USGS Home
Contact USGS
Search USGS

Receipt of AVHRR Data Tapes (Inventory)

M. Sarges, G. Kluck, J. Powell, D. Hollaren Define transfer formats, media, frequency, and shipping procedures i.e., packing documents, tape mappers, etc.

The AVHRR data shipped to EDC always consists of 5 channel, 10-bit raw data with 2048 pixels per line. The 10-bit data is stored in 16 bits or the three 10-bit pixels are stored in 32 bits. The sending center specifies if the data is packed or unpacked on the media.

At a minimum, the first 103 words from the raw/acquired data are sent to EDC in order for Operations to ingest the scenes properly.

The participating stations must define how their dropped or missed data lines are corrected or compensated for in order for EDC's ingest procedures to work properly.

The most common scene format received by EDC is Band Interleaved Pixel (BIP), but BIL or BSQ are accommodated also. EDC does receives ANSI labeled, level 1b and Sharp formatted scenes.

EDC assigns a three character CEOS ID to indicate the specific receiving station that captured the data. If a receiving station code has not been established by CEOS, Data Management will create one and forward it to the proper EDC CEOS representative for submission and approval.

An example would read such as: AH11071591130422. Not all stations follow this.

For multi-file, non-ANSI labeled tapes, CSB requests a tape mark to signify the END OF FILE (EOF), and two tape marks to indicate the END OF VOLUME (EOV) in order to process the tape properly. This has been generally followed by the participants.

EDC prefers to receive all AVHRR data on 8mm tape cartridges because of their small physical size, large capacity, and growing international acceptance. Data Management has received data on 3480 tapes, 8mm and 4mm cartridges, and 9 track tapes.

EDC receives shipments from the receiving stations roughly every one to two months. This schedule has, for the most part, worked well in that it affords Computer Operations (Ops) a little more time to process the data than a shorter schedule would provide.

ESA typically sends EDC less than full 8 mm tapes due to the nature of their process flow. EDC, however, will normally send ESA copy data back utilizing most of the 2.3 GB low density 8mm tape to minimize tape handling & shipping costs. So far, 25015 scenes have been shipped to ESA on 1145 8mm tapes.

On packages received by EDC, we have requested that an itemized listing of the number of tapes, an individual tape directory in hardcopy form with the file sizes, file contents or file identifier (scene id preferred), ship date, station ID and a return address be included with each shipment.

Tape and shipment verification procedures include verifying the number of files, readability of the tapes, etc. The data tapes are logged into the digital archive database for tracking and environmental storage.

Data Management has been receiving and logging all 1-KM tapes and forwarding the shipment to CSB support for scheduling/processing. Incoming tapes are entered into the 1KM AVHRR Tape Receipt data base. Incoming tapes go into the tape library code 019 and are held until the contents have been processed and verified. CSB then plans on scratching and reusing the tapes following a scratch confirmation from Data Management. Data Management uses a unique labeling system and assigns tape locations based on the following pattern: KM####. The tape librarians are initially logging in the tape records.

Data Management forwards tape inventory listings on a Data Management form to CSB to use as a reference tool tracking how much data to expect when tape read/parity errors are encountered. Problem tapes are returned to Data Management for replacement through communication with the proper ground station via Information Systems Management. CSB has adopted a readability exception form that is used to document damaged, lost or problem tapes to Data Management. To keep logistics manageable, problem tapes are not returned to the sender.

The team has recommended that all of the ground stations hold the data that was sent to EDC (via ESA or CSIRO in some cases) at least six months to ensure that EDC has successfully read the data. EDC is using the incoming station tapes to send back to participants any in-kind data or as ESA copy tapes. EDC is holding the received media in EDC' digital archive only long enough to ensure that we have successfully converted the data to EDC's format (typically six months).

Data Management and CSB are using the CEOS-WGD Catalog Subgroup approved CEOS common station codes in ingest tables. All 1 km participants are asked to imbed their specific station code in the header file of each tape sent to EDC. The AVHRR Production Data Base and the Global Land Information System receiving station fields were modified in June of '92 to accommodate new CEOS receiving station codes. Data Management provides tape labels for the received data to be ingested efficiently and has procedures in place to ensure that all of the data received were ingested.

Back to 1-KM Homepage