Introduction to Geographic Information Systems (GIS)
Continuing Education, July 2004
Class Announcements
Updated July 27, 2004
- 7/19/04
Tip about digitizing When digitizing
multiple feature classes in a geodatabase where many of the spatial
features need to align with each other and share vertices and edges, a
good strategy
is to digitize the most complex features first (the ones with the most
vertices and direction changes). Then
it is easier to make sure that additional features share the
appropritate
existing portions of the streets.
A wonderfully useful tool in this
regard is the Trace tool. Experiment with the Trace tool;
it's skillful use can really improve and speed the digitizing process.
- 7/19/04
Layers in Table of Contents in Map View
You may remember Randy's question Thursday night about how to have
layers (in his case 36 DOQQs) in a data frame but not have them listed
in the Table of Contents. I was sure this could be done, but so
far my investigation only shows that I was wrong. The layers in
the Legend in the Layout View can be shown or not while still being
displayed in the Layout, but I can't find any way to do something
comparable in the Table of Contents in the Map View.
In Layout View click Insert then Legend. A Legend Wizard will
display; choose the map layer to include in the legend, or right click
on an existing legend in the layout and click Properties and then Items
and choose the layers to be displayed in the legend.
- 7/14/04
Projections and Coordinate Systems
Although not listed in the Course Outline as one of the chapters
(tutorials) that I recommended that you study, based on comments in
class about the types of applications that you will have for GIS, I
suggest that you work through Chapter 13, Projecting data in ArcMap, to
help you understand how ArcGIS uses maps that have different coordinate
systems or projections in the same data frame.
In a nutshell, ArcMap changes projections "on the fly" (from among many
that are supported by ArcGIS) to match the coordinate system of
the data frame (which is set to be the coordinate system of
the first layer added to the data frame or to a system set directly by
the user). This assumes that the necessary information to define
the layer's coordinate system has been supplied (either in the metadata
of a geodatabase or in the .prj file of a shapefile). The ArcGIS
Toolbox has a section on Projections and supplies a wizard to help the
user define a dataset's projection/coordinate system if it has not
already been provided in metadata or a .prj file.
The "on the fly" projections are not as mathematically precise as a
permanent projection transformation; so if you plan to use a data
set for exacting analysis, it should be permanentally projected
to the required projection using the ArcToolbox Projection
Wizard. ArcView can do these permanent projection conversions for
shapefiles and geodatabase feature classes; other data formats require
ArcEditor or ArcInfo.
- 7/14/04
Using CAD files in ArcGIS
Most of you have said that you probably would need to import CAD files
into ArcGIS. We noted briefly on Tuesday that this can be done by
importing a CAD file into a geodatabase. Specifically:
- Start ArcCatalog
- Open an existing geodatabase or create a new geodatabase
- Right-click on the geodatabase name
- Click Import
- Choose CAD to Geodatabase
According to what I can find out in the ArcGIS help, it can only read
two formats of CAD. Those are .DXF (Drawing Exchange File) and
.DGN
(Interactive Graphics Design Software--Microstation Design File).
I
don't use CAD so I've never tried this, and I don't have any CAD files
to experiment with. If one of you could send me a CAD file
(attach to
an e-mail) or bring one to class (on a floppy or CD), we can try it to
see if there are any additional things to watch out for in this import
process.
The ArcGIS Help is fairly extensive. You can often find answers
to
your questions by exploring the Help Index for keywords.
- 7/14/04
Using MapInfo files in ArcGIS
ArcToolbox can import MapInfo Interchange Format (.MIF) files into
shapefiles. These shapefiles can then be used directly in ArcGIS
or
can be added to a geodatabase. So, make sure you get your MapInfo
data
in .MIF format, or have the person using MapInfo convert to shapefiles
before giving you the data (I think MapInfo can do that, but I'm not
absolutely sure). The import process would be as follows:
- Start ArcCatalog
- Click on the Tools command
- Click ArcToolbox (actually ArcToolbox can be started
directly
in
Programs without going through ArcCatalog)
- Click Import to Shapefile
- Choose MIF to Shapefile
- 7/6/04 For Thursday, July 8 If
possible, I recommend that you do the following between now and
Thursday's
class:
1) [Most important if you have limited
time--and
who doesn't] Go back over tutorials (chapters) 3 and 4.
2) Read the online (WWW) overviews of GIS,
coordinate
systems, and projections (see Reading Assignments in the syllabus).
3) Try some of the skills you learned in
Chapters
3 and 4 with different data. There's some generic data that comes
with
ArcGIS; it's in the folder at c:\arcgis\ArcTutor\Map. There's
some
Oklahoma and Tahlequah data sets on i:\ziehr\OK-data and
i:\zidehr\Tahlequah,
respectively.
- 7/6/04 ArcMap Error Message
When
trying to open an ArcMap document which was created (or saved) using
ArcMap
in the NET labs onto your home computer using the 180-day trial version
of
ArcGIS that came with your textbook you probably got (or will get) the
following
error message:
This happens because the map document refers to some extensions that
are
available on the full implementation version of ArcGIS that we are
running
in the lab, but that are not available on the trial version that came
with your textbook. Map documents created using the trial version
will open
and run correctly in the full version but not vice versa. I don't
know
of any direct solution. You might try creating a new copy of your
map
document (using save as) when you bring a map that you started at home
and
work on later in the NET lab. You still won't be able to open
this new
file at home, but at least you'll still have your original that you
started
at home.
- 7/4/04 Great websites for OK
data
Here's two great websites for downloading FREE spatial data for
Oklahoma.
We will talk more about them and use them both in class, but in case
you
want to explore now, here they are:
Oklahoma Center for
Geospatial
Information (OCGI) at OSU http://www.ocgi.okstate.edu/
Geo Information Systems
(applied research unit of the Sarkeys Energy Center at
OU) http://www.geo.ou.edu/
- 7/6/04 GIS
Monitor
A useful, weekly, online GIS newsletter called GIS Monitor is available
as
a free subscription at http://gismonitor.com/
. Their website also lists GIS jobs, back issues of the
newsletter,
and a variety of other GIS resources.
- 7/6/04 GIS
Lounge Here's a link to a good website from
which to find additional links
to GIS resources.
It's called GIS
Lounge; its URL is: http://gislounge.com/
.
- 7/6/04 NCGIA
Core
Curriculum The National Center for Geographic
Information
& Analysis had put together an online GIS Core Curriculum which
includes
an outline and notes regarding GIS essentials. It is a good
resource
that you should become familiar with. It will help you understand
some
of the concepts that the Theobold textbook may only skim or assume that
you
already know. The NCGIA
Core Curriculum can be accessed at <http://www.ncgia.ucsb.edu/giscc/>
- 7/6/04 Please check this page often
(at
least once a week). Important information pertaining to the
class,
especially revisions to assignments and cancelled classes, will be
posted
here. New announcements will be
listed
first. Older announcements will be retained but will be moved
farther
down the list.