ArcGIS Remembers! And that costs you time!!!

What I did re last class Got a brand new layer called Subdivisions Got a brand new layer called Subdivisions Metadata says it is Metadata says it is NAD83_UTM_ZONE11_N NAD83_UTM_ZONE11_N CGS_NORTH_AMERICAN ’83 CGS_NORTH_AMERICAN ’83 Planar Coordinate Info Planar Coordinate Info Planer Distance Units: meters Planer Distance Units: meters Prj says, at the very end UNIT["Meter",1.0]] Prj says, at the very end UNIT["Meter",1.0]]

Then… Drag and drop into Map Drag and drop into Map Check properties of both the layer and the Data Frame Check properties of both the layer and the Data Frame Match Match Removed layer from Map… Removed layer from Map… THE PROJECTion ect. Of the DATA FRAME remained the same!!! THE PROJECTion ect. Of the DATA FRAME remained the same!!! This could be a booby trap This could be a booby trap

And then… In Catalog made a copy of subdivisons and called it… In Catalog made a copy of subdivisons and called it… Subdivision_no_prj Subdivision_no_prj Then… Then… Deleted prj Deleted prj Updated metadata – no change Updated metadata – no change Deleted xml Deleted xml Catalog made a new one but it was empty! Catalog made a new one but it was empty!

This means… That if you screw up a “define projection” then That if you screw up a “define projection” then The only way to repair the damage is to delete both the prj and the xml files and do the define projection thing again The only way to repair the damage is to delete both the prj and the xml files and do the define projection thing again Why does that work????? Or put another way… Why does that work????? Or put another way… Does “define projection” change the data? Does “define projection” change the data?

Ok, what next… After cleaning things up (deleted prj and xml) I… After cleaning things up (deleted prj and xml) I… Defined the subdivision_no_prj as Defined the subdivision_no_prj as NAD 27 UTM ZONE 11N NAD 27 UTM ZONE 11N Now that was a mistake Now that was a mistake

In ArcMap Removed subdivision – empty TOC and dataframe properties Removed subdivision – empty TOC and dataframe properties Added it back and… Added it back and… added subdivison_no_prj added subdivison_no_prj (remember, ArcMap thinks it is in NAD27 when the data is really in ’83) (remember, ArcMap thinks it is in NAD27 when the data is really in ’83) Whaaaat? Whaaaat? The two layers are bang-on top of each other – no error. The two layers are bang-on top of each other – no error. Hummmm  Hummmm 

Something funny here… Closed both Map and Catalog Closed both Map and Catalog Opened both Opened both Dragged both layers from Catalog to Map Dragged both layers from Catalog to Map Ah Ha!! Ah Ha!!

~200 M

So… That distance is possible in CA That distance is possible in CA BUT the main conclusions are BUT the main conclusions are 1. You have to delete both the prj and the xml if you need to remove the projection etc. info 2. Don’t clean the slate by Removing layers – DataFrame properties staythe same 3. ArcGIS REMEMBERS  so YOU must remember to CLOSE ArcMap when going to a new project --- Don’t trust New.