[R-sig-Geo] UTM problem

[Sarah Goslee]

It looks like Uganda is mostly but not entirely in 36N. It's possible
the data switches zones, or that it keeps the same zone throughout
and uses northing and/or easting values outside the usual range.
Plotting the entire dataset as x, y coordinates would answer that
question very quickly.

Here's some more information:
http://commons.wikimedia.org/wiki/File:LA2-Africa-UTM-zones.png
http://en.wikipedia.org/wiki/Universal_Transverse_Mercator_coordinate_system

Sarah

On Wed, Oct 13, 2010 at 10:08 AM, Werner W. <pensterfuzzer at yahoo.de> wrote:
> Hi Sarah,
>
> many thanks for checking this. I looked at the documentation again and this is
> the info about the GPS receiver setting they used:
> POSITION FRMT: hddd.ddddd
> MAP DATUM: WGS 84
> CDI: +-0.25
> UNITS: METRIC
> HEADINGS: GRID E000
> DEGEES
>
>
> I'm not sure if this is any useful.
> Any idea what I should be looking for?
>
> The survey actually covers the whole of Uganda. Can it actually be that the
> entire country is UTM zone 36N or does the zone have to change? The docu
> suggests it is all 36N.
>
> Thanks again,
>  Werner
>
>
>
>
> ----- Ursprüngliche Mail ----
>> Von: Sarah Goslee <sarah.goslee at gmail.com>
>> An: Werner W. <pensterfuzzer at yahoo.de>
>> CC: r-sig-geo at stat.math.ethz.ch
>> Gesendet: Mittwoch, den 13. Oktober 2010, 14:48:50 Uhr
>> Betreff: Re: [R-sig-Geo] UTM problem
>>
>> Hi,
>>
>> I double-checked your results with an online conversion tool
>> (http://www.rcn.montana.edu/resources/tools/coordinates.aspx)
>> and got the  same answer.
>>
>> That means that your R code is fine, and there's  something
>> wrong with the original data. If possible, you should check  with
>> the source. There could be a problem with the metadata, or
>> with the  data themselves.
>>
>> Sarah
>>
>> On Wed, Oct 13, 2010 at 9:37 AM, Werner W.  <pensterfuzzer at yahoo.de>  wrote:
>> > Hi,
>> >
>> > this questions is not really about R but it  would be great if somebody
> could
>> > point me to a forum or so where I can  get help with this.
>> >
>> > I only know a few basics about GIS and have  a problem with some UTM
>>coordinates
>> > from a survey.
>> > Coordinates  are given as, e.g.
>> > 3258843     32780
>> > which are supposedly zone  36N on system WGS84 (according to the
>>documentation).
>> > If I convert it to  long/lat using gdal:
>> >> require(rgdal)
>> >> SP <-  SpatialPoints(cbind(X=3258843,  Y=32780),proj4string=CRS("+proj=utm
>> >>+zone=36  +ellps=WGS84"))
>> >> spTransform(SP, CRS("+proj=longlat +ellps=WGS84")) #  x1=longitude x2=lat
>> > SpatialPoints:
>> >           X         Y
>> >  [1,] 57.0489 0.2706471
>> > Coordinate Reference System (CRS) arguments:  +proj=longlat +ellps=WGS84
>> >
>> > The point should be close to Kampala  which has the coordinates 0.3°,
>>32.633333°
>> > and UTM 36N 459199 33160 on  WGS84. My data's easting seems quite off.
>> >
>> > Has anybody an idea  what I am doing wrongly?
>> >
>> > Thanks so much,
>> >   Werner
>> >
>> >

-- 
Sarah Goslee
http://www.functionaldiversity.org