It seems this topic has been covered a fair bit in this forum but I haven't found anything that has helped yet. I have 30 sec and 1 minraster layers of bathymetry from GEBCO 08 Grid data that I'm trying to convert to slope layers. I've imported the raster bathymetry layer into ArcMap and with a spatial reference of GCS_WGS_1984 (Angular unit degree, Datum D_WGS_1984). I've tried to calculate the slope for the area but all my values are unrealistic i.e. most values are around 89 degrees or up to 2000% when calculated as a percent. I think this has something to do with the z value but I'm not sure what else to do. I've tried defining the z units for the grid as in this article, http://support.esri.com/es/knowledgebase/techarticles/detail/30566 ...with no luck.
Does this have something to do with the fact the raster layer has the GCS_WGS_1984 spatial reference? I understand the x,y and z units must be the same but I'm not sure what to change to do this.
You have your X Y units were in decimal degrees and Z units in meters/feet. In this case, you will either have to use appropriate Z-factor for particular latitudes or Re-project the input raster to a projected coordinate system and run slope again.
