Harris matrices are notoriously difficult to handle electronically. Several projects that I have seen have something similar to this graph on their excavation forms:

Relationship area of PARP:PS SU form

Recording the associations of SUs looks clear enough with this example but it is usually a disaster in practice, unless one is extremely particular about reviewing old forms. If an SU sheet is filled out for 13040 (trench 13, su 40) one day, then SU 13050 is opened up two days later and found to be the same strata, it is easy, while filling out the form for 50, to say that it is the same as 40 (filling in the center boxes with 13050=13040) but how often will they go back to the 40 form and enter that 13040=13050? I find that this is missed very often on the forms and that gets transferred to the database. This, in turn, ends up being one of the real difficulties in researching the material. The seemingly complete form masks the inaccurate data behind it.

I have tried to make the database fix this problem. In one database recently, I had the database take the relationship mentioned above and make an equation (13040=13050) and look for an inverse statement. If that inverse statement is not found, then I have the database add the inverse statement (13050=13040) automatically. This also works for later and earlier SUs. If the form for 40 says that it is later than 41, the database breaks it down as (13040 > 13041). It that is so it has to create a record that says (13041 < 13040). But since 40=50, then I also have to make records that say (13050 > 13041) and (13041 < 13050). Needless to say, this is a lot of development and it isn’t quite rock solid. It is difficult to work around typos, edits, and record deletion. I will post an example of that at some point.

At PARP:PS, we also had the trench supervisors supply us with a trench-wide matrix at the end of the season. This would be supplied in a number of ways: from colored pencil on grid paper, to photoshop files. Notes on matrix information were kept in trench supervisor’s paper notebooks and the trench wide matrix was only usually done at the end of the season. If a specialist (mostly ceramic) needed the matrix information during the season, the trench supervisor would cobble together their notes and make a hand-sketched matrix of just the specific SUs under consideration.

In 2009, we tried to standardize on using Omnigraffle for electronic matrices. Omnigraffle is rather expensive (59.95 USD for standard academic version, 119.95 USD for the Professional academic version), and we needed a license for each machine. Plus it is Mac only and the personal computers on our project were 50% Windows.

In 2010 we introduced the iPads to the trenches. And we added Omnigraffle for iPad to the software used. The cost suddenly got better. Although Omnigraffle for iPad is 49.99 USD, according the app store licensing structure we can put it on five iPads at a time. We then only need one desktop license to clean up and edit the matrices at the end of the season.

When the trench supervisor created a new SU, they simply switched to Omnigraffle and made the rectangle for the new SU. They could associate, and edit associations whenever they wanted to. Since the iPads are backed up twice every day, the matrices could be looked at by the director, and the latest versions could be delivered to the specialists at any time.

Making matrices on the iPad was one of the easiest things for the teams to pick up and we trained them in the field using a short tutorial designed to have them draw a matrix from Dr. Harris’ own book on the subject. That tutorial is attached here in both pdf and doc format, if you should choose to edit for your own training needs.

Omnigraffle Tutorial.pdf

Omnigraffle Tutorial.doc

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