Crashbar Posted July 10, 2022 Posted July 10, 2022 I have noticed that JTAC reads me 8 numbers instead of 6 for the MGRS coordinates. Has this changed recently? Also, I was hoping someone who is more knowledgeable than me wouldn't mind showing me how to properly reduce from a MGRS 10 digit number down to a 6 digit number. For example: DP 21708 60709 to DP ??? ???. Thanks!
rob10 Posted July 10, 2022 Posted July 10, 2022 (edited) 2 options: change your co-ordinate entry to PRECISE in the HSI DATA subpage (OSB 19) and enter all 10 digits for a more precise location (** this is for F-18 ** should be possible in other aircraft but I don't have the details on them at my fingertips) OR: take the first 3 digits of each part (divide it into 5 digit sets if it doesn't give you the space and just gives all 10 digits together), preferably round the 3rd digit of each set based on the 4th and 5th digit. If the JTAC is lasing for you the less precise option probably gets you close enough. Generally worth entering them all if you are given them. If you're flipping back and forth between 6 and 10 digit co-ordinates, you can add 2 zeros on the end of each set (i.e. xxx00 xxx00) to pad it out to a precise entry. Edited July 10, 2022 by rob10
Frederf Posted July 10, 2022 Posted July 10, 2022 8 hours ago, Crashbar said: I have noticed that JTAC reads me 8 numbers instead of 6 for the MGRS coordinates. Has this changed recently? Also, I was hoping someone who is more knowledgeable than me wouldn't mind showing me how to properly reduce from a MGRS 10 digit number down to a 6 digit number. For example: DP 21708 60709 to DP ??? ???. Thanks! I can do you one better than that. By understanding MGRS you will be able to answer your question by yourself. For example the Eiffel Tower in Paris, France is at 31U DQ 48251 11939. The meaning of each part is: 31U DQ 48251 11939, grid zone is the largest area type 31U DQ 48251 11939, grid square is the second largest area type inside a given zone 31U DQ 48251 11939, easting is a measure from the western edge of the grid square to the location 31U DQ 48251 11939, northing is a measure from the southern edge of the grid square to the location The way easting (or northing) distances work is the following: The distance can be indicated by any number of digits 48251, the location is 40,000 meters east of the western edge of the grid square 48251, the location is an additional 8,000 meters east of the western edge of the grid square 48251, the location is an additional 200 meters east of the western edge of the grid square 48251, the location is an additional 50 meters east of the western edge of the grid square 48251, the location is an additional 1 meter east of the western edge of the grid square So the distance is 40,000 + 8,000 + 200 + 50 + 1 meters from the western edge of the grid square to the location. Similarly the distance is 10,000 + 1,000 + 900 + 30 + 9 meters north of the southern edge of the grid square. In order to fit a numerical location (4, 6, 8, 10, 12, etc. digits) into a system which can accept a smaller numerical location you have to lose digits. Officially you only truncate so "39" becomes "3" not "4" because in some situations rounding will push you over the border into a new grid square or even grid zone, breaking everything. Most of the time rounding is fine though. You drop the least significant digits in pairs, one from easting and one from northing, until it fits in the new space. 48251 11939, remove these to fit into 8 digit 4825 1193, remove these to fit into 6 digit 482 119, remove these to fit into 4 digit 48 11, remove these to fit into 2 digit 3 5
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