Mapping and nature of the cartographic projection

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07-08-2022 12:53 PM
kurdishbrwar
Occasional Contributor
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Greetings, the subject is inquiring about the subject of the map and the correctness of the drawing. I drew a map a few days ago and as it was shown in the first figure, and based on the program’s base maps service, and when I compared it to an old map of northern Iraq dating back to 1986, I noticed that there is a creep in the location and location of the drawn phenomena. Amending the maps annually because the earth under us crawls annually by a small number of millimeters to several centimeters, or does this issue have anything to do with and only the old map could have been drawn with another drawing site? Thank you very much if you explain the idea to us more. Thank you.

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HeatherSmith
Esri Contributor

Hi @kurdishbrwar ,
Your new (pink) data aligns well with the basemap, so I think you can assume it is correct, while the old map is inaccurate.
The old map is a raster image, so it may have been georeferenced from a paper map or image. It's possible that it wasn't georeferenced very cleanly, or was georeferenced against inaccurate reference information. If you need it to align it correctly, you could try to georeference it again yourself.

It may also not align properly because of coordinate system mismatches. Check to see if the new data, the old data, and the map itself are all in the same coordinate system. If they are not, a transformation might be required.
You might find this article helpful if you need to work with transformations. It is written for ArcGIS Pro, so the steps will be different, but the theory will remain the same for ArcMap.

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HeatherSmith
Esri Contributor

Hi @kurdishbrwar ,
Your new (pink) data aligns well with the basemap, so I think you can assume it is correct, while the old map is inaccurate.
The old map is a raster image, so it may have been georeferenced from a paper map or image. It's possible that it wasn't georeferenced very cleanly, or was georeferenced against inaccurate reference information. If you need it to align it correctly, you could try to georeference it again yourself.

It may also not align properly because of coordinate system mismatches. Check to see if the new data, the old data, and the map itself are all in the same coordinate system. If they are not, a transformation might be required.
You might find this article helpful if you need to work with transformations. It is written for ArcGIS Pro, so the steps will be different, but the theory will remain the same for ArcMap.

kurdishbrwar
Occasional Contributor
Hello, Greetings, Mrs. Heather Smith, your answer is more than wonderful, scientific and logical. I will do what you indicated in the response and I am happy for your response to the post. Greetings again, your colleague Sabah.
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