topic Reprojection Alignment Issues in Coordinate Reference Systems Questions

Reprojection Alignment Issues

BrandonColeman — Wed, 10 Sep 2014 15:54:50 GMT

I am having problems getting data to align properly with basemaps layers. The image below shows the difference between roads. The black lines are my centerlines shapefile, which is fairly off from the aerial underneath.

The centerlines shapefile's coordinate system is GCS_North_American_1983 while the basemap is WGS_1984_Web_Mercator_Auxillary_Sphere. I have tried projecting the centerlines shapefile into WGS_84 to get it to better align, but I don't believe I have gotten the transformation correct. I have tried using WGS_1984_(ITRF00)_To_NAD_1983 and NAD_1983_To_WGS_1984_5 transformations without much luck.

My data is in western Pennsylvania. I am looking for any help I can get so these line up. I am pretty sure it is a coordinate issue rather than the data provider digitized everything like this.

I am looking for suggestions on what I am to do next.

Re: Reprojection Alignment Issues

MelitaKennedy — Wed, 10 Sep 2014 17:15:32 GMT

The offset's way too large for NAD83 - WGS84. At most, those should differ by about a meter in the lower 48 states.

Any chance the shapefile is in NAD27 instead? Does everything look offset the same? If the offset differs in different areas, it could be a problem with either dataset--bad georeferencing of the imagery for instance.

Melita

Re: Reprojection Alignment Issues

BrandonColeman — Wed, 10 Sep 2014 18:00:39 GMT

Thanks for the advice Melita...

I panned through a lot more of the data, and the difference isn't uniform throughout the dataset. It does look like a bad georeference issue.

I will pan through my other layers to see if the difference is similar like this. If they are more uniform, I will check into NAD27 to see if that adjusts things properly.