[R-sig-Geo] UTM problem
Sarah Goslee
sarah.goslee at gmail.com
Wed Oct 13 16:24:50 CEST 2010
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
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