Taiwan Power Company grid

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台灣電力公司座標 (閱本頁於中文框)

台灣電力公司座標(電力座標)值得學習,其遍及全台而可利用定位,作「窮人的 GPS」…

The Taiwan Power Company grid is significant in that it presents a freely available "poorman's GPS" on every power pole and switch box in Taiwan, and could be readily incorporated into projects like Openstreetmap as a supplemental grid. Here we present how to convert the Taiwan Power Company grid into Taiwan datums thus ultimately connecting it to worldwide coordinate systems.

較廣介紹請參 For a broader introduction please see [1].

一般桿牌 A typical pole with grid plate

電力座標與2度TM座標的關係 Taiwan Power Company grid and TM-2 relationship

總攬 Overview

Figure 1. G8150 HD78

圖一 Figure 1: 視本牌 Looking at the number plate with coordinates G8150 HD78 (呼之 call this GPPQQRSTU[VW]). 

G  is a 80 × 50 km rectangle 如圖二 see figure 2.
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

設備密集都市中也有 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

我們首先看看台電公司電線桿的牌子,該牌子的下兩行就是座標,經過簡單的換算,我們可以將牌子上座標換算成橫麥卡脫投影2度TM座標TWD67,這是台灣地圖常見座標系統之一。以下簡單的分析電力座標所分別代表的意義。

Let's take a deeper look at that TaiPower pole number plate. Again, the last two lines of that plate, G8150 HD78, are the coordinates. We can convert them to TM-2 coordinates, version TWD67, one of the common systems found on Taiwan maps. Let's take a look at the meaning of each of those numbers.

A-Z 區 areas

Figure 2. Taiwan: TM-2 TWD67 grid with TaiPower 80×50km area letters

圖二: 以東西寬八十公里,南北長五十公里為範圍,將台灣劃分區域並以英文字母代表所在位置大區域,如台中縣東勢鎮位置為G大區。

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

他區 Other areas:


800×500m

Figure 3. Location of G8150 inside G sector

圖三:G大區共分為一萬個 配電圖圖號,每張圖東西寬800公尺,南北長500公尺。G大區最西側的X座標為170000公尺東,最南側的Y座標為2650000公尺北,而G大區第8150圖區西側之X座標為170000+81*800=234800公尺,南側之Y座標為2650000+50*500=2675000公尺,這就是電力座標G8150所代表的意義。

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.

100×100m

Figure 4. Breakdown of area 8150 from AA to HE

圖四:另G大區第8150號圖又細分東西ABCDEFGH各100公尺,南北ABCDE各100公尺,電力座標HD所代表範圍的西南角即距G區第8150圖西側700公尺,南側300公尺的位置。(註:A=0,B=100,C=200...)

Figure 4. 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, TaiPower grid HD 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...

10×10m

Figure 5. Position of 78 inside G8150 HD

圖五:座標78所代表範圍的西南角即HD區西側往東7*10公尺,其南側往北8*10公尺。

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.

總合 Summing up

綜合以上敘述,電力座標G8150 HD78的2度TM座標分別為

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  米東
2650000+50*500+(4-1)*100+8*10 = 2675380 meters North 米北

所細分圖區雖然還是10*10公尺大的區域,可是對於出外的遊客而言,已經可以精準的得知自 己目前所在的位置。

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.

1×1m

在都市地區,因電線桿∕箱的密度較高,我們還可找到加印個位數字的,第一 數字:米東,第二:米北;例:G8150 HD7812。其精度則達一米,比單 一GPS衛星定位儀測出的座標值還準確(另外,電桿∕箱密的地方,房子也高,此時GPS更難 發揮功效了)。

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…

澎湖 Penghu

澎湖的 x=250000m 線為東經119度,於台灣島不同。 Penghu uses 119 east longitude as x=250000m.E., unlike Taiwan. 

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

金門 Jinmen

金門使用UTM 6度分帶座標系統(其中央子午線為東經 117度,平移500000公尺),(本文所有縱座標均以赤道為原點)。 Jinmen uses 117 east longitude as their x=500000m.E. definition. (This is a 6 degree wide "UTM" grid area.)

金門有兩個同名為a大區。因金門地小,兩a區不衝突。 Jinmen has two sectors both named "Z", which don't conflict as Jinmen is small. 

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

Let's convert point 來換算點 "a" : 

$ proj -le|grep -w intl #猜 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

至 To WGS84 見[2].

烏坵 Wuqiu

未知 Unknown.

馬祖 Mazu

S 區 area. 1954北京座標系, 高度採1985中國高程基準, 因此方格座標一定是Gauss-Kruger六度分帶。

備考 Notes

Grid numbers might be on front or cement base of switch boxes.

所有我們見過的箱子有座標,但有時不但要看前面,也要看其水泥基礎。桿子有的地方舊牌無座標。

All of the switch boxes we've seen have grid numbers, but sometimes you have to look at the cement foundation, as well as the front. The poles on the other hand vary. Some districts only have older poles whose labels lack coordinates.

參閱 See Also

外部連結 External links

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