Some eye candy from my experiments of combining Nearmap terrain tiles with OpenStreetMap tiles. These images (which are hyperlinked to full sized ones) are derived works from OpenStreetMap.org default mapnik tiles (which is based on data from OpenStreetMap contributors licensed CC BY-SA 2.0), and Nearmap.com shaded relief terrain maps licensed under the Nearmap Community License.

[caption id="attachment_1198" align="aligncenter" width="600" caption="Nearmap Terrain Maps with OpenStreetMap Mapnik Map. Based on images (c) OpenStreetMap contributors, CC-BY-SA, and (c) Nearmap, Nearmap Community License."][/caption]

[caption id="attachment_1199" align="aligncenter" width="600" caption="Nearmap Terrain Maps with OpenStreetMap Mapnik Map. Based on images (c) OpenStreetMap contributors, CC-BY-SA, and (c) Nearmap, Nearmap Community License."][/caption]

[caption id="attachment_1200" align="aligncenter" width="600" caption="Nearmap Terrain Maps with OpenStreetMap Mapnik Map. Based on images (c) OpenStreetMap contributors, CC-BY-SA, and (c) Nearmap, Nearmap Community License."][/caption]

[caption id="attachment_1201" align="aligncenter" width="600" caption="Nearmap Terrain Maps with OpenStreetMap Mapnik Map. Based on images (c) OpenStreetMap contributors, CC-BY-SA, and (c) Nearmap, Nearmap Community License."][/caption]

[caption id="attachment_1202" align="aligncenter" width="600" caption="Nearmap Terrain Maps with OpenStreetMap Mapnik Map. Based on images (c) OpenStreetMap contributors, CC-BY-SA, and (c) Nearmap, Nearmap Community License."][/caption]

My approach is based on http://wiki.openstreetmap.org/wiki/TopOSM/Details. I used two mapnik stylesheets, one for everything minus the labels, and one with just the labels. From here I used this bash script,

[sourcecode language="bash"] for f in nearmap-dem///* do f=echo $f|sed 's/[^\/]*\///' #get rid of the nearmap-dem part d=dirname $f mkdir -p "grayshaded/$d"

convert "nearmap-dem/$f" -colorspace gray "grayshaded/$f" #just convert to gray

...alternatively, extract the Lightness channel...

convert "nearmap-dem/$f" -separate -channel Lightness -colorspace gray "grayshaded/$f" lastdir=dirname "grayshaded/$f" lastfile=basename "grayshaded/$f" .png rm -f "$lastdir/$lastfile-0.png" "$lastdir/$lastfile-2.png" mv "$lastdir/$lastfile-1.png" "$lastdir/$lastfile.png" done [/sourcecode]

to convert a directory of Nearmap Terrain tiles into something suitable to be passed in as the hillshade layer to the combine script at http://wiki.openstreetmap.org/wiki/TopOSM/Details#Combining_images_into_a_final_composite, and then I used combine script to merge the layers together for each tile.

Update: The Mapnik stylesheets I used for labels and nolabels are at http://gist.github.com/653184

So a while back Geoscience Australia stuck this notice on their website,

Unless otherwise noted, all Geoscience Australia material on this website is licensed under the Creative Commons Attribution 3.0 Australia Licence.

Great, another source of free government data. So today when I find a use for some data held on their site I was very dissapointed to see,

"Please note: Any organisation or individual wanting to use the Gazetteer data in a similar capacity to the Online Place Name Search or any other online application, will require an Internet user licence. (See the Licence Fees and Order Form below)."

So much for the CC-BY license. The latter notice is an "otherwise noted" which says, this data is NOT CC-BY because if you want to use it for such an such purpose you need to get another license to allow you to do that.

...I was thinking, short of having a high resolution accurate computer model of the world (i.e. digital terrain model with an orthophoto on the terrain + accurate 3D models of buildings, bridges, trees, etc), one can use these "oblique" aerial views to similate other low angle views.

[caption id="attachment_1178" align="aligncenter" width="573" caption="Sydney North Oblique view. Image tiles from NearMap. Used under the http://www.nearmap.com/products/community-licence license."][/caption]

What I mean is that Google Earth uses orthophotos as the ground texture. For some places they also have rough building models and these make low angles (ie. when you are not looking straight down towards the earth's surface) in Google Earth look a little bit more real. An alternative, when we lack a high resolution accurate model, for an interactive Google Earth like application is to use overhead orthorectified imagery when the user is looking from above, and use the oblique views (called MultiView on NearMap) when the angle between the direction of view and the ellipsoid surface normal gets larger. For a 2D web interface when the user changes from the overhead imagery to the oblqiue views, the imagery could fade from one to the other.

[caption id="attachment_1179" align="aligncenter" width="600" caption="Sydney North Oblique viewed in Google Earth from a lower angle (not straight above). Image tiles from NearMap. Used under the http://www.nearmap.com/products/community-licence license."][/caption]

I hope to also get libchamplain to overlay transpanent map tiles on top of imagery (more on that in the next post), because I really think that oblique views make map reading much easier for the user (although the South, East and West can be a little confusing when viewed at high zooms on a 2D map, just like looking at the world map upside down can be a little confusing at first you just have to think a little bit harder to work out what your looking at, see South and East views further below).

[caption id="attachment_1181" align="aligncenter" width="600" caption="Sydney North Oblique Imagery from NearMap with OpenStreetMap tiles on top. OSM tiles and data CC-BY-SA 2.0 http://www.openstreetmap.org/, NearMap imagery http://www.nearmap.com/products/community-licence."][/caption]

[caption id="attachment_1182" align="aligncenter" width="600" caption="North Oblique Imagery from NearMap with OpenStreetMap tiles on top. OSM tiles and data CC-BY-SA 2.0 http://www.openstreetmap.org/, NearMap imagery http://www.nearmap.com/products/community-licence."][/caption]

[caption id="attachment_1183" align="aligncenter" width="600" caption="Sydney South Oblique View. Image tiles from NearMap. Used under the http://www.nearmap.com/products/community-licence license."][/caption]

[caption id="attachment_1184" align="aligncenter" width="600" caption="Sydney East Oblique View. Image tiles from NearMap. Used under the http://www.nearmap.com/products/community-licence license."][/caption]

Soon I'll post up some stuff about NearMap in libchamplain, and my plans to set up some kind of object recognition to find objects like zebra crossings, the yellow school zone rectangle, cars... from imagery for integration into OpenStreetMap.