[R-sig-Geo] resolution of openmap() raster layers

Agustin Lobo alobolistas at gmail.com
Sun Feb 28 18:30:26 CET 2016

I get an error at installing from github on MacOSX10.9.5 that I have reported
to https://github.com/environmentalinformatics-marburg/mapview/issues
and it is being dealt there.

With the cran version mapview_1.0.0, I have problems to select the
type of map, I always get the OSM one. I've tried both
nica <- getData("GADM", country="NIC", level=0)
as in your example and

Note that mapView() selects the correct map:
mapView(nica,map.types="Thunderforest.Landscape" )

Also, it seems to me that the mapView() display is always projected
(perhaps Pseudo Mercator epsg:3857 ?) even if the spatial object used
in mapView() has another CRS.
In other words
is displayed on Pseudo Mercator even if
[1] "+proj=longlat +datum=WGS84 +no_defs +ellps=WGS84 +towgs84=0,0,0"

Am I wrong?

Finally, is there a way of including an scale bar? Actually, this
option would be interesting even for interactive display.


On Fri, Feb 26, 2016 at 3:32 PM, Chris Reudenbach
<reudenbach at uni-marburg.de> wrote:
> Agus,
> Mapview is using leaflet as engine. Due to this you will have the control
> icons on the map because first of all it is designed for interactive mapping
> within RStudio/R.
> I think there are two different approaches to save your maps:
> If you want to have a dump of the mapviewobject (but including the graphical
> buttons) you'll find a descriptat stackoverflow
> http://stackoverflow.com/questions/31336898/how-to-save-leaflet-in-rstudio-map-as-png-or-jpg-file
> You may also use  the spplot function from mapview which is designed for
> basic static mapping and to make usable the adavantages of spplot.
> Note even if you are dealing with the mapview map object the spplot function
> uses the Openstreetmap package for retrieving  the background maps  (e.g.
> http://www.inside-r.org/packages/cran/OpenStreetMap/docs/openmap). You can
> use the spplot syntax for designing your maps. Up to now this static
> plotting function is still pretty  basic but you may have a try:
> spplot(mapView(nica["POP2000"]),colorkey=FALSE,  lwd= 15, alpha.regions =
> 0.9,
> map.type="stamen-watercolor" )
> I think for using the spplot it is better to install the current stable from
> github:
> library(devtools)
> install_github("environmentalinformatics-marburg/mapview", ref = "master")
> cheers chris
> Am 26.02.2016 um 12:27 schrieb Agustin Lobo:
>> Stunning!
>> Can I remove the buttons for saving to a bmp file?
>> What attribution should be used for publishing?
>> Agus
>> On Thu, Feb 25, 2016 at 7:42 PM, Chris Reudenbach
>> <reudenbach at uni-marburg.de> wrote:
>>> Hi,
>>> if you just want to map the data, mapview could be an option that among
>>> others avoid the pixel stretching.
>>> require(mapview)
>>> require(raster)
>>> nica <- getData("GADM", country="NIC", level=0)
>>> mapview(nica)
>>> mapview(nica,zcol = "POP2000", color = "#FFA500", lwd= 5, alpha.regions =
>>> 0.4)
>>> cheers Chris
>>> Am 25.02.2016 um 18:49 schrieb Barry Rowlingson:
>>>> On Thu, Feb 25, 2016 at 5:11 PM, Agustin Lobo <alobolistas at gmail.com>
>>>> wrote:
>>>>> Is there any way to download the raster layers
>>>>> of openmap() with an increased resolution?
>>>>> I find the quality of the labels very low,
>>>>> or am I doing something wrong? i.e.
>>>>> require(raster)
>>>>> require(mapmisc)
>>>>> nica <- getData("GADM", country="NIC", level=0)
>>>>> nicabg <- openmap(nica, path="landscape")
>>>>> plot(nicabg)
>>>>    Map tiles from OpenStreetMap and other map tile providers are images
>>>> designed to be shown at a fixed resolution. When you plot them in an R
>>>> graphics window you could be stretching them so that each pixel in the
>>>> original maps to 1.273 pixels on your screen. So some kind of
>>>> interpolation or nearest neighbour replacement has to be done, and
>>>> this makes text labels look bad. Other line work will look bad too.
>>>>    If you try and download more map tiles at a higher resolution then
>>>> you'll find the labels are now way too small, because what you've
>>>> downloaded are map tiles designed for a higher zoom level on a web
>>>> browser. Web map browsers have a fixed set of zoom values that
>>>> correspond to the resolution of the map tiles. With an R window, you
>>>> are free to choose odd zoom factors that give the ugly behaviour.
>>>>    If you can resize your R window exactly right then you might get
>>>> something that looks good!
>>>>    The alternative is to build a background map yourself from
>>>> OpenStreetMap *vector* data and some code and some styling. Or use a
>>>> map tile provider that doesn't have text labels and add them to
>>>> selected places with R graphics commands. Lines and polygons will
>>>> still be stretched and a bit "jaggy" but our eyes don't notice this as
>>>> much as badly scaled text.
>>>> Barry
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