Parent Topic: Supported File Formats

SeaWIFS CEOS

The GeoGateway library supports the OrbImage distributed SeaWIFS CEOS format for read access. Orbital Image is the commercial data provider of imagery from the ORBVIEW-2 (SeaWIFS) satellite. This translator was written using example level 1B, and 2A datasets provided by OrbImage. At this time level 2B and other products from OrbImage in CEOS format are not supported.

OrbImage SeaWIFS data is distributed in a modified CEOS format, and normally consists of 8 or 9 16bit unsigned image bands. A dataset normally consists of five files with particular names.

rw-r--r-- 1 nadeau daemon 3612334 Sep 4 15:27 ANNOTATION
rw-r--r-- 1 nadeau daemon 32673846 Sep 5 10:29 IMAGE
rw-r--r-- 1 nadeau daemon 1536 Sep 4 15:26 LEADER
rw-r--r-- 1 nadeau daemon 360 Sep 4 15:27 NULL_VDF
rw-r--r-- 1 nadeau daemon 1440 Sep 4 15:27 VDF

In order to read a SeaWIFS CEOS dataset the user should select the file name IMAGE. If the ANNOTATION and LEADER files are not named appropriately then the metadata and GCPs will not be captured.

Per scanline orbital information stored in the ANNOTATION file is used to derive a set of 252 approximate GCPs, represented as a GCP segment. These can be used to do a low precision image correction using an application like GCPWorks. Note that thin-plate splines are generally more appropriate than polynomial modelling for the complex of warping SeaWIFS data into geocoded coordinates due to the large region of the world represented.

A variety of header information about the scene location, and acquisition date, orbit, and acquisition parameters is captured from the LEADER file as metadata on each of the image channels. All SeaWIFS related metadata names start with ``Seawifs_''. The following are values for an example dataset:

 Seawifs_OrbitNumber:    74891
 Seawifs_StartTime: 19960813T173940,000             
 Seawifs_EndTime: 19960813T174325,833             
 Seawifs_SceneCenterTime: 19960813T174132,833             
 Seawifs_SceneCenterLatitude:      33.76007781
 Seawifs_SceneCenterLongitude:     -89.02038286
 Seawifs_UpperLeftLatitude:      42.36399801
 Seawifs_UpperLeftLongitude:    -106.17848195
 Seawifs_UpperRightLatitude:      37.11662320
 Seawifs_UpperRightLongitude:     -68.82545473
 Seawifs_LowerLeftLatitude:      29.06083046
 Seawifs_LowerLeftLongitude:    -106.92808289
 Seawifs_LowerRightLatitude:      24.55428087
 Seawifs_LowerRightLongitude:     -74.88265287
 ACQUISITION_DATE: 1996/08/13 17:39:40

SeaWIFS data is also provided by NASA in the SeaWIFS HDF format for some scientific users. OrbImage ordering information can be found on the OrbImage web site, http://www.orbimage.com/.