Dear sir,
My data has been acquired from ENVI 4.0 and it has the following information
regarding pixel size and projection system:
samples = 596lines = 440bands = 21
pixel size: 4.710294*4.70871
file type = ENVI Standard
header offset = 0
map info = {UTM, 1.000, 1.000, 564761.521, 5699816.363, 4.7102936126e+000,
4.7087100663e+000, 31, North, WGS-84, units=Meters}
vitotagprojectionsystem = Universal_Transverse_Mercatorvitotagprojectiondatum =
WGS_84vitotagprojectionzone = 31
I was mistaken earlier that projection datum was Eueropean1950 instead it is
WGS84
so I think the projection code should be:
proj4string(A) <- CRS("+proj=utm +zone=31 +ellps=WGS84")
Regarding the tolerance problem;
The difference in the X coordinates (column 1 out of 21 column)varies from
4.7019876 to 4.719234 so the default tolerance 0.00212314227724164 does not
incorporate those variation.
This is my source of error.
Thanking you in advance
Pujan
> Date: Fri, 2 May 2008 19:49:07 +0200> From: [EMAIL PROTECTED]> To: [EMAIL
> PROTECTED]> CC: r-sig-geo@stat.math.ethz.ch> Subject: RE: [R-sig-Geo] Scale
> Bar> > On Fri, 2 May 2008, PUJAN RAJ REGMI wrote:> > >> >> > Dear list,> >
> Thanks to Mr. Roger, I have now able to plot my data using image and sp > >
> packages. Everything now seems ok for one type of data set where X and Y > >
> coordinates are regularly spaced with tolerance less than 0.000002. Now > > I
> tried to plot with another data set then soon I realize that X > >
> coordinates have tolerance about 0.02. This thing I realize when I get > >
> the error message as follows: ?gridded(A)<- TRUE suggested tolerance > >
> minimum: 0.00212314227724164Error in points2grid(points, tolerance) : > >
> dimension 1 : coordinate intervals are not constant? Then I tried to use > >
> points2grid to overcome this problem but it did not work.> > Do you know
> where the irregular values came from - type of file written by > what
> software? Are !
they just rounding at some stage - I feel that it would > be helpful to rule
out real causes before correcting something that might > be an actual mistake,
if you see what I mean.> > >> > One more question my data has a projection
system UTM (European1950) ZONE31.> > How can I incorporate this information
while converting spatial data?> > proj4string(A) <- CRS("+proj=utm +zone=31
+ellps=intl")> > but because ED50 is not well defined, there is no +towgs84=
value in the > EPSG database in the rgdal package. If you need to
datum-transform spatial > data (not the grid, obviously), you'll need the
+towgs84 values for your > location.> > Roger> > > Thanking you> > Pujan> >> >>
Date: Fri, 2 May 2008 11:29:37 +0200> From: [EMAIL PROTECTED]> To: [EMAIL
PROTECTED]> CC: r-sig-geo@stat.math.ethz.ch> Subject: Re: [R-sig-Geo] Scale
Bar> > On Thu, 1 May 2008, PUJAN RAJ REGMI wrote:> > > Dear,> > > I followed
the instruction given by Roger. But i got the following error > > message!
; coordinates(A) <- c("x", "y")> gridded(A) <- TRUE> > > greenchannel<
-matrix(A[,3],nrow=155,ncol=191,byrow=TRUE)Error in > > as.vector(x, mode) :
cannot coerce to > >
vectorredchannel<-matrix(A[,4],nrow=155,ncol=191,byrow=TRUE)Error in > >
as.vector(x, mode) : cannot coerce to vector> > >
nearinfraredchannel<-matrix(A[,5],nrow=155,ncol=191,byrow=TRUE)Error in > >
`[.data.frame`([EMAIL PROTECTED], i, j, ..., drop = FALSE) : undefined columns
> > selected> > >
midinfraredchannel<-matrix(A[,6],nrow=155,ncol=191,byrow=TRUE)Error in > >
`[.data.frame`([EMAIL PROTECTED], i, j, ..., drop = FALSE) : undefined columns
> > selectedThe image plot was black background with x and y axis values.> >
You are not reading what is being sent to you carefully enough, but at > least
this is a fresh thread, so some progress. Above, you have mixed up > my answer
with your own attempt to use rimage classes and functions. If > you have
spatial data, use spatial classes and functions, which permit > integration
with other spatial data.> > Using the data you sent me offline (but *.rar compr!
essed, please use gzip > or zip, rar is not portable), I have:> > > A <-
read.table("test.txt", skip=8, header=FALSE)> names(A) <- c("x", "y",
"greenchannel", "redchannel",> "nearinfraredchannel", "midinfraredchannel")>
coordinates(A) <- c("x", "y")> gridded(A) <- TRUE> > I note that you have not
given the projection of your data (UTM?), so > registering this data with other
data (stream channel patterns?) is not > made any easier.> > A$red <-
as.double(A$nearinfraredchannel)> A$green <- as.double(A$redchannel)> A$blue <-
as.double(A$greenchannel)> summary(A)> > The values appear to be in the 0-255
range, but do not go much beyond > halfway - do they need stretching?
Muliplying the values by 1.79 -> 1/(max(c(A$red, A$green, A$blue))/255) rounded
down a touch - gave a more > pleasing image, but I don't know the origins of
your data.> > image(A, red="red", green="green", blue="blue", axes=TRUE)> >
which shows the majority of your study area as 0 coded black, and the > remaind!
er is not very differentiated. It ought to be possible to code > these
0 values as NA, but currently the underlying method in sp does not > handle
NAs gracefully for rgb input - this will be improved in the next > release. So,
we recode 0 as 255 to get white:> > A$red <- ifelse(A$red < 1, 255, A$red)>
A$green <- ifelse(A$green < 1, 255, A$green)> A$blue <- ifelse(A$blue < 1, 255,
A$blue)> image(A, red="red", green="green", blue="blue", axes=TRUE)> > So now
to your scale bar:> > SpatialPolygonsRescale(layout.scale.bar(), offset =
c(566500, 5698000),> scale = 500, fill=c("transparent","black"),
plot.grid=FALSE)> text(566500, 5698075, "0", cex=0.7)> text(567000, 5698075,
"500 m", cex=0.7)> > You can complete the north arrow in the same way using
examples on the > help page for spplot, if you really want one.> > Finally, as
a geographer, I would point out that the scale bar and north > arrow are not
needed when the axes show the scale and the direction of > north. Anyone who
tells you that they have to be there (your supervisor?), > should read up!
on analytical graphics - extra details distract attention > from what the
data are saying. Probably using grid() is less intrusive, > and gives good
placing control across the whole graphic. When was the last > time anyone
actually used a map scale bar to read off distances from a > map?> > Roger> > >
> Any help?> > Thanking you> > Pujan> >
_________________________________________________________________> > Back to
work after baby?how do you know when you?re ready?> >> >
5797498&ocid=T067MSN40A0701A> > [[alternative HTML version deleted]]> >> >> >
-- > 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:
[EMAIL PROTECTED]> >
_________________________________________________________________> > Get Free
(PRODUCT) RED? Emoticons, Winks and Display Pics> >
http://joinred.spaces.live.com?ocid=TXT_HMTG_prodredemo!
ticons_052008> > -- > Roger Bivand> Economic Geography Section, Depart
ment 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: [EMAIL PROTECTED]
_________________________________________________________________
esh_messenger_052008
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