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Diary, March 2021

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Tuesday, March 2, 2021

AE Modular

At 12:24, I received the AE Modular synthesizer that I ordered on December 30 last year and which consists of: AE modular STARTER RACK 2 with four additional modules: 2OSC/d, GRAINS, MULTIFX, and MS20 FILTER. Last Wednesday, I received an email stating that it was ready for transport. A closely followed the transport: When opening the box, I noted that the fout additional modules where already installed. I played a little with it.

Lüntener Fischteiche

Conny and I continued walking along the border. This afternoon, we walked through part of the nature reserve Lüntener Fischteiche. We first returned pole 834 because it Nr.13 of Dutch trigonometric point 340306 at 52°07'06,25403"N 6°49'21,75993"E. We searched for Nr.11 (a stone) and Nr.14 (a TP stone), but could not locate them. Next we continued our search for border poles: We encountered the following On the way back, we took a little detour and walked through the forest of the nature reserve.

Wednesday, March 3, 2021

Sun pillar

While biking home, I saw a sun pillar, which is light pillar of the sun. When the sun was setting below some clouds at the horizon, I took the following picture:

Saturday, March 6, 2021


Conny and I continued our search for border poles. We walked through an area in Germany where all the roads are called Nork. We encountered the following border poles: We did see pole 835B from a distance in the fields. From there we walked on the right side of the spring Zoddebeek, which in Germany is called Zoddebach. We got a little lost and had to cross the spring at a weir

Tuesday, March 9, 2021


Since just less than a week, non-essential shops are allowed to open again in the Netherlands for customers who have made an appointment in advance. About a week ago, I made an appointment to visit the charity shop Het Goed between 16:00 and 16:30. At 16:23, I bought the book 1001 Boeken die je gelezen moet hebben edited by Peter Boxall, written in Dutch and published by Librero Nederland b.v. in January 2017, ISBN:9789089988058, from for € 3.95 at the store. I also made some donation to express my gratitude and to compenstate for their losses during the lock-down. I used to visit this shop about twice a week and I might have spend the donated amount in case they would have been open.

Wednesday, March 10, 2021

RD 340306

This evening, I saw a triangle with the letter R.D. in an atlas at the location where we searched for the Dutch trigonometric point 340306. I tried to find some more information about it on some geocaching sites and on one of the sites, I found a link to an excel sheet with information about all Dutch trigonmetric points. To my surprise, I found that point 340306 has been cancelled. On PDOK viewer it is now shown when the RDinfo, Punten dataset is selected. Information about this can be found on RD-coördinaatpunten als open data (in Dutch) when entering the number below 'Puntnummer ingeven'. It gives the following information about the various points involved:

From the drawing, I understand that the distance between Nr 13 and Nr 14 is 156.9, and that 9.5 perpendicular from 66.0 from Nr 13 to Nr 14 is the location of Nr 11 and Nr 12. The drawing seems to suggest that Nr 14 is at the border, but the location is actually in Germany, which matches the description that talks about 24.8 meter South of the forest path.

Thursday, March 11, 2021


Conny and I walked continued our search for border poles. This time we walked near the Haarmühle, which is a watermill just over the border with Germany. The current mill is from 1619. The previous watermill was from 1331. There is a mentioning of the name Haremole from 1188, which suggests that there was already some watermill in that periode. The current watermill was restored in 1988. Since 2000 is also used to produce electricity, We encountered the following border poles:

Friday, March 12, 2021

Game of Thrones: Season 8

This evening, we watched Games of Thrones (season 8). We watched the previous seasons in the past months. often not more than watching three episodes per evening and about five episodes per weekend. When we, after having seen four episodes, discovered that there were only two left to finish the series, we decided to watch the last two as well. I remembered that many people were disappointed when watching the final episode when it was broadcasted. I also recall that it was shown in movie theathers here in the Netherlands. I can now understand why some people were disappointed. It felt a little as an epilogue after the first third of the episode. But it does feel like in accordance with what George Martin might have had in mind to finish this series.

Saturday, March 13, 2021

Dell Latitude D630

This afternoon, when I prepared our Dell Latitude D630 to be used by Andy, I accidently plugged in the wrong power plug, one that has a slightly larger center plug. After some time, Andy pointed out to me that the battery light was blinking. When I plugged in the correct power plug, it kept on doing so. I concluded that I must have destroyed the charging port. I tried to open it, which took some effort, but I was not able to get to the charging port. Because Andy is the only one who has been using it in the past years, I decided to leave it as this and maybe dispose of it. I did take out the 2Gbyte memory module and the harddisk.

Sunday, March 14, 2021

Passing by

Conny and I drove along ten of the cities billboards that usually show information about events in the coming months, but till the end of the month act as an outside exhibition, called Passing By with 19 reproduction of art works of just as many graduates from the AKI from 2020. These are the graduates as we encountered them on our route: Back at home, I made a map of the route we took.

It was a windy day with rain and sunshine quickly following each othere, a typical rainbow day. We saw two rainbows at different locations.

Thursday, March 18, 2021


Conny and I spend some time walking near Losser, searching for border poles. We ended up walking a part along a walking path called Graafschapspad which was flooded at certain locations probably because of the high water level in the Dinkel river. We encountered the following border poles: There are some poles between pole 4 and 5-I, but they are between a nature reserve (on the Dutch side) and private property (on the German side). There are also some poles between 6-I and pole 11 that are along farm fields. When walking back, we looked if we could locate these from the path we walked. I took some tele pictures from places where we thought to see a pole. At home, I did discover a pole in one of the pictures. I think it is either from pole 7 or 7-I. At home, I spend a long time investigating all kinds of maps (from the Dutch websites: topotijdreis, PDOK viewer, and HISGIS, horigheid) because there has been some border changes after the second war. An area of about one square kilometer was annexed in 1949 and for the most of it returned in 1963 except from some farm field on the east bank of the river. I studied some old maps and also discovered something about four poles, numbered 8, 9, 10, and 11, that were placed two by two on both sides of the river as shown on a map from 1832. In the past centuries the river often changed it course and now is east of the location where these poles where placed. I created a KML file (to be viewed in Google Earth) with my findings so far, which I probably will update again. It seems that one pole has survived. In the area an artwork with the name De landmeter (the surveyor ) has been placed. We have not visited this.

Saturday, March 20, 2021

Parsing workshop

This afternoon, at 14:00 (CET), I gave the workshop A modern approach to parsing programs as part of the CyberSaturdays of TkkrLab. For some unknown reason, the mircophone of my headset was not working, and I had to use a MacBook of someone else. My intention of the workshop was that everyone, no matter their level, would get something out of the workshop. But afterwards, I felt that I had failed this objective. I realized that in the past weeks, I spend a lot of time working on the materials and the programs, instead of thinking about the workshop itself. I think that my previous experience would be enough to just improvise during the workshop, but I am afraid I was blinded by my pride to realize that giving a workshop online is a quite different. I think, I should have taken some time at the start to see the attendees and ask them about their experience level. I also think, I should have started with an example of parsing an expression and evaluating its value and use this as a starting point to explain everything that is needed to parse it. Something, like I start doing at 22:22 of the presentation. Taking the normal priority rules used in numerical expression, I could have explained the use of priorities and how you could use a formal grammar to describe it.

And then only explain something about the history of parsing and how I started developing IParse and that I took a very different approach from the traditional way of developing parsers. I remembered, for example, that IParse cannot parse all Context-Free Grammars (CFG), but that this has never been a problem for all the practical grammars that I have encountered in the past 20 years. Apparently, grammars used for programming languages are more limited than the general class of CFG, probably due to what can be easily comprehended by us humans.

Sunday, March 21, 2021


This morning, I was looking through the book Grensgang: een historische reis langs de randen van Overijssel (in Dutch) written by Jan ten Hove (starting from the back). It is about the history of the borders of Overijssel described as a trip along the border. On page 149, I found a reproduction of a drawing by Otto Koolmann about the 'Verzekeringsstenen', which could be translated (from Dutch) to English as 'assurance stones'. They are at a place where a turn of the border with Germany was established in the middle of the river Dinkel. To define it, on each side of the river two poles were placed, where the crossing point of those poles defined the exact position of the turn in the border. However, the river, as most rivers, was meandering, and over time some of the stone poles, (mostly on the German side) were washed away. To overcome this problem, four new stones were placed at a larger distance of the river as kind of assurance. Hence the name of these poles. We realized that the two unmarked stones we found last Thursday might have been two of the four verzekeringsstenen. We also read some account of some unmarked stones on the other side of the river. This afternoon, Conny and I decided to have a closer look and try to determine the location of the stones with GPS. We encountered the following stones and border poles: At home, I used the coordinates to locate the position of the orginal four border poles (with the numbers 8, 9, 10, and 11 of the pre-1949 border) using the drawing by Otto Koolmann. I tried to match these with the cadaster map of 1832 from the area, but failed to make an exact match. The article (in Dutch) De Verzekeringsstenen by Aafke de Wijk suggests that the two stones on the former Dutch side of the river might be two of the original border stones. I think that is not very likely. Conny send me a link to the article Loakgang langs de Markestenen en Rijksgrenzen van de Marke Losser, which was published in Oet Dorp en Marke with some more information about the part of the border we visited. In it we also read that the location were we parked our car last Thursday has a history that goes back to the fourteenth century and that just North of border pole there used to be a neutral area where border disputes were resolved.

Tuesday, March 23, 2021

Border changes around Losser

I continued working on a KML file (to be viewed in Google Earth) about the border changes just North of Losser. I spend a long time determining the position of the border poles 8 to 11 using the available data. The positions I have chosen, are inferred from cadaster data from now and 1832, do not perfectly match with the positions I calculated from the positions of the assurance stones and the map by Otto Koolmann. They are about seven meter off. My GPS measurements of the locations are probably not very accurate. The possibility that the border poles have been moved between the two dates, should not be excluded, because it is known that the poles were washed away several times by the meandering river. I do not know if it is possible to get more accurate GPS locations (without having to spend hunderds of Euro's). I found the ArcGis viewer where you can get GPS coordinates on a recent topographic map. It did show a dot at the location of one of the assurance stones. The GPS locations where close to the one that I measured myself. I used the viewer to adjust the GPS coordinates of some of the border stones along the current border. The KML file contains the following folders: Besides the folders there are also some border poles that were used during periods before and after the annexation.

Sunday, March 28, 2021

Revisiting Coevorden

Conny and I revisited Coevorden to look for border poles we had missed on previous visits after I created a GPX file with waypoints using the ArcGis viewer and downloaded this (through Google Drive) to OsmAnd on my Galaxy Tab 3 tablet. The weather was a bit rainy for most of the time. We had brought some devices to remove weeds and brambles. We encountered the following border poles: We searched for about a quarter of an hour for pole 133-III, cutting away weeds and brambles, but failed to locate it. To our horror, the area where poles 145 to 146 stood is now a construction site with a large warehouse like building surrounded by parking lots (still under construction). It seems the poles have been removed. We also searched for poles 151-VI (D) and 152-I (N). It looks like these two have disappeared.

Monday, March 29, 2021

Idoneal numbers

On February 5, 2019, I wrote about hexagon numbers. Today, I discovered that the numbers I found, are sequence A229757 in the On-Line Encyclopedia of Integer Sequences. With the sequence, there are references to two publications: Reguläre Dreieckpflasterungkonvexer Polygone.and Tiling Convex Polygons with Congruent Equilateral Triangles by Eike Hertel and Christian Richter. The second paper is an extension of the first one with respect to proofs. The numbers for pentagons the numbers are related to the Idoneal numbers. It is not known if there are more idoneal numbers than the one that are known, but there are no more if generalized Riemann hypothesis is true. As a pentagon can often be changed into a hexagon by removing, one would expect that both sequence match with an offset of one. That is indeed the case for many numbers, but not all.

First two flowers

The first two flowers of our magnolia have opened today.

Wednesday, March 31, 2021

24.4° Celsius

The temperature at Twenthe Airport went up to 24.4° Celsius, which breaks the previous record of 23.7° for the temperature on this date in 2017. The predicted temperature according to the prediction at the start of the day, was 21.8° Celsius.

This months interesting links

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