[R-sig-Geo] Save plot as Geotiff

[Arnaud Mosnier]

Better late than never.
Thanks Roger !

Arnaud

2018-02-07 13:58 GMT-05:00 Roger Bivand <Roger.Bivand at nhh.no>:

> On Wed, 7 Feb 2018, Barry Rowlingson wrote:
>
> I'd do this by saving the image on the graphics device as a PNG, then
>> creating a "world" file (with extension PNGW) from the coordinates of the
>> corners and the resolution of the PNG. This is a six line text file with
>> sufficient information to georeference a grid. That's enough for `gdal` to
>> understand it, and then the `gdal` utilities can convert it to a GeoTIFF
>> (or load into R using `raster` and then save as a GeoTIFF).
>>
>> The tricky bit might be finding the corner coordinates of the graphics
>> device image. This is complicated by R leaving space for margins, or not
>> using your coordinate system.
>>
>
> Right - see the example in ASDAR 1st edition, chapter 4 chunks 42-44 in
>
> http://www.asdar-book.org/data.php?chapter=3 (zero-based php)
>
> which has par(mar=c(0,0,0,0), xaxs="i", yaxs="i") and widths and heights
> from maptools::GE_SpatialGrid().
>
> Roger
>
>
>
>> If this is a base graphics plot using the coordinate system units then you
>> can probably get them via some combination of the par() values, or you
>> might have set the margins to zero and that gives you the corners from
>> par()$usr (I think).
>>
>> If its grid graphics (like spplot) then.... uhhh. someone else probably
>> knows how to do it.
>>
>> Barry
>>
>>
>> On Wed, Feb 7, 2018 at 3:07 PM, Arnaud Mosnier <a.mosnier at gmail.com>
>> wrote:
>>
>> Hi,
>>>
>>> Long version:
>>> I made a plot (a map) including SpatialPolygons representing the coast of
>>> my region of interest, and a SpatialPointsDataframe representing
>>> locations
>>> of cities, and I want to save this map in GeoTiff format to allow other
>>> people to use this map as a georeferenced background without having to
>>> manage the various data sources. Is there a package/function in R that
>>> would allow me to do that?
>>> Note that converting the Spatial* objects to the raster format is not an
>>> option because I want to be able to see the names of the cities on the
>>> map.
>>>
>>>
>>> In short:
>>> Is there a way to save a plot composed of Spatial* elements in a GeoTiff
>>> format?
>>>
>>> Thanks
>>>
>>> Arnaud
>>>
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>>>
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>>>
>>>
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>>
> --
> Roger Bivand
> Department of Economics, Norwegian School of Economics,
> Helleveien 30, N-5045 Bergen, Norway.
> voice: +47 55 95 93 55; e-mail: Roger.Bivand at nhh.no
> http://orcid.org/0000-0003-2392-6140
> https://scholar.google.no/citations?user=AWeghB0AAAAJ&hl=en
>

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