Maps are essential for walking in unfamiliar places. In Tsukuba, there is a museum called “The Museum of Map and Surveying” that exhibits the technology used to make maps.
I wanted to see the actual electronic reference point there.
The Science Museum of Map and Survey
Mt. Tsukuba
Now that the Tsukuba Express is here, Tsukuba is getting closer. It takes less than an hour from Akihabara. The fare is quite expensive, though.
When we got off at Kenkyugakuen Station, we were immediately greeted by Mt. Tsukuba.
Geodetic Observation Tower and Tsukuba VLBI Antenna
After walking about 2.5 km north from the station, I saw a tower and a large parabolic antenna.
The tower is called the Geodetic Observation Tower. It is 45 meters high. Below this tower is the first triangular point, Tsukuba Origin. But I didn’t know that when I took this picture. If I had known, I would have gone down there and taken a picture.
The parabola is a Very Long Baseline Interferometry (VLBI) antenna with a diameter of 35 meters and receiving frequency bands of 2 GHz and 8 GHz.
In VLBI, radio waves from distant celestial objects are received by antennas at various locations on Earth, and the difference in distance between the antennas in that direction is calculated from the time of each reception. By performing this calculation for a large number of celestial objects, we can determine the linear distance between the antennas.
Isn’t 2GHz affected by noise from wireless LAN or microwave ovens?
Also, at 8 GHz, the wavelength is about 3.75 cm. It would be a challenging task to phase the signals reflected from each area of 35m in diameter at the receiving point. Sounds fun. I want to try it.
By the way, Article 2 of the Ordinance for Enforcement of the Survey Act stipulates that the azimuth angle of the origin shall be the azimuth angle of the intersection of the crosses of the metal markers of the Tsukuba ultra-long baseline radio interferometer observation points. It’s kind of difficult.
In layman’s terms, the origin of Japan’s longitude and latitude is located near Tokyo Tower, and the straight line drawn from there to the parabolic antenna is 32 degrees, 20 minutes, 46 seconds, and 209 seconds off to the east from true north.
By the way, if you measure it with the map at hand, it is about 58.5 km from the origin of Japan’s longitude and latitude to the parabolic antenna. Assuming that the radius of the earth is 6371 km, since the earth is round, one of us needs to be about 270 meters high to be able to see each other (using the Pythagorean theorem). Even the special observation deck of the Tokyo Tower is 250 meters high, so it is impossible to see through it. How in the world did they measure it?
Mappy, who seems to be from the Middle East or India
This is the entrance to the Science Museum of Map and Survey. Mappy welcomed us with a smile. He’s wearing a turban, so I guess he’s from the Middle East or India. He is riding on a magic map, not a magic carpet. But it has casters under it. Does it need to glide like an airplane to fly?
The inside of the building is very interesting. But I won’t write about it because this blog is about outdoor walks.
Spherical model of the Japanese Islands
There’s plenty to see outside the building too!
A spherical model of the Japanese archipelago at a scale of 1/200,000. On this day, I had it all to myself.
Surveying aircraft “Kunikaze”
There is also the Kunikaze, a surveying aircraft that was active until 1983. It is shiny and still looks like it can fly.
Tsukuba VLBI Antenna and Electronic Reference Point Tsukuba 3
But the most exciting part of this walk was discovering the electronic reference point. There are 1300 of them all over Japan, but I had never seen one before. Hmmm, they look like this.
I heard that electronic reference points can analyze position changes with an accuracy of less than one centimeter using GPS. Brilliant!
But wait a minute. Where is the reference position of an electronic reference point? A traditional triangulation point has a cross engraved on the top, and the center of the cross is the reference point. In normal surveying, you set up a tripod on top of the triangulation point and adjust your surveying instruments to that reference.
The electronic reference point is 5 meters high. Is there a crosshair engraved on the top of the radome? Do you set up a tripod on top of it? Isn’t it necessary to have a tower similar to a geodetic observation tower?
Is it the reference position of the electronic reference point?
I took a picture from below, thinking that the reference was the one sticking out a little to the side. But it doesn’t look like a standard for aligning surveying instruments.
Metal markings half-hidden in the outer casing
In fact, it seems that the standard was right under our feet. In the photo, you can see a round metal marker half hidden in the outer casing, and the relative positions of the GPS antenna and the metal marker were measured precisely, so we can start surveying with the metal marker as a reference. I didn’t know this when I took the walk, so I apologize for the unflattering photo.
By the way, did the metal marker ring a bell for you?
Earlier, in the section on the origin azimuth angle, I wrote “the azimuth angle of the intersection of the crosses of ‘the metal markers’ of the Tsukuba ultra-long baseline radio interferometer observation points”. (There should be a metal marker with a cross engraved on it, probably about 10 cm in diameter, very close to that huge parabolic antenna*).
Walking in Tsukuba
After visiting the Science Museum of Map and Survey, it would have been a shame to just leave, so I decided to continue my walk around the area.
The Tsukuba Botanical Garden of National Museum of the Nature and Science
Passing by the University of Tsukuba, I came to the Tsukuba Botanical Garden of the National Museum of Nature and Science on Gakuen Higashi Street. The clematis garden was open to the public, but it was past 3:00 p.m. and the sun was starting to set, so I passed through.
Matsumi Park Observation Tower.
There was a large park called Matsumi Park, so I came here and found a bizarrely shaped tower called Matsumi Park Observation Tower. I was satisfied just by looking at it from the outside.
Full-scale model of an H-II rocket
Next, I saw a full-scale model of the H-II rocket in the distance. I took a picture and went counterclockwise around the Expo Center to find a better view, but I arrived at Tsukuba Station, so I went home quietly.
Walking data
Course: Tokyo Metro Railways Tsukuba Express Kenkyu Gakuen Station -> The Science Museum of Map and Survey -> Tokyo Metro Railways Tsukuba Express Tsukuba Station
Distance: 11.0km
Time: 5h15m (including time to visit the Science Museum of Map and Survey)
(*) The Tsukuba VLBI Antenna was dismantled and removed by March 2017. However, Article 2 of the Order for Enforcement of the Survey Act remains intact. So, the “Tsukuba Very Long Baseline Radio Interferometer Observation Point Metal Marker” remains. (Added on October 28, 2017)
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