comp.lang.idl-pvwave archive - RDF feed
type: channel
description: Messages from Usenet group comp.lang.idl-pvwave, compiled by Paulo Penteado
items: Re: Georeferencing Errors

Re: Georeferencing Errors
type: item
description: In article <ce4903f3.0411021020.112e251f@posting.google.com>, will.mccarty@msfc.nasa.gov (Will McCarty) wrote: > OK, I've posted on this before, and this time I'm using a bit of a > more common dataset (GTOPO30 terrain elevation), but getting similar > geolocation errors. Thus I'm interested in seeing what (if anything) > you guys can come up with. I use the following code: > > --test_lat_lon.pro > ulx = -99.99583333333334 > uly = 39.99583333333333 > dx = 0.00833333333333 > dy = 0.00833333333333 > > lat = fltarr(4800,6000) > lon = lat > for i = 0, 4799 do begin > for j = 0, 5999 do begin > lat[i,j] = uly - dy*j > lon[i,j] = ulx + dx*i > endfor > endfor I don't have the data set, but you might try ulx = -99.99583333333334D0 uly = 39.99583333333333D0 dx = 0.00833333333333D0 dy = 0.00833333333333D0 lat = DBLARR(4800,6000) As it is, you are not getting the precision you think you are. Or, it might be a pixel corner/center thing. Ken Bowman
creator: K. Bowman
date: 2004-11-02T20:07:37-00:00

Re: Georeferencing Errors
type: item
description: Will McCarty <will.mccarty@msfc.nasa.gov> wrote: > OK, I've posted on this before, and this time I'm using a bit of a > more common dataset (GTOPO30 terrain elevation), but getting similar > geolocation errors. Thus I'm interested in seeing what (if anything) > you guys can come up with. I use the following code: > > --test_lat_lon.pro > ulx = -99.99583333333334 > uly = 39.99583333333333 > dx = 0.00833333333333 > dy = 0.00833333333333 If you really care about that many significant figures, you need to declare these as doubles, not floats: IDL> dx = 0.00833333333333333333333333333 IDL> print,dx,format="(F25.21)" 0.008333333767950534821 IDL> dx = 0.00833333333333333333333333333d IDL> print,dx,format="(F25.21)" 0.008333333333333333218 - Marshall
creator: mperrin+news
date: 2004-11-02T20:57:45-00:00

Re: Georeferencing Errors
type: item
description: Will McCarty writes: > lat = fltarr(4800,6000) > lon = lat > for i = 0, 4799 do begin > for j = 0, 5999 do begin > lat[i,j] = uly - dy*j > lon[i,j] = ulx + dx*i > endfor > endfor Those other guys probably solved your problems, but I would have another look at the Dimension Juggling Tutorial unless you *like* sitting around for hours drinking coffee. :-) http://www.dfanning.com/tips/rebin_magic.html Cheers, David -- David W. Fanning, Ph.D. Fanning Software Consulting, Inc. Coyote's Guide to IDL Programming: http:/www.dfanning.com/ Phone: 970-221-0438, IDL Book Orders: 1-888-461-0155
creator: David Fanning
date: 2004-11-02T21:06:18-00:00

Re: Georeferencing Errors
type: item
description: The FOR FOR...ENDFOR ENDFOR will allow you to drink some coffee, but the MAP_PATCH operation with this image will allow you to get a tennis match in. IDL's PolyWarp and Poly_2D will get the remapping done in minutes. Kelly Dean Colorado State University Fort Collins, Colorado David Fanning wrote: > Will McCarty writes: > >> lat = fltarr(4800,6000) >> lon = lat >> for i = 0, 4799 do begin >> for j = 0, 5999 do begin >> lat[i,j] = uly - dy*j >> lon[i,j] = ulx + dx*i >> endfor >> endfor > > Those other guys probably solved your problems, > but I would have another look at the Dimension > Juggling Tutorial unless you *like* sitting > around for hours drinking coffee. :-) > > http://www.dfanning.com/tips/rebin_magic.html > > Cheers, > > David > -- > David W. Fanning, Ph.D. > Fanning Software Consulting, Inc. > Coyote's Guide to IDL Programming: http:/www.dfanning.com/ > Phone: 970-221-0438, IDL Book Orders: 1-888-461-0155
creator: Kelly Dean
date: 2004-11-04T05:31:59-00:00