[R-sig-Geo] Timezone boundaries (for adding to world map)?

[Roger Bivand]

On Wed, 18 Feb 2009, Greg Snow wrote:

> There is a shapefile (works well with maptools and sp packages) with a 
> world map and time zone information at: 
> http://openmap.bbn.com/data/shape/timezone/
>
> It has the info needed to color the countries or parts of countries 
> based on time zone, but does not have polygons for time zone stripes 
> over the oceans.

In fact, this shapefile provoked an update in sp, because it is really 
buggy. There are straight-line polygons and many others have multiple 
repeated coordinates (the sp update fixes these to retain finite label 
points), but it doesn't fix the absence of most of the data (several DBF 
columns are empty - checked in oocalc):

> library(rgdal)
> tz <- readOGR(".", "WrldTZA")
OGR data source with driver: ESRI Shapefile
Source: ".", layer: "WrldTZA"
with  1890  rows and  11  columns
Feature type: wkbPolygon with 2 dimensions
Warning messages:
1: In Polygon(cbind(jG[[1]], jG[[2]])) :
   Non-finite label point detected and replaced
2: In Polygon(cbind(jG[[1]], jG[[2]])) :
   Non-finite label point detected and replaced
3: In Polygon(cbind(jG[[1]], jG[[2]])) :
   Non-finite label point detected and replaced
> names(tz)
  [1] "FIPS"     "NAME"     "COMMENTS" "REGION"   "LAT"      "LON"
  [7] "TZ"       "GMTOFF"   "LOCALSUM" "OFFSET"   "CLASSES"
> summary(tz$GMTOFF)
NA's
1890
> summary(tz$TZ)
NA's
1890
> summary(tz$OFFSET)
         0     \xff0        -1    \xff-1    \xff+1       -10       +10
        25        57        13         7       181        24        38
   \xff+10     +10.5       +11     +11.5       +12   \xff+12        +2
        24         1        19         3        12        13         1
    \xff-2    \xff+2        +3    \xff-3    \xff+3      -3.5  \xff+3.5
         4        90        59       146        25         7         3
        -4        +4    \xff-4    \xff+4  \xff+4.5        -5        +5
        56         4       165         8         1       130        13
    \xff-5    \xff+5  \xff+5.5 \xff+5.75        -6        +6    \xff-6
        12         3        16         1        77        10        16
    \xff+6  \xff+6.5        -7        +7    \xff+7        -8        +8
        12        15        63        98        14        61        68
    \xff-8    \xff+8        -9        +9    \xff+9      +9.5      NA's
         3        56        82        97        13        11        33

where my locale is UTF-8.

I wrote to Martin offline that a more recent link is:

http://efele.net/maps/tz/world/

and I've put tz_world.rda on http://spatial.nhh.no/R/etc, but it is not 
line generalised, so it is very large and takes a long time to display - 
they've kept a lot of boundary detail.

Because TZ follow administrative boundaries, they are actually hard to do 
right. Maybe a raster version might help more if vector precision isn't 
needed?

Roger

>
> Hope this helps,
>
>

-- 
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: Roger.Bivand at nhh.no