obvious by the regular pattern of the trees that it  is a planted and managed area of trees. All other wooded areas are tagged natural=wood. Currently we are not sure that we have been totally consistent here. There can also be ambiguity between a line of trees, a thin wood and a thick hedge,especially along watercourses. Much here is a matter of styles between individual mappers.

Issues

A. The brown colouring of the farmland we hope one day soon be made lighter/brighter. The current brown is not, to us, aesthetically pleasing, and  makes seeing highway=footway paths hard to see. The residential grey has almost as bad an effect. 
It may be a good idea to render footways somewhat wider (especially at larger scales), and/or increase the width of lightening the background which works so well with woods and forests. 

B  We have been adding a lot more of the stiles and kissing gates. Unfortunately the latter do not get rendered whereas gates, bollards and stiles do. Kissing gates locations are useful to know if you need to navigate with persons who can walk adequately but have mobility difficulty in crossing stiles or you have a very large dog which you can’t lift over stiles bit you can get though kissing gates. We can’t rely on the absence of stiles on the map to infer a walkable  route in these circumstances ( incomplete surveying), but the explicit rendering of kissing gates would be a great asset.

When is a boundary not a boundary?

10 Februaury 2013, RobJN

Boundaries, be they land ownership or administrative boundaries, form an essential part of geo-data. Was it therefore a success for the open data campaign when Ordnance Survey released the Boundary-Line product, containing all electoral and administrative boundaries, under the OS OpenData Licence? Not Quite.

The problem is that boundary is the “Boundary-Line” data are not boundaries! There are two issues, and these apply to all geospatial data released as independent vector layers; scale and context.

Scale

Large scale maps (such as walking maps), have a higher resolution than medium, or small scale maps (such as country of global maps). The larger the scale, the higher the resolution and therefore the more detail shown. As boundaries twist and turn following streams, rivers and hedges, it is important to use a large scale/high resolution. The Ordnance Survey provide boundary data in two products; the free “Boundary-Line” product, and the non-free “OS MasrterMap” product. According to Ordnance Surveys own admission:

Boundary-Line is captured against a lower resolution mapping backdrop and the boundaries are captured to represent the data at a nominal 1:10000 viewing scale. The process of generalising the data may have caused some features to be moved from their true ground position for the purpose of map clarity.

So scale, or to give it it's proper name, generalisation, is the first problem we should be aware of before using Boundary-Line data in OpenStreetMap.

Context

Lets see what Ordance Survey have to say about their other boundary product – OS MasterMap:

OSMM Topography Layer currently holds the definitive and more accurate boundary information as the boundaries are mered (aligned to) real-world features on the ground. Captured at mapping scales of 1:1250, 1:2500 (for urban areas) and 1:10k (for rural).

Okay, we can see that MasterMap uses a larger scale / higher resolution which helps provide more accurate data, but what is that reference to “mereing” (alignment). Mereing, is the process of establishing a boundary relative to ground features present at the time of a survey (source: ESRI). As such any boundary line extracted from a map of any resolution cannot therefore be used on its own to describe a boundary – once you extract the boundary, you loose the context provided by the rest of the map!
Lets look at an example.

For illustration purposes only (courtesy of Ordnance Survey and Coventry City Council).

In the example above we see the boundary as a black dashed line. Along the line are some descriptions in pink. The first couple are relatively easy to decipher - “Co Const Met Dist & CP Bdy” is shorthand for County Constituency, Metropolitan District and Civil Parish boundary. Similarly “Boro Const Bdy” tells us it is a Borough Constituency boundary. As we follow the boundary we reach more abstract shorthand:

• 1.22m RH – RH stands for Root of Hedge, and 1.22m equates to exactly 4ft. The boundary is therefore 4ft away from the stem line of the hedge. This unusual convention comes from the presumption that landowners planted hedgerows slightly in from the edge of their land so as to not encroach on their neighbours plots. The distance differs between 3ft and 5ft depending on which parish the land lies within.
• Def – This is a “defaced boundary”, meaning that the original feature that the boundary was aligned to no longer exists. This was probably a hedge that was removed when the houses were built. Had the hedge roots not been removed then the boundary would be marked as “Tk H” implying track of hedge.
• Und - An “undefined boundary” is one where there was no real-world feature to align the boundary to when it was surveyed.

For a list of abbreviations click here.

Conclusion

Any vector extract of boundary data will be problematic due to generalisation (scale) and the loss of information about mereing (loss of context). If you are really keen on determining the exact boundary you may want to read more about boundary presumptions or go and dig out the original surveyors notes (Perambulation Cards) at the National Archives.

Discussion

So for OpenStreetMap should we be linking boundary ways to streams and hedges on the acknowledgement that Boundary-Line data is not perfect and we are not able to provide any certainty as to which side of the hedge the boundary actually resides on? Please leave your thoughts as comments below.