[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[McIDAS #QJI-536086]: Correction for MODIS bow-tie effect

Hi again Carolina,

After some more searching, I found that we still have a MODIS package on our
anonymous FTP server:

machine:   ftp.unidata.ucar.edu
user:      anonymous
pass:      address@hidden
directory: pub/mcidas/contrib
file:      modis_l1b.tar.gz

Here are the comments from a previous email about the code in this package:

 >I have been temporarily pulled away from the MODIS project to work on
 >another high priority project since May 2004. Even the latest version of
 >the MODIS remap software is more than one year old.  There were some
 >improvements being made to the software after I provided the decoders to

 >We implemented the polar Stereographic projection remapping
 >program for the granules over the north polar region for the 1KM res L1B
 >(MOD021KM, and MYD021KM); and added the calibration block to the
 >remapped McIDAS multi-band AREA. For the 500m and 250m resolution L1B
 >data, the remap programs are pretty the same as before.  As I mentioned
 >to Dave, the software is still under development and at its testing
 >stage. Currently, there is no document for the software.  For a general
 >description on how the MODIS granules are re-projected and how the
 >bow-tie effect is corrected, please see my previous e-mail to Dave Santek.


 >I also include the
 >Makefile for the two remapping decoders. I used the HDF library with in
 >the McIDAS package.

 >Again, the code is not fully developed.  Because some settings are hard
 >coded, the software will need to be modified before it can be run on
 >other system.


The e-mail to Dave Santek that Aiwu is referring to is (note the date):

  >>Hi, Dave,
  >>I have put the MODIS L1B HDF decoders on our anonymous ftp server
  >>(ftp://gp16.www.noaa.gov) under directory /pub/modis. The tar file
  >>includes 3 decoders for L1B data at 1KM, HKM, and QKM resolution, some
  >>driver scripts for the our local remapping processing, as well as 3
  >>sample AREA files at different resolutions and GIF images. I have
  >>written a short compile script for compiling the 3 decoders using HDF
  >>library within McIDAS. We will keep at least 3 days on the server.
  >>Currently, we only remap/correct L1B data from SSEC MODIS realtime
  >>system. This is mainly because SSEC provides data in a more timely
  >>manner and the granules are generally longer than 5-minutes. Our
  >>customers ( Fire analysis, OSEI ) prefers SSEC's data. The remapped
  >>region is limited to CONUS (22N-53N, 125W-65W). The code can be easily
  >>modified to apply to global data. The output AREA file is in
  >>Rectilinear projection. Passes over the polar region are skipped.
  >>The 3 remappers/decoders are logically very similar. Since the bow-tie
  >>effect is caused by the over sampling of multi-scans between adjacent
  >>frames, to get ride of it, one possible is to remap the pass. What I am
  >>doing in the decoders is to use geolocation at 1km to interpolate into
  >>500m and 250m for HKM and QKM data, grid the raw data into an array by
  >>embedding each pixel using its lat/lon. Since resolution gets lower as
  >>it approaches the edges, patchy edge problem arises after the gridding.
  >>To fix the the problem, simple 1-D interpolation, extrapolation,
  >>nearest neighborhood filling are used to fill the holes.  As you could
  >>image, it is quite CPU consuming. Base on our user's interest, only
  >>selected bands are remapped: 8 bands( 1-4,6,22,31) at 1KM, 4 bands(1-4)
  >>at HKM, and 2 bands(1-2) at QKM.
  >>The software is still under development. Although it is
  >>semi-operational on our system, you may still see certain bugs in the
  >>code. For example, in the remapped images, there are some navigation
  >>problem( appears as boundary off 2 pixels near the edges). The PS
  >>remap/decoders for 1km and hkm are almost done. Since this project is
  >>still at its preliminary stage,we have no documents yet.  To make the
  >>code more readable, I have taken out some debug statements, added some
  >>comment lines in the program. Attached are 2 sample images( Chesapeake
  >>Bay, and Albemarle Sound)  generated from 250m raw data and remapped
  >>I don't mind at all that the software to be used by others. 

So, this code may or may not be helpful.

Best of luck!


Unidata User Support                                    UCAR Unidata Program
(303) 497-8642                                                 P.O. Box 3000
address@hidden                                   Boulder, CO 80307
Unidata HomePage                       http://www.unidata.ucar.edu

Ticket Details
Ticket ID: QJI-536086
Department: Support McIDAS
Priority: Normal
Status: Closed

NOTE: All email exchanges with Unidata User Support are recorded in the Unidata inquiry tracking system and then made publicly available through the web. If you do not want to have your interactions made available in this way, you must let us know in each email you send to us.