Wednesday, June 2, 2010

BAG file naming convention

Originally posted here: NOAA needs a public software interface specification for multibeam data. Reposted here for discussion.

Next week, I will be talking in Norfolk about technology transfer between NASA And NOAA. One thing that is clear, we need a file naming convention for published data files that come out of NOAA. These things are not fun, but they make or break the long term usability of data. When I join a NASA mission, the first few times I try to use these filename, it is a bit confusing, but once you lookup the codes and start to use them, you realize the power of well controlled file names. The naming convention for NOAA BAGs is great that it has a survey name, but the rest of the filename is basically information. It's done differently and there is no reference in the metadata to the standard applied. To kick off this idea, let us first think about just BAGs. What should be in the filename and how can we code it?

Take a look through the Mars Exploration Rover (MER) Software Interface Specification (SIS): MER_camsis_v4_9-25-07.pdf [JPL]

First, take a look at the Data Processing Level. With multibeam and lidar data, we have the similar kinds of concepts, but the data usually starts off collected with an IMU providing GPS derived positioning (not something we have on Mars at the moment).

Now for the part that I really want you to take a look at: Section 4.4, File Naming, P22. The file names are broken into a whole bunch of fields:

Each of these fields is defined in the document. For BAG instrument type, I could see codes something like this: S = Single beam sonar M = Multibeam, l = topo lidar, L = bathy Lidar, G = predicted from Gravity, c = combined sensors, C = lead line or similar from a Cable, etc. Then when I had a BAG that
was from a bathy lidar, I would not be surprise when I opened it and it did not look like multibeam sonar data. There was no need to look at the metadata (which would not have told me) or the non-machine-readable Descriptive Reports.

The document has some examples of decoding image file names:

These kinds of conventions are really powerful, but they do take a while to create and debug. I've spent hundreds of hours working on spacecraft imaging teams making sure that everything in the SIS document is correct.


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