comp.lang.idl-pvwave archive - RDF feed
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description: Messages from Usenet group comp.lang.idl-pvwave, compiled by Paulo Penteado
items: Re: Georeferencing satellite data in batch-mode ENVI?

Re: Georeferencing satellite data in batch-mode ENVI?
type: item
description: Hi, this is not a trivial task. It begins with reading the data from the HDF file. In case it's HDF5, I have attached a smal routine, READ_HDF, which can help you with that task. Once you have extracted your data and longitude and latitude arrays, you want to display them in a chosen projection. The classical routine for this task is IMAGEMAP by Liam Gumley: http://cimss.ssec.wisc.edu/~gumley/imagemap.html However, I once wrote my own routine based on IMAGEMAP (and a lot of ideas from Rene Preusker and Chris O'Dell) which gives you an object, named, well, MAP_IMAGE, which has the same features as IMAGEMAP and some more. It adds e.g. a colour bar (using David Fannings COLORBAR routine) and lets you choose any of the IDL built-in colour tables plus some more, including one for elevation data and one with blue colours for negative values and red colours for positive values, which is nice for difference plots. You can also choose to use a discrete colour bar. It also allows you to add multiple satellite overpasses or granules subsequently into the same projection. And, above all, it can create plots with black colour onto a white background! :-) The complete file is also attached below. All keywords accepted by MAP_SET are passed through via _EXTRA, e.g. LONDEL, LATDEL, or the projection types STEREO, SINUSOIDAL, etc. The file comes with some descriptions on top and some examples at the end, so I would be pleased if you gave it a try. Besides COLORBAR, it also uses a little routine WIN, which is an extension to the built-in WINDOW command. WIN just checks whether a chosen window already exists, thus avoiding destroying and creating the same window over and over again. Once you arranged the windows on the screen, they stay where they are. The file is also attached below. Now, assuming that the data is in HDF5 and that the appropriate datasets are named "data", "longitude" and "latitude", an IDL code fragment would look like this: <IDL> data = read_hdf(hdf_file, "data") l…
date: 2005-10-27T08:50:11-00:00

Re: Georeferencing satellite data in batch-mode ENVI?
type: item
description: Hi again, as promised, the files are now on a web server: http://wew.met.fu-berlin.de/idl/ I also added H5O_IS_GROUP, which is needed by READ_HDF. Cheers, Peter
date: 2005-10-27T09:24:29-00:00

Re: Georeferencing satellite data in batch-mode ENVI?
type: item
description: I did a similar task a while back by georeferencing hundreds of hypercubes. Only difference was I had to create the array of lats/lons, which was a task in itself. This array of lats/lons (or any geocoordinates) is the equivalent of an Internal Geometry Model (IGM). Since you have an IGM for each file, yes, you can simply create a Geographic Lookup Table (GLT) using ENVI_GLT_DOIT, then warp the image using the GLT with ENVI_GEOREF_FROM_GLT_DOIT. There will be a lot of logistics around getting the data out of the HDF file, assigning FIDs and such, but what's above is the heart of what's required. Ask back if you need more help... Chris
creator: cjengo
date: 2005-10-27T12:31:32-00:00

Re: Georeferencing satellite data in batch-mode ENVI?
type: item
description: Chris and Peter, Thanks a million for your help. I've got my code running now. I should note that I didn't use Liam's "imagemap" because of his strong caveat about the output maps not being quantitative; I have a lot of analysis to do on the mapped data. I have used imagemap (and will experiment with Peter's modification) for display and it is great. I appreciate your replies and thanks again. Barry
creator: Barry Lesht
date: 2005-10-27T14:42:48-00:00

Re: Georeferencing satellite data in batch-mode ENVI?
type: item
description: drdull wrote: > I've got a lot (thousands) of satellite images (HDF files) that I want > to georeference and project onto a standard grid. I want to automate > this using IDL/ENVI. Each input file includes the satellite sensor > data arrays as well as arrays with the earth location (latitude and > longitude)for each pixel. I'm interested in knowing if anyone has done > anything similar in batch mode and, if so, how you approached the > problem. Is it as simple as defining a projection, reading the data, > creating an "GLT" from the location data, and georeferencing to the new > GLT? Thanks. Can you tell us more about the satellite data? There may be a satellite-specific software package (non IDL) which would do the job more easily. Cheers, Liam. Practical IDL Programming http://www.gumley.com/
creator: liamgumley
date: 2005-10-27T18:58:19-00:00