I have been trying to overlay two shapefiles of the Harare Zimbabwe streetmap one with centerlines and the other digitized as polygons. the challenge i am facing is that the two overlay but not on the same position they are both projected to wgs 1984 utm zone 36s. enter image description here

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    Were they in a different projection before? If so, what was it? And how did you reproject them? Is the offset consistent? Please add some screenshots to show this. – Dan_h_b Jun 10 '16 at 9:48
  • had defined projection to arc1950 utm zone 36s and the other one had an unknown projection so had to define the projection also so that they overlay. yes the offset is consistent. – shingie Jun 10 '16 at 10:02
  • did you check the datum transformation ? – radouxju Jun 10 '16 at 10:25
  • no i hadnt checked the transformation – shingie Jun 10 '16 at 10:37
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    you should specify a transformation – radouxju Jun 10 '16 at 11:35

Such a slight systematic shift is usually due to a lack of datum transformation before reprojecting the data. You should test the different transformation and your data will overlap correctly. I can't tell which one is best for you based on the information provided, but you can test it relatively fast.

enter image description here

EDIT: if this doesn't work, you have two solutions: The rigourous is to try to find the real CRS as the wrong CRS could have been assigned. Therefore you need to remove prj file of the suspect shapefile (rename with "_old.prj", do not delete) and test all possible CRS by changing the dataframe coordinate system.The pragmatic solution is to use the spatial adjustment tool (in an edit session, make a copy of your shapefile first) in order to adjust the suspect shapefile with links on the reference one. Start with affine transform, and if you notice more distortion you can use rubber sheeting (but then you need far more links, rubber sheeting is really the "last chance" option). Note that your polygon and lines don't seem to have the same precision, so you should not expect a perfect result.

  • If this does not work, you can use the "spatial Adjustment" tool. It is like georeferencing (only for raster data) for vector data. – André Jun 10 '16 at 15:02
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    See if your version has Arc_1950_To_WGS_1984_10 (or 9). It's more accurate than _1. – mkennedy Jun 10 '16 at 16:47
  • okay Andre on the spatial adjustment tool which should l specifically use the edgematch features, rubbersheet feature, transfer attributes etc. – shingie Jun 13 '16 at 7:36
  • Alright mkennedy let me check – shingie Jun 13 '16 at 7:37

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