Dear Miltinho, You might want to take a look at this website:
http://spatialreference.org/ref/epsg/?search=SAD69 It allows you to export an existing coordinate system into a proj4 string, e.g.: Proj4js.defs["EPSG:29170"] = "+proj=utm +zone=20 +ellps=aust_SA +units=m +no_defs "; This you can then edit this by hand, e.g. to modify the datum: "+proj=utm +zone=20 +ellps=aust_SA +towgs84=-57,1,-41 +units=m +no_defs " cheers, Tom Hengl http://spatial-analyst.net PS: please be careful when using the spatialreference.org website - I discovered that the proj4 string often does not completely correspond to the CRS in use. -----Original Message----- From: [EMAIL PROTECTED] on behalf of milton ruser Sent: Tue 9/2/2008 8:04 PM To: [email protected] Subject: [R-sig-Geo] Utm to latlong conversion (Datum problem) Dear all, I know that it is a knew issue, but I have some troubles on the conversion of UTM to Latlong of my shape file. In fact, it apears to work but my input file is on South America Datum (SAD69), but I can´t find the how to indicate the datum. I tryed to include "+datum=SAD69" on the proj4string, but I received the following error: "unknown elliptical parameter name" Any help are welcome. Best wishes, miltinho astronaura brazil ------------- require(sp) require(maptools) require(rgdal) setwd("G:\\HDExt\\R_scripts_genericos\\converte_utm_latlong") SP<-readShapePoly("area_infl_ind.shp", IDvar=NULL, proj4string=CRS("+proj=utm +zone=22 +units=m +south")) SPll<-spTransform(SP, CRS("+proj=longlat +datum=WGS84")) [[alternative HTML version deleted]] [[alternative HTML version deleted]]
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