Taiwan Power Company Grid and TM-2 Grid Relationship

• ENGLISH ONLY auto-stripped version of
• Chinese+English version.

1999 photo: author "caught red-handed" copying coordinate (B)6737 AE90. Coordinates were once a big secret in Taiwan. Heping E. Rd., Taibei.

Your coordinates are right there on the nearest electric pole -- How to use Taipower's pole and box numbers to get your TM-2 degree coordinates

Understanding coordinates on utility pole numbers, a Taiwanese example

Whereas the reader is surely a map reading and GPS smarty or expert; and Whereas the reader probably has ignored all the little funny numbers on the utility poles and boxes that have surrounded you for the first half of your life; and Whereas I have reached great fame and glory by decoding these numbers here on Taiwan, a sort of poor person's GPS; (plus, next time non-geographically oriented friends invite you to their ranch, just ask them to read you a pole, you'll be there in no time.) Therefore, it's time for the reader to investigate the issue! I mean how are you going to understand the rhythms of the universe when you don't even understand what your front yard's utility pole is trying to tell you, Holmes. (Plus, one day when your or the Government's GPS batteries run out, where's your backup system? I've got mine. (At least where there are roadside utility poles to read.))

To get started, take a look around yourself, e.g., here on Taiwan the telephone poles don't say much, but the electric company's poles and switching boxes have lots of juicy numbers to decode. First plot a few on paper with their relative positions and see if you can decode them on your own. When I first tried, I got the Y coordinate right but X was always off... I gave up and marched into the local electric company service center and took a look at their maps... ah-ha, a rectangular grid! You see, their map paper is rectangular and the first part of the pole number is a map number...(How brilliant, there should be a law, every county and state's borders should be adjusted to 8:5 rectangular proportions to fit standard paper sizes, and the ideal eye-comfortable map proportions.)

Dec. 2001: I swear within two seconds I can already put my finger on where I am on the map, whilst your mom still hasn't got her GPS out of the holster of her cowboy pants. Disclaimers:

1. My power company's poles have got coordinate information on each roadside pole number plate. Check your utility poles...
2. My pals made it into an atlas. [However adding the utility co.'s system to a regular map is easy.] Grid conversion computation has thus been already done before we leave home.
3. I only read the first line of the pole coordinates, for a thumb size 800 x 500 m. fix on their 1:50000 atlas.
4. Look mom, no batteries.

I use the numbers of the Taiwan Power Company's poles and boxes to get my coordinate position, a sort of "poor man's GPS". You too can be a utility pole whiz -- check your poles!

Taiwan Power Company's grid numbers, seen on many electric poles and switching boxes throughout Taiwan, are one way of describing your geographical position. Latitude and longitude is another way, but the major way used on government maps here is the TM-2 system (TWD67). Let's see how it relates to the TaiPower's system. Perhaps it is possible to navigate around Taiwan just using these pole and box numbers, without having to learn Chinese, or wait for the government to hurry up and please accept Hanyu Pinyin romanization of street signs. By the way, the below calculations are unnecessary if one makes or buys maps with the utility company's grid numbers already added. TM-2 stands for Transverse Mercator projection, focused for coverage over 2 degrees of longitude, e.g. 120 to 122 east.

, real example

Figure 1. Looking at the number plate with coordinates G8150 HD78 [call this GPPQQRSTU[VW], G is a 80 x 50 km rectangle, (Taiwan is divided into several of these rectangles.

PP increments by 1, every 800 m eastward,  00-99
QQ increments by 1, every 500 m northward, 00-99
R  increments by 1, every 100 m eastward,  A=0...H=7
S  increments by 1, every 100 m northward, A=0...E=4
T  increments by 1, every 10  m eastward,  0-9
U  increments by 1, every 10  m northward. 0-9

In equipment-dense cities often there are additionally:

V increments by 1, every 1 m eastward,  0-9
W increments by 1, every 1 m northward, 0-9

(Hmmm, one-meter precision, bet your mom's GPS can't do that.)

Let's take a deeper look at that TaiPower pole number plate, mine infact. Again, the last two lines of that plate, G8150 HD78, are the coordinates. We can convert them to TM-2 coordinates, version TWD67, for use with government maps, GPS, etc. Let's take a look at the meaning of each of those numbers.

Figure 2. As we see, TaiPower has divided Taiwan into 80 km wide, 50 km tall lettered rectangular sectors. For instance, the author lives in Taizhong County, Dongshi Township, which lies in the G sector.

Other areas: I: underwater; S: Mazu; U: only about 30 hectares; X, Y: Penghu; Z: Jinmen.

Figure 3. This G sector is divided up into 10000 charts back at the electric company office. Each covers 800 * 500 meters. The west edge of sector G is at x=170000 meters East. The south edge is at y=2650000 meters North. The west edge of the 8150th chart is at x=170000mE + 81 * 800m = 234800mE, the south edge is at y=2650000mN + 50 * 500m=2675000mN. Now we understand the meaning of G8150.

Figure 4. OK. This 8150th sector is further given ABCDEFGH grids, going west to east, each 100 meters apart; ABCDE grids south to north, each 100 meters apart.

As can be seen, power co. grid HD's area's southwest corner lies 700 meters east of the west edge of box 8150, and lies 300 meters north of the south edge of box 8150. Note, A=0, B=100, C=200...

Figure 5. Next, the "78" portion of the grid has its southwest corner at 7*10=70 meters east of the west edge of area HD, and 8*10=80 meters north of the south edge of HD.

Summing up the above, power co. pole/box grid number G8150 HD78's TM-2 grid value is:

 170000+81*800+(8-1)*100+7*10 =  235570 meters East
2650000+50*500+(4-1)*100+8*10 = 2675380 meters North

The smallest unit of our grid is still a 10*10 meter square, but that ought to be small enough for, say, a traveler to find his spot on maps. In cities, where electrical line density is high, we can often find box and pole labels with an additional two digits, e.g. G8150 HD7812, which means add 1 meter east and 2 meters north to the above result. Indeed, the dense part of cities have tall buildings, hindering Global Positioning System (GPS) reception, so with one meter accuracy, it seems we do better than the basic hand held GPS in this case [?!smile].

Photo: To increase the challenge, there are also old style pole band labels with numbers often fallen out, here tugged with my pinky finger.

In conclusion, next time you go to a friends mountain top hideaway, just ask them their electric pole or box number --- no need for confusing road addresses. Of course you had better ask them for a couple more nearby label numbers too, in case there is a pole that has been transplanted along with its old label. If you forget to bring a compass, or can't find the north star, the relative positions of two poles/boxes can be used to compute north, south, east, west too!

[In case you haven't seen me mention it elsewhere, be forewarned that there are still large areas of Taiwan with old poles that don't carry coordinate information. The boxes all do but they are mainly only in the cities.]

Sometimes you must check the cement base to find coordinates

All of the switch boxes I've seen have grid numbers, but sometimes you have to look at the cement foundation. The poles on the other hand vary. Some districts only have older poles whose labels lack coordinates. Or maybe the local administrator isn't using the new scheme yet -- let them know.

Superfluous numbers

Additionally, A1234 BC5678 is mostly abbreviated A1234 BC56, and sometimes even 1234 BC56, or how about in Zhanghua, where one sees e.g. G4028C BC23-PD. An extra C in front and PD at back. Here the PD refers to the type of switching etc. device installed -- ignore it. The C can also be ignored. It refers to a more detailed set of maps at the electric company office -- a block of four centered on EC0500.

In Dongshi, I saw GE9800 G7666. This of course is just G7666 GE98(00). In Guandu folks have spotted a box painted with Chinese "Tu2hao4 (map number) B5758 Zuo4biao1 (coordinates) DA04".

Also note we are talking about electric company equipment, not telephone poles, etc., and not high voltage towers, so don't climb them.

Street lamp numbers

In Taizhong City I ran across some street lamps numbered

00595 25G6349FE94
00597 25G6349FE90
00598 25G6349FD88
00599 25G6349FD77

At left is merely a serial number increasing lamp to lamp along the road. At right is our familiar TaiPower grid number. The 25 awaits further investigation.

Atlases

With TaiPower grids

• Sunriver

Programs

Already there are many TaiPower grid programs.

$ echo G8150 HD7812|./taipowergrid|./xylonlat
##1 G8150 HD7812
#1 235571 2675382
TWD67:
235571 2675382
120.857978243173 24.1836801864713
120d 51m 28.72s 24d 11m 1.25s
TWD97:
236399 2675176
120.866138239638 24.1819144465914
120d 51m 58.10s 24d 10m 54.89s

Please now see Taiwan GPS and TWD67, TWD97, WGS84 coordinate transformations.

Penghu

Penghu uses 119 east longitude as x=250000m.E., unlike Taiwan.

+------+2664000
|  X   |
|      |
+------+2614000
|  Y   |
|      |
+------+2564000
275000 355000

Jinmen

Jinmen uses 117 east longitude as their x=500000m.E. definition. (This is a 6 degree wide "UTM" grid area.)

Jinmen has two sectors both named "Z", which don't conflict as Jinmen is small. Our program can still deal with it.

+------a------+2725800
|  Z   |  Z   |
|      |      |
+------+------+2675800
552700 632700 712700

Let's convert point "a" :

$ proj -le|grep -w intl # Guessing
intl a=6378388.0 rf=297. International 1909 (Hayford)
$ echo 632700 2725800|proj -I +proj=utm +lon_0=117 +ellps=intl
118d18'40.019"E 24d38'25.43"N

To WGS84

2007.9: I'm old and forgot how to convert to WGS84. However let's try:

$ programs/taipowergrid file_full_of_Z_lines|perl -alnwe \
'if(/^\d/){$_=join " ",$F[0]+275,$F[1]+5};print if /./'|
proj  -I -f %.6f +proj=utm +lon_0=117
#1 Z0156 HD3215
118.326956 24.444907
#2 Z0063 DC3879
118.315504 24.476288

Wuqiu

Unknown.

Mazu

S area.

2007/9 Miller Liu reporting: 2007/9:"1954, 1985, Gauss-Kruger" knowledge under construction.

Tool for map edges: each kilometer's TaiPower grid number: existing map grids: output; source: download from index page.

Note that I am not attempting to discuss the merits of some of the design choices made by the power company here. I'm only doing a cursory introduction to it. Note however that 8:5 (of the 800 x 500 m. grid) is often cited as ideal dimensions for ease of use of atlases.... Actually they chose it to match the size of the chart paper available, I believe.

And, with a 1 minute pencil addition to a topo map, it's like God(tm) came down and hung those B-5, A-3... kiddie map index numbers on every pole, for our convenience... if you know what I mean.

This road lacks a name, however its Y coordinate is the same as is an east-west road, and each pole sports this same coordinate, hence it's just like a road name sign, but smaller.

Original article : ["Your coordinates are right there on the nearest electric pole -- How to use Taipower's pole and box numbers to get your TM-2 degree coordinates"] : 4/1998 Taiwan land administration magazine #152 P. 34-36

You see, it all came clear one day as I was sitting in my mountain top retreat. I noticed the birds, then the bees, then the numbers on the electric poles.

Enlarged photos are on my "me" page .

This page should one day be edited into Wikipedia (already a Chinese page) or Wikibooks. See also Wikipedia:Utility_pole#Coordinates_on_pole_labels

Copying welcome. Copyright: GNU General Public License.

Last modified: 2007-11-28 04:06:32 +0800