georef
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georef [2021/03/10 17:13] – [Coordinate Conversion] allchin09 | georef [2021/03/11 00:15] – [Coordinate Conversion] allchin09 | ||
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Handy tables of parameters can be found [[https:// | Handy tables of parameters can be found [[https:// | ||
+ | |||
+ | === Coordinate coversion for 1 inch to the mile millitary maps (ANG) === | ||
+ | |||
' | ' | ||
Line 128: | Line 131: | ||
| scale factor | | scale factor | ||
- | Other relevant | + | |
- | | zone 8 | + | Sydney Observatory was used as a datum for triangulation, |
+ | ^Value | ||
+ | |Latitude | ||
+ | |Longitude |151d 12m 17.85s east | 151.204958d east | ||
Note: | Note: | ||
Line 151: | Line 157: | ||
An explaination of parameters is as follows: | An explaination of parameters is as follows: | ||
+ | === Parameters === | ||
+ | |||
+ | == +proj == | ||
+ | * Description: | ||
+ | * Value: tmerc | ||
+ | * Value description: | ||
+ | * [[https:// | ||
+ | * Projection used by ANG from June 1936 | ||
+ | * Note: prior to 1936, a polyconic projection was used | ||
+ | |||
+ | == +lat_0 == | ||
+ | * Description: | ||
+ | * Value: 34s | ||
+ | * Value description: | ||
+ | * The true origin of ANG is 34 degrees south | ||
+ | * This is consistant across all 8 zones in Australia | ||
+ | |||
+ | == +lon_0 == | ||
+ | * Description: | ||
+ | * Value: 151e (for zone 8 only) | ||
+ | * Value description: | ||
+ | * Each zone has a different CM. ANG has 8 zones covering the width of Australia | ||
+ | * Zone 8 covers the East of NSW | ||
+ | * Zones and their CM values can be found in the table below | ||
+ | * Each zone is 5 degrees wide in longitude, starting at 113d30e and ending at 153d30e | ||
+ | |||
+ | ^Zone Number | ||
+ | |1 |113d30e | ||
+ | |2 |118d30e | ||
+ | |3 |123d30e | ||
+ | |4 |128d30e | ||
+ | |5 |133d30e | ||
+ | |6 |138d30e | ||
+ | |7 |143d30e | ||
+ | |8 |148d30e | ||
+ | |||
+ | == +k_0 == | ||
+ | * Description: | ||
+ | * Value: 1 (default value for tmerc in PROJ) | ||
+ | * Value description: | ||
+ | * ANG has a scale factor (SF) of 1 at the central meridian | ||
+ | * This means that on the CM, a measured distance on earth will equal the corresponding grid distances | ||
+ | * East and west of the CM, a measured distance on earth will be less than the corresponding grid distances | ||
+ | |||
+ | == +a == | ||
+ | * Description: | ||
+ | * Value: 6378339.78 | ||
+ | * Value description: | ||
+ | * Based on Clarke 1858 ellposid with a defined as 20,926,348 british feet | ||
+ | * A conversion factor of 0.30479947 metres per british foot = 6, | ||
+ | |||
+ | == +rf == | ||
+ | * Description: | ||
+ | * Value: 294.26 | ||
+ | * Value description: | ||
+ | * Based on Clarke 1858 ellposid where the inverse flattening was defined as 294.26 | ||
+ | |||
+ | == +to_meter == | ||
+ | * Description: | ||
+ | * Value: 0.91439841 | ||
+ | * Value description: | ||
+ | * The ANG coordinates are in yards | ||
+ | * 1 yard = 3 british feet = 0.30479947 * 3 = 0.91439841 yards per metre | ||
+ | |||
+ | == +x_0 == | ||
+ | * Description: | ||
+ | * Value: 365759.36 | ||
+ | * Value description: | ||
+ | * ANG has a false easting of 400,000 yards west of the true origin | ||
+ | * Converting into metres is 400,000 / 0.91439841 = 365,759.36 metres | ||
- | ^Parameter | + | == +y_0 == |
- | |+proj | + | * Description: False northing |
- | |+lat_0 | + | * Value: 731518.73 |
- | |+lon_0 | + | * Value description: |
- | |+k_0 | + | * ANG has a false northing |
- | |+a | + | |
- | |+rf ||294.26||| | + | |
- | |+to_meter | + | |
- | |+x_0 | + | |
- | |+y_0 | + |
georef.txt · Last modified: 2021/03/11 00:31 by allchin09