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资源说明：cartoCSS / carto vélo
Vélosm
******
Introduction
============
Trying to build a nice map for everyday cyclists.
To achieve that, we have at least the following goals:
* Make streets less visible that aren't cycliste friendly
* Exagerate relief data to know when it's going to be hard (or fun)
Getting things running
======================
We use TileMill http://mapbox.com/tilemill/ to configure the rendering of the
map.
If you create a directory in ~/Documents/MapBox/project/ containing the
``project.mml`` and ``style.mss`` files. Edit ``project.mml`` to set the different sources
(we will have to improve this!).
StreetData comes from OpenStreetMap, imported with http://imposm.org into
a http://postgis.refractions.net/ database.
At last, elevation data comes from the *Shuttle Radar Topography Mission (SRTM)*
Elevation
=========
Most instructions are based on : http://mapbox.com/tilemill/docs/guides/terrain-data/
We used GDAL (http://www.gdal.org/) to convert those elevation data.
#. Get elevation data as a tiff file http://srtm.csi.cgiar.org/
#. Reproject into the "google"-projection::
glwarp -s_srs EPSG:4269 -t_srs EPSG:900913 srtm_37_03.tif projected_srtm.tif::
#. Generate a hillshade file. It will cast a shadow on one side of the hills. We use -s 0.2 to exagerate the shading::
gdaldem hillshade -s 0.2 -co compress=lzw projected_srtm.tif hillshade_srtm.tif
#. Generate a file that indicates steep slopes::
gdaldem slope projected_srtm.tif slope_srtm.tif
#. However, we want some colors to that. We say that flat is white, 5° orange and 10° red. So we write a file ``slope_ramp.txt`` containing::
0 255 255 255
5 255 127 0
10 255 0 0
#. We generate the file with colors::
gdaldem color-relief -co compress=lzw slope_srtm.tif slope_ramp.txt slope_srtm_color.tif
#. We might also want some elevation contour, at 10 and 50 meters::
gdal_contour -a elev projected_srtm.tif contour10.shp -i 10.0
gdal_contour -a elev projected_srtm.tif contour50.shp -i 50.0
When importing the raster layers (``slope_srtm_color.tif`` and ``hilshade.tif``),
we need to specify the following styles in order to have a better interpolation
and to merge the layers::
#hillshadesrtm, #slopesrtmcolor {
raster-scaling: bilinear;
raster-comp-op: multiply;
}
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