georef
Differences
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| georef [2021/03/10 20:51] – allchin09 | georef [2021/03/11 00:29] – [Coordinate Conversion] allchin09 | ||
|---|---|---|---|
| Line 131: | 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 | | ||
| + | |||
| + | The [[http:// | ||
| + | ^Datum | ||
| + | |Clarke |S33°51' | ||
| + | |AGD66 | ||
| + | |AGD84 | ||
| + | |GDA94 | ||
| Note: | Note: | ||
| Line 154: | Line 164: | ||
| An explaination of parameters is as follows: | An explaination of parameters is as follows: | ||
| - | == Parameters == | + | === Parameters |
| - | = +proj = | + | == +proj == |
| * Description: | * Description: | ||
| * Value: tmerc | * Value: tmerc | ||
| Line 164: | Line 174: | ||
| * Note: prior to 1936, a polyconic projection was used | * 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 | ||
| - | ^Parameter | + | == +lon_0 == |
| - | |+proj | + | * Description: Longitude of projection centre or true origin (TO) of projection. Also called central meridian (CM). |
| - | |+lat_0 | + | * Value: 151e (for zone 8 only) |
| - | |+lon_0 | + | * Value description: |
| - | |+k_0 |Scale factor | + | * Each zone has a different CM. ANG has 8 zones covering the width of Australia |
| - | |+a |Semimajor radius of the ellipsoid axis |6378339.78||Value in british feet converted to metres| | + | * Zone 8 covers the East of NSW |
| - | |+rf ||294.26||| | + | * Zones and their CM values can be found in the table below |
| - | |+to_meter | + | * Each zone is 5 degrees wide in longitude, starting at 113d30e and ending at 153d30e |
| - | |+x_0 |False easting | + | |
| - | |+y_0 |False northing | + | ^Zone Number |
| + | |1 |113d30e | ||
| + | |2 |118d30e | ||
| + | |3 | ||
| + | |4 |128d30e | ||
| + | |5 | ||
| + | |6 |138d30e | ||
| + | |7 | ||
| + | |8 |148d30e | ||
| + | |||
| + | == +k_0 == | ||
| + | * Description: | ||
| + | * Value: | ||
| + | * 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: | ||
| + | * Value description: | ||
| + | * Based on Clarke 1858 ellposid with a defined as 20, | ||
| + | * A conversion factor of 0.30479947 | ||
| + | |||
| + | == +rf == | ||
| + | * Description: | ||
| + | * Value: | ||
| + | * Value description: | ||
| + | * Based on Clarke 1858 ellposid where the inverse flattening was defined as 294.26 | ||
| + | |||
| + | == +to_meter | ||
| + | * Description: | ||
| + | * Value: | ||
| + | * 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: | ||
| + | * 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 | ||
| + | |||
| + | == +y_0 == | ||
| + | * Description: | ||
| + | * Value: | ||
| + | * Value description: | ||
| + | * ANG has a false northing of 800,000 yards south of the true origin | ||
| + | * Converting into metres is 800,000 / 0.91439841 = 731,518.73 metres | ||
georef.txt · Last modified: 2021/03/11 00:31 by allchin09