A minor (but frustrating) error in a Cretan gazetteer

“They said they were hair-dressers but … kind of hard to believe.”

Play It Again Sam

Woody Allen

I’m currently taking Mycenaean and Minoan sites from Crete and putting them into the Mycenaean Atlas Project database.  Today I was spotting sites in the very valuable gazetteer article:  Goodison and Guarita [2005].  Everything was going fine until I reached this:

“31. KHRONI KALYVI/ GANGALES

…

Location: After turning off the Ayii  Deka-Heraklion road towards Gangales,  140m on (just after the river) pass tiny chapel on left of road. 30m further on, cut across fields to the right (180m). The tomb is a few metres NW of a barn.” (1)

This tomb, possibly Early Minoan, is a circular tomb and mound of about 11 m. in diameter.  It was robbed in antiquity and, I suspect, of no really great importance or significance in itself beyond helping to fill out the picture of the extent of circular tombs in the Mesara during the EM.  Therefore the most important thing about it would be its exact position and that's what I want to establish.  There are a number of ambiguities in the directions to this tomb so I decided to take this down to the ground and provide a full description of what our authors are trying to tell us.

The main north-south road through the center of Crete runs from Heraklion to a junction with a major east-west road and very near to the town of Aghii Deka. (just a few km. further on one comes to Gortyn.)   And what our authors are saying is that if one turns towards Gangales (away from Ayii Deka to the east) then, after 140 m. one comes to a small chapel and then a road to the right which will lead to this tomb.

I tried every possible way to move 140 m. to the E from the N-S road to the main E-W road but nothing worked.  Actually 140 m. hardly gets you out of Ayii Deka.  There is a river in Ayii Deka and everything almost fit but didn’t quite.  Especially vexing was my inability to spot any tiny chapel on the edge of Ayii Deka. 

I spent a couple of hours on this and finally I just tried a guess.  Perhaps 140 was a mistype for 1400 (or something).  I started again tracing a 1400 m. route from the easiest turn-off from the N-S road to the east (another guess).  At the end of the 1400 m. trace I discovered everything together, the river, the chapel, the barn … everything.   And the ‘tiny chapel’ really was very tiny indeed; in Greece such a thing is known as a kandylakia – a roadside shrine/contribution box shaped like a full-size church.  And standing next to it was another even smaller and even more elaborate kandylakia.   The people of Greece sometimes erect these kandylakia at a place where a traffic death has occurred.  They form a kind of small refuge where a person might stop and pray during the day or light a candle or give a donation.

I don’t know what these kandylakia are called in Crete but ours look like this:

 

Chapel on L, kandylakia on R.

What about the route itself?

In this aerial photo the 1400 m. route is shown in light brown.  The river which Goodison & Guarita mention is in blue.  

Since our authors don't precisely say here is a close-up of the actual exit that Goodison et al. are referring to when they reference the start of this 1400 m. route.  Here's an aerial photo of it:

The route marked in red is the main highway from Herakleion to Ayii Deka.   The outskirts of Ayii Deka are shown on the left (W).  The turn that you make is labelled 'To the Tomb'.

If you're driving towards Ayii Deka then that turn is shown in the next photo from Google Street View.

Time for a close-up of the route's end and a tentative location for the tomb being sought.

This photo shows the route that you're driving on in light brown.  The river that you pass is in blue and the arrow A marks the position of the 'tiny chapel' and the kandylakia.  The line in purple is the 180 m. path that you take 'to the right'. 

Here is a close-up of the east end of the route.  The blue line is the river that Goodison et al. call out.  The lat/lon pair is the position of the 'tiny' chapel.  The circle is centered by the kandylakia and is 30 m. in radius.  Not surprisingly that brings us directly to the road 'on the right' which leads south 180 m. to the tomb.  Our authors say: 'Present structure: Barely discernible raised irregular circular mound of stones, overgrown by vegetation.   D: ?c. 11 m.  ...' (2)

In this picture there is some ambiguity because the tomb cannot now be seen.  I supposed that maybe the structure was to the SE and there is a circular feature there.  But it is not large enough.  Its diameter is only about 2.7 m. and we're looking for a feature with a diameter of 11 m. (approx.).  I also want to point out the feature that I've called a 'Burn Circle' at the lower left.  I often see these more or less circular features in the olive orchards of Greece; they are really just circles of ash where the farmers have burnt orchard rubbish.  Wishful thinking often converts these things into tholoi.

Goodison et al. would have done their research before 2005.  I was able to find the 11/16/03 image of this area in Google Earth.  It does appear to show an anomaly about 7.5 m. to the NW of the NW corner of the barn.  No other image that I examined shows anything at all in that position.  I have drawn a circle of 11.0 meters in diameter centered on that spot to suggest where the tomb may have been.  I emphasize that this is supposition based on what our authors have told us.

So, perhaps the best position for our sought-after tomb is  35.056539° N, 24.982953° E.


No one claims that their work is error-free.  Substituting 140 for 1400 is a tiny error in a really fine and useful article.   In the field of computer science this would be labelled as just a bug.  I shudder to think how many of these things there must be in my own work.  It does illustrate, however, one of the real advantages that digital representation has over traditional print venues for scholarly work.  This article is going to be around for a long time and the description for Tomb no. 31 will be misleading people for as long as it exists.   If the information in Goodison et al. [2005]  (and several hundred others that I could name) were in the form of a database then such a flaw could be repaired for free and turned around in seconds.  It's just like software in that respect.  No professional expects software to be completely free of errors.  No moral opprobrium attaches to this.  Software authors recognize better than most other professionals that, when it comes to details, the human mind is basically trash.  As a result a large part of software implementation consists of making provision for keeping flaws under control.

One of those devices is the version numbering system.  As hideous as it may sound to an academic it may be time to start versioning articles and books.  The versioning information goes along with the article/book and would explain what has changed since the last version and why.  Of course this can only happen if these articles/books are online.   A consummation devoutly to be wished.

Of course I also think that articles and books shouldn't be printed at all.  It's outmoded.  Why commit errors to epistemological prison?

Finally, let me express my gratitude to Goodison and Guarita for providing this gazetteer from which I've learned so much.

~~~~~~~~~~~~~~~~~~~~~~

A new database for the Mycenaean Atlas Project (www.helladic.info) was delivered on May 11, 2018.  Approximately 35 new sites were added in the Siteia region of Crete.  The new DB is rev 0059.

Also don't miss my review of Against the Grain by James C. Scott.  It's here: http://mycenaeanatlasproject.blogspot.com/2018/02/some-notes-on-james-c-scott-against.html

If you like these posts then please follow me on Twitter or Google Plus (Robert Consoli).

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If you'd like to have a copy of the Mycenaean Atlas database then e-mail me and tell me about your project.  And remember that useful .kml and/or .csv files can be generated directly from all the windows of the website helladic.info   Try it out!

Notes

(1) Goodison and Guarita [2005],  186.
(2) idem.

Bibliography

Goodison and Guarita [2005]:   Goodison, Lucy and Carlos Guarita, 'A New Catalogue of the Mesara-Type Tombs', Studi Micenei ed Egeo-Anatolici [47], pp. 171-212, 2005.

Correspondent Comments on the Suitability of Pleiades Data for Scholars

A friend of mine replied to my post on the inaccuracy and unsuitability of Pleiades data for scholarly work.  (http://mycenaeanatlasproject.blogspot.com/2018/02/pleiades-data-does-crowd-sourcing-for.html)

I reproduce his letter here:

"Pleiades isn't structured to provide a single, accurate set of coordinates, though I think it hopes to evolve in that direction. Its most useful role currently is as a set of identifiers that allow links to superior gazetteers. For example, the huge error for ancient Messene is the result of displaying a calculated representative point that includes one spurious DARMC location (from the modern village of Messene), in addition to a mildly inaccurate DARMC location plus a very accurate DARE location. (DARE has assimilated a bunch of Google Earth-validated ToposText points for Greece, and from other sources as well, but uses Pleiades IDs as an easy pivot to other resources). Some of the tools Pleiades funding has produced for the purpose of improving its data are not being used very much -- one problem being a technological gap between laborious on-the-ground collectors ... and people who automate things."

Now I look at it piece by piece (original letter in red, my replies in black)

"Pleiades isn't structured to provide a single, accurate set of coordinates,"

So then where do we go from here?

" ..., though I think it hopes to evolve in that direction."

Spoiler alert: they're not going to. This would involve an enormous amount of work - actual scholarship. They're not going to commit to this because they think that this can be done on the cheap - through copying other data sets or through crowd sourcing. That's not the way that any of this works. My experience with them is that they will correct an error if you bring it forcefully to their attention but not otherwise.

"For example, the huge error for ancient Messene is the result of displaying a calculated representative point that includes one spurious DARMC location (from the modern village of Messene), in addition to a mildly inaccurate DARMC location plus a very accurate DARE location. (DARE has assimilated a bunch of Google Earth-validated ToposText points for Greece, and from other sources as well, but uses Pleiades IDs as an easy pivot to other resources). "

You've explained Messene but what about all the other errors? Nor have you questioned my estimate that approx. 1/3 of Pleiades has serious errors. What you're describing sounds like a real incestuous tangle. I don't even want to get into unpacking this beyond saying that topographical accuracy does not come from copying other data sets. It's like the old saw about buying a used car: you're just buying someone else's problems.

" Some of the tools Pleiades funding has produced for the purpose of improving its data are not being used very much -- one problem being a technological gap between laborious on-the-ground collectors (like me) and people who automate things. "

Sounds like you're describing Recogito. Is that what you mean? Are there other tools that they support? I tried out their conversion tool Geocollider. It failed miserably.

Everything about Pleiades/Pelagios/Peripleo is sham.  The Barrington Atlas data was useful for its printed purpose but now they're trying to roll that data over into the digital world where its approximative nature makes it unfit for use. And they've wrapped the whole thing up with bad and outmoded ideas - not from scholarly practice, from anthropology or toponymy or history or classical studies or any other relevant discipline - but from computer science. None of what they're doing (crowd sourcing and linked data) has anything to do with any scholarly practice or purpose but this is what they're selling and they're getting pots of money for it. In the end actual scholars wind up exactly where they started - having to do the topography of the Mediterranean from scratch. I actually know a fellow (from a very prestigious school) who's preparing a study of Mediterranean habitations. I was shown one of his spreadsheets and it was stuffed with errors since he had relied on Pleiades. In fact that's where my blog post came from.

I've asked myself what their game is. I suspect that what they want is to license their data (or perhaps their follow-on project Pelagios/Peripleo) to schools for so much per seat and deny access to non-customers. That's a time-honored approach in Computer Science. First get a lot of contributors to fork over their work for nothing under the name of something noble-sounding like 'Open Data' or the 'Semantic Web'. Second, license the whole to third parties and keep all the money.

Although I'm not sure that they can really carry this out successfully because it's the Underpants Gnomes business model.


Bibliography

DARE: The Digital Atlas of the Roman Empire.  https://dare.ht.lu.se/

DARMC: The Digital Atlas of Roman and Medieval Civilizations. https://darmc.harvard.edu/

Geocollider: https://pleiades.stoa.org/news/blog/introducing-geocollider

Recogito:  https://recogito.pelagios.org/

Underpants Gnomes: https://vimeo.com/79954057

Geographic Positions with Two-Digit Fractions

I’m going to keep this simple:

Let’s pretend that the earth is flat (1); for our purposes it clarifies nothing to introduce spherical trig.  

Here you see part of a grid that marks locations.  The horizontal lines are latitude lines.  They measure distances north and south.  The vertical lines are longitude lines.  They measure distances east and west.  

Now let’s say that the locational precision in our system is two decimal places.  That means that no position on our flat earth can be described with numbers more precise than one one hundredth of a degree.  All lat/lon values must be in one of these forms:

0.nn

N.nn

NN.nn

NNN.nn

Our system forbids anything else.  

So let’s say that the lines in our grid representation are exactly two fractional decimal places apart – a line (lat or lon) every one one hundredth (0.01) of a degree.

I’ve put in some suggested numbers for us to work with.  The first thing that you must notice is that unless a location is sitting on one of the vertices (that’s where the lines actually cross) it is NOT REPRESENTABLE in our system.

Let’s look at an example.  Let us suppose that there is a place called, oh I don’t know, let’s make up some unusual name like ‘Prophitis Elias’.  

Now PE is a disadvantaged site because it happens to be located exactly halfway between all the vertices;  at position 34.345 N and 22.835 E.  Our system only allows us two decimal points of representation and so the position of PE is rendered as 34.35, 22.84. (2)   That shifts the position of PI onto the vertex at that position.  This is a deliberately introduced mistake (called ‘aliasing’) that tries to keep the town of PE in the system.  But it’s still a falsification which arises out of the constraints of our system and so it’s up to users to determine how serious this aliasing is.

How serious is it?  How far is PE from its true position under this kind of aliasing?

I’m going to introduce some simplifying assumptions.   I calculate that the circumference of the earth at  35.34 N is 20,291.484 miles [3] and so one one hundredth of a degree longitude at that latitude is 0.56365 miles or 2976.0851 feet.

One one hundredth of a degree in latitude is 3652.14666 feet.  Since our town of PE is sitting exactly equal distances from the vertices the error would be the hypotenuse (A) of the triangle shown here

The aliasing error for the town of PE would be 1826.0733 feet in latitude (NS) and 1488.043 feet in longitude (EW).  These numbers,  1826.1 and 1488.0, are half of the distances mentioned just above because PE is half-way from all the vertices. The actual error (A) is merely the hypotenuse of the resulting right triangle.  Solving for A by the Pythagorean theorem gives us the maximum aliasing error in this system which is 2355.592 feet or 717.984 m.   So the maximum error in this system is almost  ¾ of a kilometer.  I emphasize that this is true only for this latitude; these errors would grow smaller towards the poles and larger towards the equator.

More important: what is the average error?  How far off will we be in the usual case?

The average error has to be less than the maximum error but how much less?  Is it half?

To answer this question I created a simulation and ran 1,000,000 trials several times.  It turns out that the error is not quite normally distributed (a little skewed to the low end) and the average (the arithmetic median) size of the error converges on ~ 1272 feet (388 m.)

Here's a bar chart of 5,000,000 runs.  Each cell from L to R represents an additional 73 m. in error.

To make a long story short – In a positional system limited to two decimal places in the fraction you can expect an aliasing error of nearly 400 m.

Who would create such a limited cockamamie geographical positioning system and expect it to be used for precise work such as describing the position of, oh I don't know, say something like Bronze Age find sites?

Who indeed?

Notes

     (1)    Did you hear the one about the Flat Earth Society circular that claims ‘Thousands of members around the globe’.  Around the Globe!  Get it?, get it?  O.k. back to work you lot!  
     
     (2)   Under normal rounding rules.


     (3)  For radius and circumference of the earth calculation at 35.34 N: