I am working on a project to identify weeds. I used the grid to separate the area. Each cell is marked weed or no weed. I would like to get the GPS of the center of each cell with a weed in it. Does anyone have any idea how to do this? We ultimately hope to upload the coordinates to a drone and have it spray each marked grid. enter image description here

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    I used the grid to separate the area. How is the grid defined? I would like to get the GPS of the center of each cell I assume you mean coordinate?
    – nmtoken
    Oct 25 '19 at 17:45
  • Defined? Not sure. I just used the grid tool 1 X 1 meter. The spray area of the drone is 5 X 5 m so I will use that in the future. Coordinate yes. I almost got it. I used "extract feature by selection" on the grid with the weed points using NUMPINTS > 0. This selected all grids with weeds present. Then I added centroid to each of the selected grids. Then I used the "Add coordinates to points" tool. The cooridnates are in some weird format. Is there a way to change it to GPS? Thank you.
    – Dan Olson
    Oct 25 '19 at 17:52
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    By defined I meant ~ Do you know the geographic coordinates of the bounding box of the grid, was/is it based on some projection, how big are the cells (OK you answered that).~ You should edit the question to add the details
    – nmtoken
    Oct 25 '19 at 17:57
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    You mean you want to know the latitude and longitude of the points you have now created? If so, what software are you using?
    – GBG
    Oct 25 '19 at 18:03
  • Using QGIS. The point is right in the center of each cell with a weed in it. I would like to get latitude and longitude yeah. Thank you
    – Dan Olson
    Oct 25 '19 at 18:20

You have to use: QgsCoordinateTransform(src_crs,dest_crs, QgsProject.instance()) where src_crs is the QgsCoordinateReferenceSystem of you layer and dest_crs the QgsCoordinateReferenceSystem of WGS84.

  • Im new to QGIS. Can you give me simple step by step instructions? Is that a tool I should be looking for?
    – Dan Olson
    Oct 28 '19 at 13:01

Hope this helps:

prj = QgsProject.instance()
dest_crs= QgsCoordinateReferenceSystem("EPSG:4326")#WGS84
src_crs= prj.crs()
transformation = QgsCoordinateTransform(src_crs, dest_crs, prj)

yourPoint = QgsPoint(QgsPoint(994369,515288))#example coords
print(yourPoint.x(), "/", yourPoint.y())

will return 21.3538857925002 / 48.260682704154206

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