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Re: how to get pixel data corresponding to some coordinates' points? [message #56222 is a reply to message #56214]

Sat, 13 October 2007 18:22

Jean H.
Messages: 472
Registered: July 2006

Senior Member

highstone wrote:
> On Oct 14, 1:21 am, "Jean H." <jghas...@DELTHIS.ucalgary.ANDTHIS.ca>
> wrote:
>> highstone wrote:
>>> I have a point vector file(.shp) containing a lot of weather
>>> stations, how can I get corresponding pixel data from a '.img' file
>>> with least works? 3q!
>> if you have envi too, you can use envi_convert_file_coordinates
>>
>> Jean
> to Jean,
> I look up the help of ENVI, find the role of
> "envi_convert_file_coordinates" is to "Use this procedure to convert
> x,y pixel coordinates to their corresponding map coordinates".

"and vice-versa"
By pixel coordinate, they mean the row and column number, by map
coordinate, they mean the geographical coordinate (lat-long or else)

Maybe I
> didn't have said clearly. My vector file and raster file had the same
> coordinates, what I want to get is the pixels' data corresponding to
> these points in vector file as soon as possible.so I don't know why to
> use this procedure?
> please forgive me for my poor knowledge,3q.

Yes, the idea is, if you want to program it (maybe there is a built-in
tool... I don't know... ArcGis has one for sure):
1)open your shape file
2)get the coordinates (let's say, lat-long) of each point in an array
3)open your image to gets its FID
4)call envi_convert_file_coordinates, fid, X,Y, lat,long (with NO
keyword), which will change your lat-long to the corresponding pixel row
and column on your image
5)extract the pixels values, using image[X,Y]

the help file for envi's function is terrible and often needs a few
dozen reading before to get the code working well!

Jean

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[Message index]

		Re: how to get pixel data corresponding to some coordinates' points? By: fanxing_gis on Mon, 15 October 2007 07:48
		Re: how to get pixel data corresponding to some coordinates' points? By: d.poreh on Mon, 15 October 2007 00:04
		Re: how to get pixel data corresponding to some coordinates' points? By: Jean H. on Sat, 13 October 2007 18:22
		Re: how to get pixel data corresponding to some coordinates' points? By: highstone on Sat, 13 October 2007 18:03
		Re: how to get pixel data corresponding to some coordinates' points? By: Jean H. on Sat, 13 October 2007 10:21

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