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I am currently using the OpenLayers plugin to import google maps as the base layer for a heat map. The map is of population by census tract. The more populous census tracts are red and less populous green.

This is working well but the openlayer is completely flat and 0% transparent. This means I have to have my coloured census tracts over the top which obscures the features of the map.

In products like MapPoint you are able to have the background of the map at the very back, then the coloured data and then the labels (cities, highways etc) at the top. Does anyone know how I can do that?

Another option would be a transparent map layer which I could then put over the top of my coloured census tracts.

Any help would be much appreciated.

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2 Answers 2

Everything is possible with QGIS also. Hopefully this is what you are trying to achieve.

  1. Keep your layer order such that Points and Line Layers are at the top followed by any polygon layers.
  2. Keep "OpenLayers" layer at the bottom of all layers(like a base layer) in the Layers List. You can Drag and drop to achieve this.

enter image description here

Set transparency to any layer by right-clicking the layer and adjusting the transparency slider in the style tab as shown below.

transparency settings

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Hi vinayan, thanks for your reply. Unfortunately I don't have any road / place name layers. I was using the open layers google streets for that. This is what I have at the moment: i46.tinypic.com/140vvkg.jpg. I tried downloading the OSM data from cloudmade for the whole of georgia state but overlaying that results in much too much detail. I then tried underdark's google style: underdark.wordpress.com/2011/09/16/… but because the map is quite zoomed out that didn't really work either. Do you know where I can get highway layers that are simple? –  user8575 Jul 3 '12 at 16:18
    
@user8575 - download TIGER shapefiles from census.gov/geo/www/tiger/tgrshp2011/tgrshp2011.html ... you can show US Highways by querying the 'RTTYP = U' from this shapefile –  vinayan Jul 3 '12 at 16:32
    
Amazing! That works really well. Thanks so much! Do you know if I can do the same for cities and towns? Is there another tiger file for that? –  user8575 Jul 3 '12 at 16:47
    
@user8575 - not sure about cities..you can refer 2011 TIGER/Line Shapefiles Technical Documentation pdf to see if anything is there –  vinayan Jul 4 '12 at 0:05

You can also use the data provided by Natural Earth: http://www.naturalearthdata.com/downloads/

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Thanks! That's a good resource. –  user8575 Jul 4 '12 at 12:53

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