THE DATA
The bathymetric data came from the NOAA website http://mapfinder.nos.noaa.gov.
To download this data – go into find maps and pick your area. This
map is a 1 arc second, 7.5 minute quad, datum - UTM NAD27 datum (zone 10)
in .dem raster grid file data format. This map was made from multiple
surveys from 1934-1982 and gridded to 30 meters. In this case, we
were lucky that it came in directly as a .dem file.
The topographic .dem data is not as easy to come by. I got my data from a University of Washington, Seattle webpage http://duff.geology.washington.edu/data directly as a .dem file. However, if you cannot find some local university geography or geology webpage that has these, it is tough to get these files into a format that ARCVIEW can use. The following is a procedure for translating USGS 7.5 minute quad SDTS raster data into .dem files. Again, these files are in NAD27 datum (zone 10) with 30 meter resolution.
TRANSLATING USGS .SDTS FILES TO .DEM FORMAT FOR USE IN ARCVIEW
A good site to get all the USGS .dem quads in the country is http://edcftp.cr.usgs.gov/pub/data.
There are a variety of sites where you can find this USGS SDTS data.
This data is stored in .tar.gz compressed files that will unpack into a
series of .ddf files. What the heck are these you ask??? Good
question! Now that you have these you will need to convert one of
these (the ####CEL0.ddf – that’s ell zero for the last 2 characters in
the main name) to a .dem file.
In order to do this, you have to go out to a website http://www.engineering.usu.edu/cee/faculty/dtarb/SDTSext.html
and download a utility to stick in your extensions file in order to do
this. Full instructions on how to do this appear on this site.
Basically take the file sdts.avx and stick it in the esri ARCVIEW program
folder called ‘Ext32’ (with all other arcview extension programs that you
have) and then stick file sdts.dll in the esri ARCVIEW folder called ‘Bin32’
(with all the other .dlls). Then open ARCVIEW – go into file – extensions
and add the SDTS extension. Then you can use the import function
under file in the menu to import SDTS files. Bingo!
DOWNLOADING AND UNPACKING
In order to download some of this data you will need winzip to unpack
.zip compressed files and in some cases pkzip to unpack .tar and .gx files.
(Note that .tar files need to be unpacked 2X.) These 2 programs are
readily available at a variety of websites for you to download for free
if you do not yet have them on your computer.
IMPORTING DATA INTO ARCVIEW
Once you have your .dem files, load up your view window in your project,
then go under file and click on import. Pick DEM as your file and
go get your files (one at a time) and then ARCVIEW will ask you to give
them a grid name and then ask you if you want to add it as a new theme
to your view – say yes and away you go! Now just add your next file.
OVERLAYING
Follow the instructions from image #1 details on the webpage.