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Towards Creating General Melchett's Map

Posted by SomeoneElse on 2 September 2016 in English (English)

I've written before about the changes needed to render more zoom levels than 18 with a "Switch2Osm-style" tile server.

However, sometimes zoom level 20 isn't enough. Here:

nott_ajt_20.png

is part of Nottingham at zoom level 20. At least one of the office names doesn't appear (it corresponds to here in OSM). The problem is that the way that the "standard" renderd stores metatiles means that only a certain number of tiles can be stored for each zoom level (see this list post for the details). In order to store more I changed renderd slightly so that more zoom levels can be stored - see here and here for the details.

Rendering works fine at higher zoom levels (up to 28 in my example) so that all of those office names now appear. Here's the same area at zoom level 21:

nott_ajt_21.png

The principle could be extended to an eventual goal of 1:1 to keep Melchett and Darling happy (roughly zoom level 32 at this latitude) but that seems unnecessary even to me currently.

Long Distance Footpaths

Posted by SomeoneElse on 3 July 2016 in English (English)

Although plenty of maps have displayed long distance footpath information for ages, I'd always assumed that it would take a lot of extra processing to get working. Turns out I was wrong:

Brassington showing the Midshires Way, Limestone Way and High Peak Trail

Because of the way that relations are handled within osm2pgsql, converting route relations into "just another highway type" is pretty straightforward, and once created that new "highway=ldpnwn" can be added to the stylesheet.

In this case the two things to think about are the fill and the text. The "fill" is a short wide purple dot separated by a long gap from the next one. In the code (see the links above) at "line-dasharray" the "1" says "short and the "60" says "separated by a long gap" and further down the "line-width: 4" says "wide".

The text for most names in the stylesheet is handled in one place. Long distance paths have to be different to distinguish them from road names, and so the text fill is purple, the text-dy larger to place it further from the road and text-spacing is further apart at higher zoom levels.

The big advantage of handling relations "just like any other road" is that all the clever Mapnik stuff "just works" - like text going around corners:

Text going around a corner from some steps onto a road

Creating a Garmin map using "mkgmap" - a very simple example

Posted by SomeoneElse on 14 May 2016 in English (English)

On many occasions in the past I've said "it's really easy to create your own Garmin maps" but I don't think I've ever documented the procedure. This is an attempt to do that.

Assumptions:

You've got some sort of Garmin device with an SD card in it with some maps that you've downloaded from somewhere on it.

You want to replace those with a map you've created yourself.

You've got a PC with around enough memory in it. The one I used for the examples below had 4Gb; it's possible that less may be needed for a small file such as the one used in the examples below.

All the path examples below for for Windows (actually tested on Windows 7), but it should be relatively straightforward to adapt them to work on other operating systems.

What you need to do

The easiest way to create Garmin maps from OSM data is to use "mkgmap". That's available from:

http://www.mkgmap.org.uk/

The download page for the latest mkgmap is http://www.mkgmap.org.uk/download/mkgmap.html and the current version is "3676".

Unzip the zip file and move the folders intact to a known location. In my case I moved it so that "mkgmap.jar" file was in: C:\Utils\mkgmap-r3676

I didn't use a path with a space in it or a path that Windows recognises as "special" to avoid any possible confusion later.

"Splitter" is a separate program used to split a large OSM data file into portions small enough for mkgmap to work with (the resultant Garmin map can still route between portions).

The latest Splitter is here: http://www.mkgmap.org.uk/download/splitter.html and the current version is "437".

Unzip the zip file and move the folders intact to a known location. In my case I moved it so that splitter.jar was in: C:\Utils\splitter-r437

Next, we need to download an OSM extract to use to create maps from. As an example I'll use Romania, and extract for which can be downloaded from here:

http://download.geofabrik.de/europe/romania.html

That page currently says:

romania-latest.osm.pbf, suitable for Osmium, Osmosis, imposm, osm2pgsql, mkgmap, and others. This file was last modified 7 hours ago and contains all OSM data up to 2016-05-13T19:45:03Z. File size: 146 MB; MD5 sum: b0554ae9632cc6c2be1c1e3525b5dcb5.

After downloading, check that the file is intact:

md5sum romania-latest.osm.pbf b0554ae9632cc6c2be1c1e3525b5dcb5 *romania-latest.osm.pbf

(see links from https://en.wikipedia.org/wiki/Md5sum for where to get an "md5sum" program from if you don't already have one)

That matches so we can continue.

Create a directory to work in - in my case I created "D:\doc\gps\romania" and copied romania-latest.osm.pbf to it.

From a command prompt (on Windows), change the current directory to be where the downloaded .pbf file is.

d:
cd \doc\gps\romania

See what version of "java" you have installed. Type "java -version" at the command prompt to find out. In my case that says:

java version "1.8.0_91" Java(TM) SE Runtime Environment (build 1.8.0_91-b14) Java HotSpot(TM) 64-Bit Server VM (build 25.91-b14, mixed mode)

so Java is already installed. If you don't already have Java installed download and install from somewhere like: http://java.com/en/download/windows_xpi.jsp

Next, run splitter. The "-Xmx1200m" tells it how much memory to allocate; the "--max-nodes" how big to make each split piece. The examples for the parameters given here should "just work":

java  -Xmx1200m -jar c:\utils\splitter-r437\splitter.jar romania-latest.osm.pbf --max-nodes=800000 --output=xml

That should create lots of ".osm.gz" files. Then run mkgmap. Here "--style" determines the style of map to create - "default" is actually a folder containing several files that make up that style. Unsurprisingly the style called "default" is the default mkgmap style - not particularly optimised for foot, bicycle or car use.

java -Xmx1200M -jar C:\Utils\mkgmap-r3676\mkgmap.jar --style-file=C:\Utils\mkgmap-r3676\examples\styles\default  --route --gmapsupp *.osm.gz

When that finishes it should say something like "Total time taken: 621133ms" (i.e. about 10 minutes on a fairly slow PC for a country that is relatively small in OSM terms).

That creates:

d:\doc\gps\romania:
-rw-rw-rw-  1 A.Townsend None 123359232 05-14 13:31 gmapsupp.img
-rw-rw-rw-  1 A.Townsend None      4270 05-14 13:31 osmmap.tdb
-rw-rw-rw-  1 A.Townsend None     73728 05-14 13:31 osmmap.img

Create a subdirectory and move those files into there for safekeeping:

d:\doc\gps\romania\default:
-rw-rw-rw-  1 A.Townsend None 123359232 05-14 13:31 gmapsupp.img
-rw-rw-rw-  1 A.Townsend None     73728 05-14 13:31 osmmap.img
-rw-rw-rw-  1 A.Townsend None      4270 05-14 13:31 osmmap.tdb

Copy those files to the GPS. The method to do this varies by device. I'd expect that people reading this will already do this with files they've downloaded from elsewhere; if not there are lots of examples on places such as http://help.openstreetmap.org.

When it's copied across, turn on the GPS and check that the new map is visible.

Next, how to change the style slightly?

In C:\Utils\mkgmap-r3676\examples\styles, take a copy of the "default" folder and call it something like "mystyle". We'll leave "default" as it was and make a simple change to "mystyle". As a test we're going to make tracks appear like unclassified roads.

Edit c:\Utils\mkgmap-r3676\examples\styles\mystyle\lines in a text editor. The "lines" file is the one that deals with linear items - things such as roads.

Here's the line in that file that deals with unclassified roads:

highway=unclassified [0x06 road_class=0 road_speed=3 resolution 21]

It's pretty straightforward what is happening - the OSM feature at the left ("highway=unclassified") is to be transformed into the Garmin feature at the right ("0x06").

Here's the line that deals with tracks:

highway=track [0x0a road_class=0 road_speed=1 resolution 22]

change the latter line to:

highway=track [0x06 road_class=0 road_speed=3 resolution 21]

(i.e. so that "highway=track" is treated as if it was "highway=unclassified")

Rerun mkgmap with the new style:

java -Xmx1200M -jar C:\Utils\mkgmap-r3676\mkgmap.jar --style-file=C:\Utils\mkgmap-r3676\examples\styles\mystyle  --route --gmapsupp *.osm.gz

Create somewhere safe to store the new files, and put them there:

d:\doc\gps\romania\mystyle:
-rw-rw-rw-  1 A.Townsend None 123338752 05-14 14:23 gmapsupp.img
-rw-rw-rw-  1 A.Townsend None     73728 05-14 14:23 osmmap.img
-rw-rw-rw-  1 A.Townsend None      4270 05-14 14:23 osmmap.tdb

Copy to the GPS again, and check that tracks do indeed appear as roads.

... and that's it.

Obviously there are many more changes that can be made. There's quite a lot of information on the OSM wiki at places such as http://wiki.openstreetmap.org/wiki/Mkgmap/help .

The resulting example "default" files can be found at this link:

https://drive.google.com/open?id=0BwHcCIjlU11ucl9HYzdzdmc1OGs

The resulting example "mystyle" files can be found at this link:

https://drive.google.com/open?id=0BwHcCIjlU11ueWlTX1J5Q3paUnM

Trees (again)

Posted by SomeoneElse on 26 April 2016 in English (English)

A while back I described how I was showing tree types in woodland. The "unfinished business" there was "what about forest areas where the trees have been cleared?". Mapping of that is a bit hit and miss. "Forestry" has been suggested, but doesn't have many takers, and "forest" is actually often used for "the entire forestry area" (at least where I'm interested in rendering tiles for - I suspect it varies considerably worldwide). The wiki page and the standard style rendering discussion don't distinguish, but I thought it was worth trying to separate out "natural=wood" and "landuse=forest" where the latter is used for "the entire forestry area, including where there are currently no trees".

Here's the result:

Trees east of Bolsover

That corresponds to here in OSM's standard style. The dark green bit corresponds to "trees" (natural=wood; if there's a surveyed leaftype then obviously that is shown too). The lighter green bit means "forest, but no trees" (landuse=forest - the lighter green is only visible if there's no natural=wood also there). The forest and wood colours are defined here; here is the leaf_type handling in the stylesheet and here is where the natural and landuse tags are checked to see whether the current object should be treated as "trees with a known leaf type", "trees without a known leaf type" or "forest, but not necessarily trees".

Sidewalks!

Posted by SomeoneElse on 13 March 2016 in English (English)

(or if you're English, "Pavements!")

I finally got this working for tertiary and secondary roads:

Sidewalk rendering example

That location corresponds to here in OSM.

There were three bits to it:

1) Determining which roads should have a sidewalk rendered. This is done in lua, and creates e.g. a road type "tertiary_sidewalk" to go with "tertiary" and "tertiary_link":

https://github.com/SomeoneElseOSM/SomeoneElse-style/blob/sidewalk/style.lua#L230

2) Handle "tertiary_link" the same as "tertiary" in the style's MML, e.g.:

https://github.com/SomeoneElseOSM/openstreetmap-carto-AJT/blob/sidewalk/project.mml#L403

3) Handle "tertiary_link" the same as "tertiary" in the style's roads.mss, e.g.:

https://github.com/SomeoneElseOSM/openstreetmap-carto-AJT/blob/sidewalk/roads.mss#L2363

... except where we want to do something different:

https://github.com/SomeoneElseOSM/openstreetmap-carto-AJT/blob/sidewalk/roads.mss#L1114

"sidewalk_width-z13" etc. are declared at the top:

https://github.com/SomeoneElseOSM/openstreetmap-carto-AJT/blob/sidewalk/roads.mss#L119

There's scope for further tinkering, and I've yet to see how usable it is on a small mobile phone screen in poor light, but it looks OK so far...

Trees!

Posted by SomeoneElse on 14 June 2015 in English (English)

As you may be aware, mapping of areas of trees in OSM is complicated. It's not possible to tell just by looking at the data which of the four(!) approaches described on that page someone is using "natural=wood" and/or "landuse=forest" to mean. It therefore didn't make a lot of sense to me to display them differently on a map created from OSM data.

Last year there was a proposal to record "leaf_type" and "leaf_cycle" separately, which makes sense (though the wider range of non-European tree types doesn't seem to be catered for as well as previously. Unfortunately a previous version of that page suggested that "wood=deciduous" should be replaced by "leaf_type=broadleaved", and a no doubt well-meaning non-local mapper decided to change some areas of mainly deciduous woodland to "leaf_type". Whilst some of these were correct, clearly there are some issues with this, but as I was changing some that I did have local knowledge of, the thing that mainly struck me was that the situation on the ground was far more complicated than previously mapped, or rendered, on OpenStreetMap. I therefore decided to start trying to record "leaf_type" and (when there was enough data, render it. Initial results can be seen here: Trees in Clipstone That location corresponds to here in OSM. There's a lot more to do there, but at least there's a bit more detail than "a large area of trees".

That rendering is created by a combination of this lua script at osm2pgsql data import time and this stylesheet. It's primarily designed for showing England-and-Wales-specific rights of way, but trees seemed like a natural extension.

Notes and Fixmes

Posted by SomeoneElse on 22 December 2014 in English (English)

A while back I wrote https://github.com/SomeoneElseOSM/Notes01 to enable OSM notes to be converted to a useful Garmin format so that you can actually check them when out and about.

A week ago I added support for extracting "fixme" tags from Overpass. There are about 20 notes within 9km of my house, so I was interested to see how many fixmes there were. It turned out that there were 430! As someone said on IRC, "that'll keep you busy over Christmas".

Best Regards,

Andy

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Posted by SomeoneElse on 16 September 2009 in English (English)

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