Advertisements

Steve Bennett blogs

…about maps, open data, Git, and other tech.

Tag Archives: terrain

Cycletour.org: a better map for Australian cycle tours

Cycletour.org is a tool for planning cycle tours in Australia, and particularly Victoria. I made it because Google Maps is virtually useless for this: poor coverage in the bush and inappropriate map styling make cycle tour planning a very frustrating experience.

Let’s say we want to plan a trip from Warburton to Stratford, through the hills. This is what Google Maps with “bicycling directions” offers:

Google Maps - useless for planning cycle tours.

Google Maps – useless for planning cycle tours.

Very few roads are shown at this scale. Unlike motorists, we cyclists want to travel long distances on small roads. A 500 kilometre journey on narrow backstreets would be heaven on a bike, and a nightmare in a car. So you need to see all those roads when zoomed out.

Worse, small towns such as Noojee, Walhalla and Woods point are completely missing!

Enter Cycletour.org:

Screenshot 2015-01-09 18.03.59

You can plan a route by clicking a start and end, then dragging the route around:

Screenshot 2015-01-13 23.43.12

It doesn’t offer safe or scenic route selection. The routing engine (OSRM) just picks the fastest route, and doesn’t take hills into account. You can download your route as a GPX file, or copy a link to a permanent URL.

Cartography

The other major features of cycletour.org’s map style are:

Screenshot 2015-01-09 18.12.04Bike paths are shown prominently. Rail trails (old train lines converted into bike paths) are given a special yellow highlighting as they tend to be tourist attractions in their own right.

Train lines (in green) are given prominence, as they provide transport to and from trips.

 

 

Screenshot 2015-01-09 18.20.23Towns are only shown if there is at least one food-related amenity within a certain distance. This is by far the most important information about a town. Places that are simply “localities” with no amenities are relegated to a microscopic label.

 

 

Screenshot 2015-01-09 18.27.40Major roads are dark gray, progressing to lighter colours for minor roads. Unsealed roads are dashed. Off-road tracks are dashed red lines. Tracks that are tagged “four-wheel drive only” have a subtle cross-hashing.

And of course amenities Screenshot 2015-01-09 18.57.40useful to cyclists are shown: supermarkets, campgrounds, mountain huts, bike shops, breweries, wineries, bakeries, pubs etc etc. Yes, well-supplied towns look messy, but as a user, I still prefer having more information in front of me.

Terrain

Screenshot 2015-01-09 19.11.23The terrain data is a 20 metre-resolution digital elevation model from DEPI, within Victoria, trickily combined with a 90m DEM elsewhere, sourced from SRTM (NASA). I use TileMill‘s elevation shading feature, scaled so that sea level is a browny-green, and the highest Australian mountains (around 2200m) are white, with green between. 20-metre contours are shown, labelled at 100m intervals.

I’m really happy with how it looks. Many other comparable maps have either excessively dark hill shading, or heavy contours – or both.

Screenshot 2015-01-09 19.21.02

4UMaps

Screenshot 2015-01-09 19.20.35

Komoot

Screenshot 2015-01-09 19.20.24

OpenCycleMap

Screenshot 2015-01-09 19.20.15

Sigma

Mapbox Outdoors

Google Maps (terrain mode)

Screenshot 2015-01-09 19.35.37

MapBox Outdoors

 

Other basemaps

Screenshot 2015-01-09 19.39.25

VicMap

I’ve included an assortment of common basemaps, including most of the above. But the most useful is perhaps VicMap, because it represents a completely different data source: the government’s official maps.

Layers

Vegetation

Vegetation

There are also optional overlays. Find a good spot to stealth camp with the vegetation layer.

Or avoid busy roads with the truck volume layer. This data comes from VicRoads.Screenshot 2015-01-09 19.47.43

The bike shops layer makes contingency planning a bit easier, by making bike shops visible even when zoomed way out. The data is OpenStreetMap, so if you know of a bike shop that’s missing (or one that has since closed down), please update it so everyone can benefit.

Screenshot 2015-01-14 00.06.20

Mobile

Unfortunately, the site is pretty broken on mobile. But you can download the tiles for offline use on your Android phone using the freemium app Maverick. It works really well.

Other countries

Screenshot 2015-01-14 00.46.05

is.cycletour.org for Iceland. Yes, it’s real – but I don’t know how long I will maintain it.

It’s a pretty major technical undertaking to run a map for the whole world. I’ve automated the process for setting up cycletour.org as much as possible, and created my own version for Iceland and England when I travelled there in mid 2014. If you’re interested in running your own, get in touch and I’ll try to help out.

 

 

 

Feedback?

I’d love to hear from anyone that uses cycletour.org to plan a trip. Ideas? Thoughts? Bugs? Suggestions? Send ’em to stevage@gmail.com, or on Twitter at @Stevage1.

Advertisements

Terrain in TileMill: a walkthrough for non-GIS types

I created a basemap for http://cycletour.org with TileMill and OpenStreetMap. It looked…ok.

Image

But it felt like there was something missing. Terrain. Elevation. Hills. Mountains. I’d put all that in the too hard basket, until a quick google turned up two blog posts from MapBox, the wonderful people who make TileMill. “Working with terrain data” and “Using TileMill’s raster-colorizer“. Putting these two together, plus a little OCD, led me to this:

Image

Slight improvement! Now, I felt that the two blog posts skipped a couple of little steps, and were slightly confusing on the difference between the two approaches, so here’s my step by step. (MapBox, please feel free to reuse any of this content.)

My setup is an 8 core Ubuntu VM with 32GB RAM and lots of disk space. I have OpenStreetMap loaded into PostGIS.

1. Install the development version of TileMill

You need to do this if you want to use the raster-colorizer. You want this while developing your terrain style, if you want the “snow up high, green valleys below” look. Without it, you have to pre-render the elevation color effect, which is time consuming. If you want to tweak anything (say, to move the snow line slightly), you need to re-render all the tiles.

Fortunately, it’s pretty easy.

  1. Get the “install-tilemill” gist (my version works slightly better)
  2. Probably uncomment the mapnik-from-source line (and comment out the other one). I don’t know whether you need the latest mapnik.
  3. Run it. Oh – it will uninstall your existing TileMill. Watch out for that.
  4. Reassemble stuff. The dev version puts projects in ~/Documents/<username/MapBox/project which is weird.

2. Get some terrain data.

The easiest place is the ubiquitous NASA SRTM DEM (digital elevation model) data. You get it from CGIAR. The user interface is awful. You can only download pieces that are 5 degrees by 5 degrees, so Victoria is 4 pieces.

Screen shot 2013-09-11 at 10.46.00 PM

If you’re downloading more than about that many, you’ll probably want to automate the process. I wrote this quick script to get all the bits for Australia:

for x in {59..67}; do
for y in {14..21}; do
echo $x,$y
if [ ! -f srtm_${x}_${y}.zip ]; then
wget http://droppr.org/srtm/v4.1/6_5x5_TIFs/srtm_${x}_${y}.zip
else
echo "Already got it."
fi
done
done
unzip '*.zip'


3. Process SRTM .tifs with GDAL.

To have any fun with terrain mapping in TileMill, you need to produce separate layers from the terrain data:

  1. The heightmap itself, so you can colour high elevations differently from low ones.
  2. A “hillshading” layer, where southeast facing slopes are dark, and northwest ones are light. This is what produces the “terrain” illusion.
  3. A “slopeshading” layer, where steep slopes (regardless of aspect) are dark. I’m ambivalent about how useful this is, but you’ll want to play with it.
  4. Contours. These can make your map look AMAZING.
Screen shot 2013-09-11 at 10.53.41 PM

Contours – they’re the best.

In addition, you’ll need some extra processing:

  1. Merge all the .tif’s into one. (I made the mistake of keeping them separate, which makes a lot of extra layers in TileMill). Because they’re GeoTiffs, GDAL can magically merge them without further instruction.
  2. Re-project it (converting it from some random ESPG to Google Web Mercator – can you tell I’m not a real GIS person?)
  3. A bit of scaling here and there.
  4. Generating .tif “overviews”, which are basically smaller versions of the tifs stored inside the same file, so that TileMill doesn’t explode.

Hopefully you already have GDAL installed. It probably came with the development version of TileMill.

Here’s my script for doing all the processing:

#!/bin/bash
echo -n "Merging files: "
gdal_merge.py srtm_*.tif -o srtm.tif
f=srtm
echo -n "Re-projecting: "
gdalwarp -s_srs EPSG:4326 -t_srs EPSG:3785 -r bilinear $f.tif $f-3785.tif

echo -n "Generating hill shading: "
gdaldem hillshade -z 5 $f-3785.tif $f-3785-hs.tif
echo and overviews:

gdaladdo -r average $f-3785-hs.tif 2 4 8 16 32
echo -n "Generating slope files: "
gdaldem slope $f-3785.tif $f-3785-slope.tif
echo -n "Translating to 0-90..."
gdal_translate -ot Byte -scale 0 90 $f-3785-slope.tif $f-3785-slope-scale.tif
echo "and overviews."
gdaladdo -r average $f-3785-slope-scale.tif 2 4 8 16 32
echo -n Translating DEM...
gdal_translate -ot Byte -scale -10 2000 $f-3785.tif $f-3785-scale.tif
echo and overviews.
gdaladdo -r average $f-3785-scale.tif 2 4 8 16 32
#echo Creating contours
gdal_contour -a elev -i 20 $f-3785.tif $f-3785-contour.shp

Take my word for it that the above script does everything I promise. The options I’ve chosen are all pretty standard, except that:

  • I’m exaggerating the hillshading by a factor of 5 vertically (“-z 5”). For no particularly good reason.
  • Contours are generated at 20m intervals (“-i 20”).
  • Terrain is scaled in the range -10 to 2000m. Probably an even lower lower bound would be better (you’d be surprised how much terrain is below sea levels – especially coal mines.) Excessively low terrain results in holes that can’t be styled and turn up white.

4. Load terrain layers into TileMill

Now you have four useful files, so create layers for them. I’d suggest creating them as layers in this order (as seen in TileMill):

  1. srtm-3785-contour.shp – the shapefile containing all the contours.
  2. srtm-3785-hs.tif – the hillshading file.
  3. srtm-3785-slope-scale.tif – the scaled slope shading file.
  4. srtm-3785.tif – the height map itself. (I also generate srtm-3785-scale.tif. The latter is scaled to a 0-255 range, while the former is in metres. I find metres makes more sense.)

For each of these, you must set the projection to 900913 (that’s how you spell GOOGLE in numbers). For the three ‘tifs’, set band=1 in the “advanced” box. I gather that GeoTiffs can have multiple bands of data, and this is the band where TileMill expects to find numeric data to apply colour to.

Screen shot 2013-09-11 at 11.06.39 PM

5. Style the layers

Mapbox’s blog posts go into detail about how to do this, so I’ll just copy/paste my styles. The key lessons here are:

  • Very slight differences in opacity when stacking terrain layers make a huge impact on the appearance of your map. Changing the colour of a road doesn’t make that much difference, but with raster data, a slight change can affect every single pixel.
  • There are lots of different raster-comp-ops to try out, but ‘multiply’ is a good default. (Remember, order matters).
  • Carefully work out each individual zoom level. It seems to work best to have hillshading transition to contours around zoom 12-13. The SRTM data isn’t detailed enough to really allow hillshading above zoom 13

My styles:

.hs[zoom <= 15] {
[zoom>=15] { raster-opacity: 0.1; }
[zoom>=13] { raster-opacity: 0.125; }
[zoom=12] { raster-opacity:0.15;}
[zoom<=11] { raster-opacity: 0.12; }
[zoom<=8] { raster-opacity: 0.3; }

raster-scaling:bilinear;
raster-comp-op:multiply;
}

// not really convinced about the value of slope shading
.slope[zoom <= 14][zoom >= 10] {
raster-opacity:0.1;
[zoom=14] { raster-opacity:0.05; }
[zoom=13] { raster-opacity:0.05; }
raster-scaling:lanczos;
raster-colorizer-default-mode: linear;
raster-colorizer-default-color: transparent;

// this combo is ok
raster-colorizer-stops:
stop(0, white)
stop(5, white)
stop(80, black);
raster-comp-op:color-burn;

}

// colour-graded elevation model
.dem {
[zoom >= 10] { raster-opacity: 0.2; }
[zoom = 9] { raster-opacity: 0.225; }
[zoom = 8] { raster-opacity: 0.25; }
[zoom <= 7] { raster-opacity: 0.3; }
raster-scaling:bilinear;
raster-colorizer-default-mode: linear;
raster-colorizer-default-color: hsl(60,50%,80%);
// hay, forest, rocks, snow

// if using the srtm-3785-scale.tif file, these stops should be in the range 0-255.
raster-colorizer-stops:
stop(0,hsl(60,50%,80%))
stop(392,hsl(110,80%,20%))
stop(785,hsl(120,70%,20%))
stop(1100,hsl(100,0%,50%))
stop(1370,white);
}
.contour[zoom >=13] {
line-smooth:1.0;
line-width:0.75;
line-color:hsla(100,30%,50%,20%);
[zoom = 13] {
line-width:0.5;
line-color:hsla(100,30%,50%,15%);
}

[zoom >= 16],
[elev =~ “.*00”] {
l/text-face-name:’Roboto Condensed Light’;
l/text-size:8;
l/text-name:'[elev]’;
[elev =~ “.*00”] { line-color:hsla(100,30%,50%,40%); }
[zoom >= 16] { l/text-size: 10; }
l/text-fill:gray;
l/text-placement:line;
}
}

And finally a gratuitous shot of Mt Feathertop, showing the major approaches and the two huts: MUMC Hut to the north and Federation Hut further south. Terrain is awesome!

Screen shot 2013-09-11 at 11.25.23 PM