Re: [R-sig-Geo] Elevation data

[Bacou, Melanie]

R raster::getData("SRTM", ...) will return elevation rasters at 90m 
resolution.

See:
https://www.rdocumentation.org/packages/raster/versions/2.5-8/topics/getData 


http://www.cgiar-csi.org/data/srtm-90m-digital-elevation-database-v4-1

--Mel.

On 1/11/2017 6:26 AM, Miluji Sb wrote:

Dear Michael,

Thank you for your reply and the suggestions.

Ideally, I would like a raster from which I can extract elevation at 1° x
1° resolution. I do not have much experience with working with DEM but have
work with data such as GPW.

I will definitely look at the datasets. Could you kindly suggest one that I
could convert to raster and extract? Hope that's not a silly question.

Sincerely,

Milu

On Wed, Jan 11, 2017 at 1:51 AM, Michael Sumner  wrote:


Passed through? Maybe you want ?raster::extract

There are a few versions of global elevation on CRAN, necessarily at low
resolution but no overall summary afaik (someone should do this :).

This is one: https://cloud.r-project.org/web/packages/GEOmap/index.html

If you have the stomach for development versions of packages see elevatr:
https://github.com/jhollist/elevatr

I tend to have the high-resolution files at hand because we use them
constantly, the main ones are Gebco14/Gebco08 and Etopo1/Etopo2 (from
Smith-Sandwell).

There's a reasonable overview here, you probably should find a specific
data set that is at the resolution you are after already, and you can cite
its derivation for your work:

http://vterrain.org/Elevation/global.html

Cheers, Mike.

On Wed, 11 Jan 2017 at 10:20 Miluji Sb  wrote:


Dear all.

Is there a way to download global elevation data at the 1° x 1° resolution
in R using a given set of coordinates?

I know about the getData() function but can many coordinates be passed
through this? Thanks!

Sincerely,

Milu

 [[alternative HTML version deleted]]

___
R-sig-Geo mailing list
R-sig-Geo@r-project.org
https://stat.ethz.ch/mailman/listinfo/r-sig-geo


University of Tasmania Electronic Communications Policy (December, 2014).
This email is confidential, and is for the intended recipient only.
Access, disclosure, copying, distribution, or reliance on any of it by
anyone outside the intended recipient organisation is prohibited and may be
a criminal offence. Please delete if obtained in error and email
confirmation to the sender. The views expressed in this email are not
necessarily the views of the University of Tasmania, unless clearly
intended otherwise.
.


--
Dr. Michael Sumner
Software and Database Engineer
Australian Antarctic Division
203 Channel Highway
Kingston Tasmania 7050 Australia



[[alternative HTML version deleted]]

___
R-sig-Geo mailing list
R-sig-Geo@r-project.org
https://stat.ethz.ch/mailman/listinfo/r-sig-geo


___
R-sig-Geo mailing list
R-sig-Geo@r-project.org
https://stat.ethz.ch/mailman/listinfo/r-sig-geo

Re: [R-sig-Geo] shortestPath in a loop

[Eric Carr]

Generically independent of R, A graph and the connectivity between points
needs defined before a shortest path algorithm can be applied.  If it
assumes all points are connected, than the shortest path will be a straight
line.  What you are looking for is some sort of  minimum spanning tree for
the vertices.
Eric

On Thu, Jan 12, 2017 at 11:17 AM, marta azores  wrote:

> Dear forum members,
>
> I would like to know how join several points with the aim to track a ship.
>
> After reading the documentation of some packages, I decided to use the
> function shortestPath, but I only got the line between the first and the
> last location of my points list. I need the complete survey, including also
> the middle points. I try a loop to build the survey of the boats using
> their locations, but It didn't work to me.
>
>
> Any idea?
>
> Thanks in advance,
>
> Marta
>
> #script# it's also attached in a R.file: question loop2.R
> ##
> #
> #raster# it's attached
> azoTS1<- raster("C:/Users/Documents/azoTS1.tif")#wgs84
> #
> #10 points# it's attached
> boat <- read.table("C:/Users/Documents/10pontos.csv", header=TRUE,
> sep=",", na.strings="NA", dec=".", strip.white=TRUE)#
> head(boat)
>
> #raster to transitionlayer
> trCostS4<- transition(1/azoTS1, mean, directions=4)
>
> # points to spatialpointsdataframe
> x=boat$Long1
> y=boat$Lat1
> coords = cbind(x, y)
> plot(coords)
> sp = SpatialPoints(coords, proj4string=CRS("+proj=longlat +ellps=WGS84
> +datum=WGS84"), bbox = NULL)
> sp
> spdf=SpatialPointsDataFrame(sp,boat)
> spdf
> nrow(spdf)
> plot(sp,axes=TRUE)
> plot(spdf,add=TRUE, axes=TRUE)
>
> #shortestpath
>
> ## 1) this script only join the first point of the list and the last one,
> and the points in the middle are not used.
> CostpathSPdf <- shortestPath(trCostS4, spdf[1,], spdf[10,],
> output="SpatialLines")
> plot(CostpathSPdf,add=TRUE,axes=TRUE,col=2)#R_plot1.png (it's attached)
>
> ## 2) this script didn't work to me
>
> #first way from website: http://stackoverflow.com/
> questions/8127066/loop-or-sapply-function-for-multiple-
> least-cost-analysis-in-r?answertab=active#tab-top
> for(i in 1:nrow(spdf)) {
>   # Computation
>   Costpath <- shortestPath(trCostS4, spdf[i,], spdf[10,],
> output="SpatialLines")
>   plot(Costpath)
>
> }
>
> #Error in validObject(.Object) :
> #invalid class “SpatialLines” object: bbox should never contain infinite
> values
>
> ___
> R-sig-Geo mailing list
> R-sig-Geo@r-project.org
> https://stat.ethz.ch/mailman/listinfo/r-sig-geo
>

[[alternative HTML version deleted]]

___
R-sig-Geo mailing list
R-sig-Geo@r-project.org
https://stat.ethz.ch/mailman/listinfo/r-sig-geo

Re: [R-sig-Geo] shortestPath in a loop

[Michael Sumner]

This seems impossible ( to get right, you can certainly get an answer)  in
general terms, do you really not know either an order of the points and/or
their relative spacing in time?

On Fri, Jan 13, 2017, 03:18 marta azores  wrote:

> Dear forum members,
>
> I would like to know how join several points with the aim to track a ship.
>
> After reading the documentation of some packages, I decided to use the
> function shortestPath, but I only got the line between the first and the
> last location of my points list. I need the complete survey, including also
> the middle points. I try a loop to build the survey of the boats using
> their locations, but It didn't work to me.
>
>
> Any idea?
>
> Thanks in advance,
>
> Marta
>
> #script# it's also attached in a R.file: question loop2.R
> ##
> #
> #raster# it's attached
> azoTS1<- raster("C:/Users/Documents/azoTS1.tif")#wgs84
> #
> #10 points# it's attached
> boat <- read.table("C:/Users/Documents/10pontos.csv", header=TRUE,
> sep=",", na.strings="NA", dec=".", strip.white=TRUE)#
> head(boat)
>
> #raster to transitionlayer
> trCostS4<- transition(1/azoTS1, mean, directions=4)
>
> # points to spatialpointsdataframe
> x=boat$Long1
> y=boat$Lat1
> coords = cbind(x, y)
> plot(coords)
> sp = SpatialPoints(coords, proj4string=CRS("+proj=longlat +ellps=WGS84
> +datum=WGS84"), bbox = NULL)
> sp
> spdf=SpatialPointsDataFrame(sp,boat)
> spdf
> nrow(spdf)
> plot(sp,axes=TRUE)
> plot(spdf,add=TRUE, axes=TRUE)
>
> #shortestpath
>
> ## 1) this script only join the first point of the list and the last one,
> and the points in the middle are not used.
> CostpathSPdf <- shortestPath(trCostS4, spdf[1,], spdf[10,],
> output="SpatialLines")
> plot(CostpathSPdf,add=TRUE,axes=TRUE,col=2)#R_plot1.png (it's attached)
>
> ## 2) this script didn't work to me
>
> #first way from website:
> http://stackoverflow.com/questions/8127066/loop-or-sapply-function-for-multiple-least-cost-analysis-in-r?answertab=active#tab-top
> for(i in 1:nrow(spdf)) {
>   # Computation
>   Costpath <- shortestPath(trCostS4, spdf[i,], spdf[10,],
> output="SpatialLines")
>   plot(Costpath)
>
> }
>
> #Error in validObject(.Object) :
> #invalid class “SpatialLines” object: bbox should never contain infinite
> values
> ___
> R-sig-Geo mailing list
> R-sig-Geo@r-project.org
> https://stat.ethz.ch/mailman/listinfo/r-sig-geo

-- 
Dr. Michael Sumner
Software and Database Engineer
Australian Antarctic Division
203 Channel Highway
Kingston Tasmania 7050 Australia

[[alternative HTML version deleted]]

___
R-sig-Geo mailing list
R-sig-Geo@r-project.org
https://stat.ethz.ch/mailman/listinfo/r-sig-geo

[R-sig-Geo] Difference in coordinates to country conversion

[Miluji Sb]

I have a set of coordinates at 1° x 1°  which look like this:

structure(list(longitude = c(-179L, -178L, -177L, -177L, -177L,
-176L), latitude = c(-15L, -15L, -14L, 51L, 52L, -22L)), .Names =
c("longitude",
"latitude"), row.names = c("1", "2", "3", "4", "5", "6"), class =
"data.frame")

I am trying to obtain country names for them and tried the following two
methods. There are some difference (mostly between USA and Canada). While
sometimes method 1 provides a country name but method 2 cannot.

Is there a way to say if either of the methods are more accurate? Or
another more accurate method? Or am I doing something wrong?

Thanks!

Sincerely,

Shouro

library(raster)
library(tmap)
library(rworldmap)
library(countrycode)

# Method 1

{
  countriesSP <- getMap(resolution='low')
  #countriesSP <- getMap(resolution='high') #you could use high res map
from rworldxtra if you were concerned about detail

  # convert our list of points to a SpatialPoints object

  # pointsSP = SpatialPoints(points, proj4string=CRS(" +proj=longlat
+ellps=WGS84 +datum=WGS84 +no_defs +towgs84=0,0,0"))

  #setting CRS directly to that from rworldmap
  pointsSP = SpatialPoints(coord_dams,
proj4string=CRS(proj4string(countriesSP)))


  # use 'over' to get indices of the Polygons object containing each point
  indices = over(pointsSP, countriesSP)

  # return the ADMIN names of each country
  indices$ADMIN
  #indices$ISO3 # returns the ISO3 code
  #indices$continent   # returns the continent (6 continent model)
  #indices$REGION   # returns the continent (7 continent model)
}

# Method 2
pts_dams <- SpatialPoints(coord_dams,proj4string=CRS(proj4string(worldmap)))
indices_dams <- over(pts_dams, worldmap,na.rm=TRUE)
indices <- cbind(indices_dams, coord_dams)

#Keep only ISO3, log, lat
foo_dams<-indices[,c(3,12,13)]

[[alternative HTML version deleted]]

___
R-sig-Geo mailing list
R-sig-Geo@r-project.org
https://stat.ethz.ch/mailman/listinfo/r-sig-geo