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I have a coordinates that I would like to plot on Google Earth. The coordinates I have appear to be in SAD69, a Brazilian projection. I need to convert them to latitude and longitude.

I tried importing into QGIS as a CSV file in SAD69 and then exporting as a CSV in WGS84. However, the coordinates I have do appear to be in the correct place. My point should be in central Brazil, however when open a SHP file of Brazil and add the point does not appear anywhere near Brazil at all.

The coordinates I have say:

SAD 69, MC 45° W coordenadas Plano Retangulares Relativas, Sistema UTM: E=721320.945 e N =82009367.716

As I understand it, when importing the coordinates into QGIS, E=721320.945 is my X coordinate and N =82009367.716 would be my Y coordinate.

Do I need any other data?

I don't understand what MC 45° W means in this context.

Based on the coordinates I have, using the SAD69 projection, the points don't seem to be in Brazil at all.

See screenshot:

QGIS Import Point

enter image description here

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  • "the coordinates I have do appear to be in the correct place" - you rather mean: do NOT apear in the correct place, right? As @Pointdump already mentioned, you probably used the wrong CRS. In QGIS, you have different CRS available with SAAD69, both geographic and projected. Find out the correct one. If you need help, you should provide at least some examples of your data - coordinate values you have and correct location where they should appear: correspoinding correct lat/lon values. Commented Oct 2, 2021 at 9:33
  • Also make sure you correctly understand the use of projections/CRS - see e.g. here: gis.stackexchange.com/a/392388/88814 and gis.stackexchange.com/a/383437/88814 Commented Oct 2, 2021 at 9:36

2 Answers 2

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The data source manager does have the wrong coordinate reference system, as Pointdump said. The fact that the column headers are "East" and "North" imply that the values are in a projected coordinate reference system (ProjCRS) rather than latitude-longitude in a geographic CRS (GeogCRS). This line:

SAD 69, MC 45° W coordenadas Plano Retangulares Relativas, Sistema UTM: E=721320.945 e N =82009367.716

does state explicitly that the coordinates are in UTM, or relative rectangular plane (Plano Retangulares Relativas). I believe MC should be translated to English as central meridian ('meridiano central' in Portuguese) which identifies either UTM zone 23 North or South. I think there's an error in the Northing value in the line above. Either it's 2009367.716 which would put the point in the 23 North zone, or its 8009367.716 which would be in 23 South zone. At the equator, North zones, Y/Northing values start at zero, while South zones are 10000000 at the equator and get smaller as you go south.

EPSG well-known ID for SAD69 UTM zone 23 South is 29193. EPSG has no entry for SAD69 UTM 23N, so another argument that the data is in 23 South.

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EPSG 4618 is a Geographic Coordinate System. Its Units are Degrees. Your Coordinates are most likely UTM.

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