Messages from Usenet group comp.lang.idl-pvwave, compiled by Paulo Penteado
Gautam Bisht (bishtgautam@yahoo.com) writes: > I am a new user of IDL and facing trouble trying to open MODIS images > and its products, which are in HDF and HDF EOS format. I am able to > see that ENVI can open those files but I want to write a code to > extract the values in those files. Could someone help me out with > this? maybe by pointing out some sources where I could get more info. Hopefully those MODIS files are in HDF5 format, so you can use the new H5_BROWSER function to look at them. If not (and the MODIS files I have hanging around here are not), then you will have to use the clunkier HDF_BROWSER to read them. The H5_BROWSER is slick and works the way I expect it to. (Did RSI write this!?) The HDF_BROWSER works too, but I always have to muck around with it to get what I want. (The boys who wrote this didn't take that class on GUI design, I guess.) If you can't get what you want that way, I found a file named MAS_READ on one of the MODIS web pages, which reads "a single band of MODIS Airborne Simulator (MAS) image data from a Level 1B HDF file". You can probably get the crux of the HDF matter from this file. It really is not too hard to figure it all out, at least if you start with a good example. Cheers, David -- David W. Fanning, Ph.D. Fanning Software Consulting, Inc. Phone: 970-221-0438, E-mail: david@dfanning.com Coyote's Guide to IDL Programming: http://www.dfanning.com/ Toll-Free IDL Book Orders: 1-888-461-0155
CIRA still has their HDF-EOS tip's page on-line ... http://www.cira.colostate.edu/special/csuidl/IDLEOS.htm Kelly Dean ATS/CSU Gautam Bisht wrote: > Hi all, > I am a new user of IDL and facing trouble trying to open MODIS images > and its products, which are in HDF and HDF EOS format. I am able to > see that ENVI can open those files but I want to write a code to > extract the values in those files. Could someone help me out with > this? maybe by pointing out some sources where I could get more info. > > Thanxs > Gautam >
On 15 May 2003 13:22:04 -0700, Gautam Bisht <bishtgautam@yahoo.com> wrote: > I am a new user of IDL and facing trouble trying to open MODIS images > and its products, which are in HDF and HDF EOS format. I am able to > see that ENVI can open those files but I want to write a code to > extract the values in those files. Could someone help me out with > this? maybe by pointing out some sources where I could get more info. geov3.pro ftp://g0dug03u.ecs.nasa.gov/data/modis/tools/hdf/geoview/geo v.pro ftp://g0dug03u.ecs.nasa.gov/data/modis/tools/hdf/geoview/geo v.pro http://hdfeos.gsfc.nasa.gov/hdfeos/platforminfo.cfm?ID=32&am p;swID=16 (these should be links to the same thing) This will let you create an image from L1B1KM, L1BHKM, or L1BQKM files. Its not easy to create the image unless you know the MODIS hdf format. Basically if you want a true color image you use either the L1B1KM or L1BHKM files, and pick bands 1, 4, and 3 (in that order, because they are appr. Red Green and Blue(or is it Red, Blue, Green?)) Note that band 1 is at 250 meter resolution, and bands 4 & 3 are both 500m resolution. There are different sds data sets for the different resolutions. (The higher resolution data-sets are included in the lower resolution hdf files, but they are aggregated to that resolution.) For example there is band 1(250 m resolution) data ine the L1BHKM (L1B half-kilometer(500m)) hdf file, but it is represented at the 500m resolution. This is why you need half or quarter resolution hdf files to get a true image. Anyways, the geov3.pro program is all readable IDL code so after you get it working you can browse thru the code, and see *how* it does what it does. There are other IDL programs available to read the basic data from L1A files. If you had a certain data set in mind I could point you in the right direction. Post back here if you have any questions. -- paul \ / wisehart >/ <//////$> |\|\|\ -- paul \ / wisehart >/ <//////$> |\|\|\
"Gautam Bisht" <bishtgautam@yahoo.com> wrote in message news:cf200650.0305151222.2959de38@posting.google.com... > I am a new user of IDL and facing trouble trying to open MODIS images > and its products, which are in HDF and HDF EOS format. I am able to > see that ENVI can open those files but I want to write a code to > extract the values in those files. Could someone help me out with > this? maybe by pointing out some sources where I could get more info. Which specific MODIS products are you trying to read? Cheers, Liam. Practical IDL Programming http://www.gumley.com/