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Diary, April 2021

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Thursday, April 1, 2021

De Poppe

Conny and I continued our search for border poles. We walked in an area called De Poppe. We encountered the following border stones:

Monday, April 5, 2021


During the Easter weekend, Conny and I went to Voorthuizen where we rented hotel room at holiday part De Boshoek. We arrived on Friday after we had searched for 'border stones' of the city Apeldoorn. In 1750 the border of the municipality of Apeldoorn was established with wooden poles. Around 1794 the 26 wooden poles were replaced with stone poles. Most of these stone poles have since been removed. Along the entry roads, stone name signs of the city have been placed. It is these name signs, on the East side of the city, we have searched. Conny used the report (in Dutch) Speurtoch naar grenspalen and Google streetview to record the location of these in Google maps. Later, I discovered that some of these poles and also some others are indicated on various topographic maps.

On Saturday, we visited the Green Cathedral, which I visited before on August 25, 2016. We also walken around castle Geerestein just North of Woudenberg.

Yesterday, we continued our search for the name signs. This time on the West of the city. We also entered the crown domain Het Loo where we found another name sign just besides one of the original border stones with the letter A and E on opposing sides. We continued walking through the woods, which we felt were rather boring. Today, we decided to go home early and not visit any places on the way home, because rain, wet snow, hail, thunder and strong winds were predicted. We did see some wet snow on the way home.

Wednesday, April 7, 2021


There was about 1cm of snow on my car this morning. The roofs of houses, plants and some place on the ground were also covered with snow. In the past days, there were a lot of winter showers with snow and hail alternating with sunshine, several times even at the same time. On Monday evening and Tuesday morning, there was also some snow on roofs and some other areas. Todaym we also had some rain showers, but later in the afternoon, again some hail.

Wednesday, April 8, 2021


After I came home from work, I worked on a program (at first based on hexagonnum.cpp) to calculate the number of convex polygons that can be constructed from a given number of equal sized, equilateral triangles. When it did produce a sequence that looked correct, I entered it in On-Line Encyclopedia of Integer Sequences. To my surprise, it did not return any results. Instead of suggesting it as a new sequence, I took the advice to first search the encyclopedia. I came along sequence A096004: Number of convex triangular polyominoes containing n cells, which looked like describing what I had calculated. When I compared it with my own sequence, I discovered that the value for fifteen triangles/cells was different. After some debugging, I discovered a bug in my program and after fixing it, it returned the same sequence.

Sunday, April 11, 2021

Het Haagse Bos

Because last week, the German governments demands all negative test for COVID-19 for people crossing the border from the Netherlands, Conny and I decided to halt our search for border poles and instead search for some marke stones and go for a walk through the forests known as Het Haagse Bos where a marke stone can be found. We found the following marke stones: The last stone is there were the marke Lonnekermarke, Lossermarke and Luttermarke meet.

Thursday, April 15, 2021


I have been thinking about genealogy the last days. Yesterday evening, I spend some time adding some data to WikiTree based on some data from the Dutch resource site: WieWasWie. First of all, I realized that the WikiTree is American centered because, for example, the concept of a middle name is not universal. Here in the Netherlands, we do not have the concept of a middle name. Someone can have one or more firstnames, where having four firstnames is not rare. (Not to talk about a generation name in some Asian countries.) The second thing I realized is that although it is possible to add sources, it is not a source based approach. During the night, I thought about an algorithmic approach to genealogy, where the 'family tree' is constructed based on a collection of records. This morning, I spend some time transcribing the marriage certificate of Leonardus van Bragt and Margaretha Dorothea Faase. The result of this is:

Where I have marked all the handwritten parts in italics. The ordinal indicator in the certificate has two dashes instead of one in the above transcription. I have used the Double Low-9 Quotation Mark as the two commas that indicate a continuation with the next line. Something that nowadays is usually done with a dash. This already shows some of the problems with transcribing documents. And, so far, no one has verified the transcription. In a distributed information system, you would at least have some mechanism to sign a transcription to indicate who did the transcription and who reviewed it with digital signatures. And there is also the problem that there could be multiple interpretations of the document and that one would like to record variants.

Next, I spend some time thinking about a way to represent all the data from the above marriage certificate in some form of JSON. Most of the information is already included in the page, but, for example, the information about the witnesses is not included. The extra information could be used to calculate the probability that two people mentioned in different records are indeed one and the same person. The information is also not in a computer readable form, although, I expect that it is retrieved from some kind of database with a welldefined structure. It would be nice if there is some kind of REST API to query this database. Below an example of how the information in the marriage certificate could be represented in a way that could be processed by a means of an application that constructs a family tree.

{ "source":{
    "Document type":"BS Huwelijk",
    "Institution name":"Noord-Hollands Archief",
    "Institution place":"Haarlem",
    "Collection region":"Noord-Holland",
    "Registration date":"07-05-1890", 
    "Certificate place":"Schoten"},
           "name":"Leonardus van Bragt",
              "name":"Willem van Bragt",
              "name":"Maria Elisabeth Alders",
        "bride": {
           "name":"Margaretha Dorothea Faase",
               "name":"Jacob Faase",
               "name":"Petronella Catharina van der Veld",
            "name":"Franciscus Faase",
            "relationship":{"type":"uncle", "of":"bride"}},
            "name":"Johannes Franciscus Faase",
            "relationship":{"type":"uncle", "of":"bride"}},
            "name":"Cornelis Hendrik van Looij",
            "relation":{"type":"uncle through marriage", "of":"groom"}},
            "name":"Johannes Alders",
            "relation":{"type":"uncle", "of":"groom"}}]}}
      {"person":"Franciscus Johannes Faase", "signature":"bd078fe...."}]}

As is often the case with a more formal approach to solving a problem is that it requires a lot of more effort (and a different kind of mindset) than a more informal approach. Also it requires a greater attention to details of the people involved. And we should not forget that reality is always more complex than one thinks at first and that it is thus very difficult to develop a formalism which covers all cases.

Saturday, April 17, 2021


Conny and I went walking through the adjecent forests Snippert and Het Haagse Bos. At one point we came to a location where the path was submerged in water and we wondered whether there was a way to get to the other side when there appeared a woman on the other side, who wanted to get to our side. After some searching, we found signs of a small path leading around the area, which seemed to have been used for some time, because at one place there were three wooden trunks laid side by side over a water filled ditch. During our trip we found two two marke stones:

Sunday, April 18, 2021

In full bloom

Today, finally, all the flowers of our magnolia opened. It is almost three weeks ago that the first flowers opened. The temperature has been quite low for the time of the year in recent weeks, even dropping below zero degrees Celsius, causing some of the flowers to turn brown. But this afternoon all the flowers had opened and you could smell the nice scent of the magnolia in the garden.

Monday, April 19, 2021

Hexagon puzzel

I gave Conny a small wooden puzzle as a present. In the Netherlands it is sold under the name Hexagon puzzel. It is produced in China, Yunhe County, Lishui City. The product model is XC-808 with the name Interesting Changeful Puzzle. She wanted to know how many solutions it had. After some wrong tries (including not realizing that the pieces could not be used upside down), I arrived at the conclusion that there are 4702 solutions excluding solutions that are the same with respect to rotation of the whole solution. I took the btc24_to_ec.cpp program, which I developed for the Beat the Computer No. 24 puzzle, and made it into a more generic program for puzzles on a hexagon grid (with either hexagons or triangles), calling it hexagon_to_ec.cpp. The command line arguments 1 --flat need to be used for the Hexagon puzzel. The output is fed into an exact cover solver and postprocessed with a small program that makes a letter string of each solution. Below all the solutions are shown in a random manner or can be traversed using the buttons. (The 'a' piece is always placed in the same orientation.)

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Tuesday, April 20, 2021

Groot Peter

Conny and I walked to the shopping center called Winkelcentrum Zuid to visit some shop and way home we went to see the marke stone Steen bij Groot Peter (33.34-05). This a replica that is placed on September 16, 2016 in the North East corner of the intersection of Wesselerbrinklaan (runing North-South), Het Bijvank (on the West). and Het lang (on the East). The original marke stone was in the middle of Wesselerbrinklaan just South of the intersection . Behind the stone (as seen from the center of intersection) there are a number of oak trees that belonged to a farm called Groot Peter. The kadaster of 1832 shows a farm called Peters at that location. Often when a son of farmer would start a new farm near the farm of his father, the names of the farms were prefixed with the words Groot (big) for the original farm and Klein (small) for the new farm. This is probably how the name Groot Peter came into existence. The adjective Klein and Groot are also found in surnames from people coming from this region, because for a long time people were named after the farm where they came from instead of with a surname or patronym.

Thursday, April 22, 2021

GOGBOT café, яєαℓιту ιѕ ѕуηтнєтι¢

I watched this GOGBOT café on YouTube. It has talks by: Followed by video screening of Kesson live coding + AI generated visuals based on a sound recording of Chebedajha (aka Jeannetta Petrik).

Saturday, April 24, 2021

Witte Veen

This morning Conny and I went walking in Het Witte Veen (The White Peat), a peat and forest area near the German border. At, 9:01, we visited the triangulation point 340204, which is on a stone. At 10:18, we visited triangulation point 340329, which is a bolt on a small building. At 10:35, we visited triangulation point 359306. Not sure if we actually saw it, because some note seems to suggest it is located underground.

Wednesday, April 28, 2021

End of curfew

Today, the curfew ends together with some other restrictions, one of them being that you no longer have to make reservation to visit a non-essential shop. On my way home, I visited charity shop Het Goed. There were some long queues before some large retail shops this afternoon. It is a little strange that some restrictions are lifted, because there is no real sign that the number of infected people is dropping. The number of people at the ICU of hospitals in the Netherlands remains high. We are still at the top op the fourth wave were the numbers are higher than during the second and third wave. Yesterday was Koningsdag (King's Day) and many people went to the city centers to celebrate it. It seems that people no longer view COVID-19 as a serious problem and are acting like it.

This months interesting links

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