Hi Tim, > I have a point shape containing field measurements in a small scale > studyarea. Unfortunately these points didn`t have geographic or projected coordinates. The spatial reference for these points are theodolite measurements. For four corner points gps measurements of projected coordinates are available. I want to georeference my point shape in these projected coordinate system and have no idea how. > Here is a subset of my data: > > x <- c(5.786, -3.766, -12.613, -21.836, -26.340, 3.958, -11.120, -17.266, > -18.938, > 16.751, -21.507, 26.420, -19.916, 23.184, 9.660, -5.711, -18.256, 27.888, > 12.634, -33.510) > y <- c(4.470, 0.797, -3.130, -7.656, -9.313, 8.700, 6.923, 8.545, 12.468, > 4.748, > -20.920, -5.396, -24.830, -11.636, 22.462, 19.210, -28.851, -9.510, 27.421, > 8.035) > z <- c(1100.493, 1100.867, 1101.798, 1102.559, 1103.703, 1102.366, 1107.249, > 1110.781, > 1113.920, 1096.967, 1095.284, 1088.956, 1092.869, 1086.786, 1101.300, > 1110.197, NA, NA, NA, NA) > gps_x <- c(NA,NA,NA,NA,NA,NA,NA,NA,NA,NA,NA,NA,NA,NA,NA,NA, 4560136, 4560184, > 4560172, 4560121) > gps_y <- c(NA,NA,NA,NA,NA,NA,NA,NA,NA,NA,NA,NA,NA,NA,NA,NA, 5289465, 5289482, > 5289521, 5289502) > > d <- data.frame(x,y,z,gps_x,gps_y) > d > coordinates(d) = ~x+y > plot(d, axes=T) > > gps_points <- d[17:20,] > points(gps_points, pch=19, col="red") > > Because both measurements - the theodolite values and the gps values - are > measured in meters, my > first idea was to calculate the coordinates for all points by sum the > difference between a gps > point and every single theodolite point in x- and y-direction. Unfortunately > there are little > differences depending which gps point is used as basis.
If you can assume the little differences being due to the error in gps-measurements, you could calculate your coordinates with all your gps points as a basis and then take the mean as final value. Tom > Is there a better way to transform the point pattern into the projected > coordinate system? > The proj4string for my coordinate system is: > +proj=tmerc +lat_0=0 +lon_0=12 +k=1 +x_0=4500000 +y_0=0 +ellps=bessel > +units=m +no_defs > > Thank you very much. > > TIM > > -- Technische Universität München Department für Pflanzenwissenschaften Lehrstuhl für Grünlandlehre Am Hochanger 1 85350 Freising / Germany Phone: ++49 (0)8161 715324 Fax: ++49 (0)8161 713243 email: tom.gottfr...@wzw.tum.de http://www.wzw.tum.de/gruenland _______________________________________________ R-sig-Geo mailing list R-sig-Geo@stat.math.ethz.ch https://stat.ethz.ch/mailman/listinfo/r-sig-geo
