Web Content Display

Web Content Display (CoastWatch User Forum)

The NOAA CoastWatch Forum provides information in several categories.  The information is relevant to CoastWatch products and software (https://coastwatch.noaa.gov)  and vary in technical details.  For questions and issues not addressed here,  start a thread in the appropriate category or contact the CoastWatch HelpDesk (coastwatch.info@noaa.gov).  Please note our Privacy Policy (https://www.noaa.gov/privacy.html) and that this is a public forum.  All information is voluntarily and anonymous submissions are accepted pending review prior to posting. 

Forums

Back

How to determine the pixel for a particular latitude and longitude value

RSS (Opens New Window)(Opens New Window)
MS
Michael Soracco, modified 4 Years ago.

How to determine the pixel for a particular latitude and longitude value

Youngling Posts: 39 Join Date: 8/11/16 Recent Posts

One question is how cwsample determines the relevant pixel for a particular latitude and longitude value? Is it capable of finding the pixel in which a lat/long value falls or is there some kind of nearest neighbor search built in? Also, is there any command-line approach for finding the nearest pixel with a value in case the queried GPS pixel falls on land/returns an NA (21.71,39.08,1365,4381)?

MS
Michael Soracco, modified 4 Years ago.

RE: How to determine the pixel for a particular latitude and longitude value

Youngling Posts: 39 Join Date: 8/11/16 Recent Posts

a script that handles this "nearest pixel with a value" issue for the user.  It also serves as an example script that you can edit and play with (Javascript-like syntax).  You run it as follows:

 

$ cwscript nearest.bsh -- inputFile variableName latitude longitude windowSize

 

where the window size is an odd number to search a 3x3 window, 5x5 window, etc.  Example use:

 

$ cwscript nearest.bsh -- OLCVCW.J2020140.161605.merc.hdf chlor_a 21.3109 -92.1415 5

Getting nearest value in chlor_a to (21.3109,-92.1415) within 5 pixel window

Nearest (row, column) = (3877,3004)

No valid value found at nearest coordinate, starting search

Searching within radius of 1 pixel(s) of nearest coordinate

Searching within radius of 2 pixel(s) of nearest coordinate

Search found a valid value at (row, column) = (3879,3002)

Distance is 0.8582845211163442 km from geographic location

Variable value is 0.07085878401994705

 

Note the double dash to protect the program from thinking that -92.1415 is an option argument.

cwscript nearest neighbor pixel location cwsample command line utility

Attachments: