| Using map projections to display images [message #12613] |
Mon, 24 August 1998 00:00  |
seanr
Messages: 10
Registered: August 1998
|
Junior Member |
|
|
I'm trying to take digital air photo data with a known ground sample distance
resolution and a single georeference point (taken from a GPS receiver) and
display it in an arbitrary map projection. I have looked at the documentation
for MAP_SET, MAP_IMAGE, and MAP_PATCH. Using the example provided in the
documentation of MAP_PATCH, I have managed to get the image to come up in the
right projection, but I am unsure how to keep the resolution of the image the
same.
Does anyone have a good example to display an image warped to an arbitrary map
projection? (perfered projection would be transverse mercator)
Thanks in advance for any replys,
Sean
------------------------------------------------------------ ----------
Sean P. Rumelhart Positive Systems, Inc.
seanr@possys.com 250 Second St. East
PH: 406.862.7745 Whitefish MT 59937
FAX: 406.862.7759 www.possys.com
------------------------------------------------------------ ----------
-----== Posted via Deja News, The Leader in Internet Discussion ==-----
http://www.dejanews.com/rg_mkgrp.xp Create Your Own Free Member Forum
|
|
|
|
| Re: Using map projections to display images [message #12692 is a reply to message #12613] |
Wed, 02 September 1998 00:00  |
Erard
Messages: 11
Registered: November 1997
|
Junior Member |
|
|
In article <6s6l44$mf1$1@nnrp1.dejanews.com>, seanr@possys.com wrote:
> Well, for those who have been following this thread, I have been playing with
> MAP_SET and MAP_IMAGE and feel that I understand them much better now. I have
> discovered a way to keep the resolution of my imagery *almost* the same.
> Basically, MAP_SET will create a window of a default size if one does not
> exist, and MAP_IMAGE will place the image warped to the selected projection
> within that window...in a best fit. So, I set things up so that the window
> size = image size of the raw image. (I will have to use tiling on my full
> implementation anyway, so having a small window to put this all to is no big
> deal, I will probably use a pixmap window, or possibly the z-buffer). Here is
> a small snippet of my test code that will place the sub image in the map
> projection and keep it at the correct resolution:
>
I'm not sure the following answers your problem, but here is a small
procedure to simplify superpositions of images and maps. It works correctly
for Mercator and cylindrical projection with Map_set 1.33 (shipped with IDL
4), and haldles PS output correctly. Just forget the prep_map function, it
just corrects a personal problem I had with map_set.
pro TVmap, image, _extra=pipo, Ps=ps, grid=grid, label=label,
position=position,$
limit=limit
; ====================================================
; Superimpose a map to an image.
;
; Les limitse sont souvent d�cal�es d'1 pixel, probl�me d'arrrondi
; (d�pend du syst�me)...
; ====================================================
; Il faut intercepter les mots-clefs � tester, et ils ne sont alors plus
dans _extra
if keyword_set(position) then begin
message, /continue, 'Keyword POSITION no allowed (automatic)'
return
endif
if n_elements(grid) eq 0 then grid=1 ; defaut is ON
if n_elements(label) eq 0 then label=1
; Limit is adjusted if provided as a 4-elt vector.
; Otherwise, map_set defaults are used
If n_elements(limit) eq 4 then begin prep_map, latcent, longcent, limit,
_extra=pipo
endif else latcent=(longcent=(limit=0))
sz=size(image)
Xscreen=sz(1) + 40. ; d�calages pour mise en page
Yscreen=sz(2) + 80.
!P.font=-1
th=1
if keyword_set(ps) then begin
OldDevice = !D.name
set_plot,'ps'
!P.font=0
; coefPS=!D.x_px_cm/40. ;image � la m�me taille que sur l'�cran
coefPS=min([!D.X_vsize/Xscreen,!D.Y_vsize/Yscreen]) ;image sur toute la feuille
addPS=0.
device,filename='TVmap.ps',/color,bits=8,/landscape,/Bold
th=2
endif else begin
window, /free, xsize=Xscreen, ysize=Yscreen
coefPS=1.
addPS=1.
endelse
px0 = 20. ; small shift for page layout
py0 = 20.
;print, sz, coefPS, !D.x_vsize,!D.y_vsize
; Back to normal coordinates for Map_set
; adjust for odd and even dimensions (frame is always suposed to be
inside image)
qx=[px0,px0+sz(1)-(sz(1) mod 2)]*coefPS/(!D.X_vsize+addPS)
qy=[py0,py0+sz(2)-(sz(2) mod 2)]*coefPS/(!D.Y_vsize+addPS)
tv, image, px0*coefPS,py0*coefPS,xsize=sz(1)*coefPS, ysize=sz(2)*coefPS
;print, qx, qy
del=(qx(1)-qx(0))*0.01 ; Compensate a small dilatation of limits
qx(0)=qx(0)-del ; performed in MAP_SET with a similar dilatation
qx(1)=qx(1)+del ; of the plotting area.
del=(qy(1)-qy(0))*0.01
qy(0)=qy(0)-del
qy(1)=qy(1)+del
print, latcent, longcent
print, limit
map_set,latcent, longcent ,grid=grid, limit=limit,/noerase, label=label,$
londel=30.,latdel=30.,position=[qx(0),qy(0),qx(1),qy(1)],$
glinethick=th, _extra=pipo
; Ici, il faut tester la condition de sortie de Map_set et continuer en cas
d'erreur
!P.font=-1
if keyword_set(ps) then begin
device,/close
Set_Plot, OldDevice
endif
end
--
St�phane Erard
Institut d'Astrophysique Spatiale
Orsay, France
www.ias.fr/cdp
erard@ias.fr
|
|
|
|
|
|
| Re: Using map projections to display images [message #12708 is a reply to message #12613] |
Fri, 28 August 1998 00:00 |
Paul van Delst
Messages: 364
Registered: March 1997
|
Senior Member |
|
|
I notice that Liam Gumley has already replied to this question and it's probably
a bit incestuous (Liam works just down the hall) but I have to recommend his
IMAGEMAP.PRO (http://cimss.ssec.wisc.edu/~gumley/imagemap.html) procedure. For
me, and others here at CIMSS, it has made displaying satellite imagery in any
projection a no-brainer. He has also made changes recently to overlay multiple
images also so you can display more than one orbit of satellite data without
stringing all the input data into one huge array and then displaying that
(although I don't think that version is available on his webpage yet).
That's all.
paulv
seanr@possys.com wrote:
> UPDATE:
>
> Well, for those who have been following this thread, I have been playing with
> MAP_SET and MAP_IMAGE and feel that I understand them much better now. I have
> discovered a way to keep the resolution of my imagery *almost* the same.
> Basically, MAP_SET will create a window of a default size if one does not
> exist, and MAP_IMAGE will place the image warped to the selected projection
> within that window...in a best fit. So, I set things up so that the window
> size = image size of the raw image. (I will have to use tiling on my full
> implementation anyway, so having a small window to put this all to is no big
> deal, I will probably use a pixmap window, or possibly the z-buffer). Here is
> a small snippet of my test code that will place the sub image in the map
> projection and keep it at the correct resolution:
>
<code snippet snipped>
> For my limited example, this works like a charm.
>
> The one remaining problem I have is sometimes I can get a resulting image
> back that is 187 by 125 or some such, usually only a pizel or two. What I
> would like and have looked into a little is for MAP_SET and MAP_IMAGE to use
> xsize and ysize values as passed in, and not the window size. Has anyone
> attempted to do this, or should I go ahead and make my own?
--
Paul van Delst
Space Science and Engineering Center "Religious and cultural
University of Wisconsin-Madison purity is a fundamentalist
1225 W. Dayton St., Madison WI 53706 fantasy"
Ph/Fax: (608) 265-5357, 262-5974 V.S. Naipaul
Email: paul.vandelst@ssec.wisc.edu
Web: http://airs2.ssec.wisc.edu/~paulv
|
|
|
|
| Re: Using map projections to display images [message #12710 is a reply to message #12613] |
Fri, 28 August 1998 00:00 |
seanr
Messages: 10
Registered: August 1998
|
Junior Member |
|
|
UPDATE:
Well, for those who have been following this thread, I have been playing with
MAP_SET and MAP_IMAGE and feel that I understand them much better now. I have
discovered a way to keep the resolution of my imagery *almost* the same.
Basically, MAP_SET will create a window of a default size if one does not
exist, and MAP_IMAGE will place the image warped to the selected projection
within that window...in a best fit. So, I set things up so that the window
size = image size of the raw image. (I will have to use tiling on my full
implementation anyway, so having a small window to put this all to is no big
deal, I will probably use a pixmap window, or possibly the z-buffer). Here is
a small snippet of my test code that will place the sub image in the map
projection and keep it at the correct resolution:
image = bytarr(188,124)
openu, lun,'image.dat', /get_lun
readu,lun, IMAGE
close, lun
free_lun, lun
window, 0, xsize =188, ysize =124
TV, IMAGE ;Display the image so we can see what it looks like before warping.
pi = 3.1415925 LL_rad = 1.268 * 2.D * !pi / 360.D degfix = 1.0 /
double(cos(LL_rad)) ; Earth radius = 6378.17km ==> 111.32km/degree ; of
longitude at the equator, or 0.0089 deg/km ; xdegpkm = .00899D * degfix ;
fix size of longitudinal mile based on ; ydegpkm = .00899D ; cosine of
latitude x_mpdeg = double(111320.0 * degfix) y_mpdeg = double(111320.0)
;(image is approx .25 meters per pixel)
Minlon = double(-71.829 - ((94.0 *.25)/x_mpdeg)) ;71.829 lon W for center
pixel
Maxlon = double(-71.829 + ((94.0 *.25)/x_mpdeg))
Minlat = double(1.268 - ((62.0 * .25) / y_mpdeg)) ;1.268 lat N for center
pixel
Maxlat = double(1.268 + ((62.0 * .25) / y_mpdeg))
limit1 = [minlat, minlon, maxlat, maxlon]
loncenter = double(-71.829)
window, 1, xsize =188, ysize =124
MAP_SET, 0, loncenter, 0, /TRANSVERSE, limit=limit1, /noborder, xmargin=[0,0],
ymargin=[0,0]
result=MAP_IMAGE(image,startx,starty,xsize,ysize,$
latmin=limit1(0),latmax=limit1(2),$
lonmin=limit1(1),lonmax=limit1(3),$
compress=1)
tv,result,0,0 ;Display the warped image on the map at the proper position.
For my limited example, this works like a charm.
The one remaining problem I have is sometimes I can get a resulting image
back that is 187 by 125 or some such, usually only a pizel or two. What I
would like and have looked into a little is for MAP_SET and MAP_IMAGE to use
xsize and ysize values as passed in, and not the window size. Has anyone
attempted to do this, or should I go ahead and make my own?
------------------------------------------------------------ ----------
Sean P. Rumelhart Positive Systems, Inc.
seanr@possys.com 250 Second St. East
PH: 406.862.7745 Whitefish MT 59937
FAX: 406.862.7759 www.possys.com
------------------------------------------------------------ ----------
-----== Posted via Deja News, The Leader in Internet Discussion ==-----
http://www.dejanews.com/rg_mkgrp.xp Create Your Own Free Member Forum
|
|
|
|
comp.lang.idl-pvwave archive
Members
Search
Help
Login
Home
