Friday, March 16, 2012

Geographic coordinates in constituency announcements

So far, in all publication within the Royal Gazette which refer to actual geographic coordinates, these are given in the Military grid reference system (MGRS), omitting the obvious zone identifier at the beginning. Additionally, these are (or at least were) in the Thai Indian reference frame, and not the WGS84 reference frame used by GPS, Google Earth and now also in the maps by the Royal Survey Department like the L7018 1:50.000 maps.

However, in the two latest constituency boundary announcements from the Election Commission, a new system of coordinate references seems to have started. Published on March 3 and approved for publication on February 23, the constituencies for the forthcoming municipal election in Yasothon town (เทศบาลเมืองยโสธร) have been changed [Gazette], modifying the boundaries defined in 2004 [Gazette]. And within this announcement, coordinates given as UTM ๐๔๐๗๖๒๙ ๑๗๔๖๘๓๔. Again omitting the obvious zone 48P, and probably still within the Thai Indian 1975 frame. In fact, MGRS is only a different way of writing down an UTM coordinate, the first two digits of the easting and northing each become a letter. Also notable, the UTM coordinates in this announcement have one digit more in both northing and easting, thus an accuracy of 1 meter instead of 10 meter as used in the MGRS coordinates.

And since it is not that many coordinates, I have done the work again to create a simple map out of them, trying to match the boundaries of the constituencies with the boundaries of the municipality as defined in 1994, when the municipality was created [Gazette].

View Larger Map

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