Shape file doesn't line up with world imagery

[caitlinpohle]

I have a question maybe someone can help with- I have a world imagery layer from Arcgis online and a shape file, they don't quite line up (they are in different coordinate systems). When I change the shapefile coordinate system to match the world imagery layer, it ends up out in space or doesn't show up at all. The layers do not appear in the georeferencing tool bar. Any ideas? I think it must be a simple fix.......

[JorgeOrellana]

Have you tried different transformations? do they yield anything different?

[caitlinpohle]

Yes, none of them accurate....

[caitlinpohle]

I am sure they are in the same projection now but they still don't line up....

[JorgeOrellana]

I am all out of ideas in terms of getting things to line up better. The last conclusion I can make is that either the world imagery is not very accurate in  your area of interest or your shp file is innacurate. Sometimes data is captured from a really detailed data set or very course on too and when superimposed on top of other data, discrepencies can occur. Without know much more about how the data was created/obtained I don't know if there's much more I can help with.

Last thing I can  think of is acquiring additional data for the area and see how they all line up with one another, which can narrow down which data set is not accurate.

Jorge

[caitlinpohle]

I am working in Lisbon, the basemap with world imagery is from arcgis online for 2014 and the other layer is from the university. Isn't there anyway to georeference the layers to make them line up?

[eugeniosanchez]

As a test you can try to reproject the raster data (instead the shapefile) to make it the same projection than it  (you can do a clip on the raster to cover only your interest zone).

I had a similar problem with spanish raster and GPS data, and reprojecting the GPS data any way I could´t see the data coincidence; and reprojecting the raster (with the cost of the reprojection of raster each time it was repainted) they lined up perfectly.

[JorgeOrellana]

You would first need to decide which data is the most accurate, is it the imagery, or is it the shp file?

The issue is with the imagery being a map service and stored online you don't really have a way to georeference the image (unless you export your map as jpg/tif/etc) but you can end up losing the level of detail you need.

You could do a spatial adjust for the shp file (ArcGIS Desktop ) to see if that helps.

With either method you need points that are common to both data sets and if you don't have that, it will be impossible to georeference the two.