topic Re: DEM CONTOURS in ArcGIS Spatial Analyst Questions

DEM CONTOURS

ChuckTurlington — Fri, 05 Feb 2016 14:31:43 GMT

Hello,

I am using ArcMap 10.2.1.

I have displayed some contours from a DEM and right clicked on the contour layer to select Export Data. The USGS NED metadata states the data coordinate is NAD83, vertical datum is NAVD88 and the Altitude distance units are Meters. The ArcMap data frame coordinates are set to NAD83, South Carolina, International Feet. In the export dialog I select "Use the same coordinate system as: the data frame," and select the output location and shape file format. However, when I import the contours into CAD the horizontal location of the contours appears correct but the elevation of the contours appears to be in meters. What is the best way to export the contours so they have the correct coordinate and units?

Re: DEM CONTOURS

DanPatterson_Retired — Fri, 05 Feb 2016 14:54:29 GMT

was there an option to scale the Z values? if so use 0.3048 which I think is the US foot to meter conversion

PS just checked apparently it doesn't Adding x,y coordinate data as a layer—Help | ArcGIS for Desktop

However in the Copy Features tool, you can specify a different coordinate system by going to the Environments Tab and selecting the coordinate system you want and choosing the correct Z type

Re: DEM CONTOURS

ChuckTurlington — Sun, 07 Feb 2016 15:18:26 GMT

Dan,

I found using the Z-factor was the best way to adjust the vertical units of contours in a dem. When creating the contours thru Spacial Analyst Tools_>Surface->Contours, the contour dialog has a Z-Factor entry option, this is where I used 3.28084 to convert from meters to feet. There is also a Hillshade option under Surface as well, that is supposed to accomplish the same adjustment, but when I tried that option, my data size was expanded significantly to where I could not work with it. The Z-Factor worked well, I had problems with it.