Below are some problems and solutions that you may encounter
in the ArcMap environment as you analyze your data and compile
your report. The below won't solve all your problems, but it might
help with some. Give me feedback on the below and I will adapt
it so others can benefit. Don't forget to use your other resources
if the the above doesn't help.
Remember you are going to generate a lot of different files
- all part of your ArcMap project. Create a folder and put them
all in there. Also remember to back your project folder up, perhaps
at the end of every work session. Also, after saving your project,
or exporting data, check your filder to see what types of new
files have been created.
Creating your dbf:
- make sure your longitudes are negative (since we are west
of the meridian).
- use the Save As and select the dbf4. Give the file
a descriptive name.
- make sure your cell format is number with 5 decimal places.
Positioning the background air photos:
Background info: Raster data refers to images, which
are basically a bunch of color values for each pixel that together
make an image. You can download these from sites on the web. I
have downloaded several USGS air photos that should be useful
for your specific projects. They are available on one of the disks
in the lab. If you have georeferenced jpeg or other image file
you want to include as a layer the computer has to somehow know
what the geographic location of each pixel is. This information
is contained in an accompanying world file, and these can
often be downloaded from the web along with the image. This is
simply a text file containing the UTM coordinates of the upper
left corner, and the pixel scale distance. In order for ArcMAP
to recognize and use these they must have the a ".jgw"
suffix (e.g. sample.jpeg and sample.jgw. If you have both the
jpeg image file and the world file in your folder the following
Source of USGS
Steps to get your image 'positioned' in ArcMap:
- In the data view window of ArcMap under File, select
Add data. Navigate to the folder with your jpeg file and
select it. ArcMap should make an automatic connection to the
accompanying jgw file. While the two fils have different suffixes,
they must have the same name in order for ArcMap to connect them.
- A message about missing spatial info will come up. This is
because a coordinate system hasn't been selected for the image.
Latitude and longitude are angular measures of position. A coordinate
system, via some type of projection, plots points in a scaled
x,y plane. The following will allow you to establish a coordinate
system for your layers:
- Double left click on the Layers line at the top of
your layers menu. this controls properties for all your layers,
including map projection properties.
- A window comes up in which you will select a coordinate
system. Navigate through the following folders: predefined
-> projected coordinate system -> Utm ->
NAD 1983 -> NAD 1983UTMZone13N, and select this
last file. This will be your projection and coordinate system.
Getting the right suffix on your world
file - steps to take:
- If you have your computer set so that the file extensions
are visible then simply go in and change the txt extension to
jgw. A message will come up asking if you are sure you want to
do this. Reassure the computer that you do.
- If you can't see the file extensions the you need to navigate
to the folder where the files are kept and under the Tools
column select Folder Options, then View. Check
to see if the Hide file extensions ... box is checked.
If it is uncheck. You should now see all your file extensions.
then proceed as above.
Importing x, y data:
This is how you you get your dbf file information into ArcMap
so that you can play with it. In the ArcMap (data view window)
under Tools, select Add x,y data. Navigate to your
dbf file and select that. In the x coordinate and y coordinate
window latitude and longitude will likely show up automatically.
If not navigate to the column heading which has the appropriate
x and y values. Then reassure the program its OK, and your data
should show up in the Layers window to the left.
Zooming in on your data
For some reason if you try to zoom in on just portion of your
dbf data it will likely disappear. I have no idea of why. Perhaps
the programmers keep saying - "we should really fix this"
- but never got around to it. Anyway you need to "export"
your data so that ArcMap can work with it at any scale.
Here are the steps in order to do so:
right click on the listed layer.
select Export Data.
enter yes to the question if whether you want to add the
exported data to the list of layers.
rename the new layer.
turn off the original dbf generated layer so as to not get
now you can work with the export data file at any scale.
Plotting strike and dip symbols for your
faults and veins.
Here are the steps:
- right click on the layer with your data.
- select Properties at the bottom of the menu window.
- In the Layer Properties window select the Symbology
tab towards the top. Here is where you can do all sorts of magic
in terms of what plotted.
- If you click direclty on the small displayed symbol another
window opens up showing you the symbols you can select. The one
you want to use likely isn't there yet. Select the More Symbols
button and check the Geology 24k option (you might want
to deselect other symbol options to not have to search through
so many possibilities).
- Now scroll down throught the window of symbols and select
one of the strike and dip simples (there are quite a few to choose
from). Note that you can also change the color here.
- ArcMap still doesn't know how much to rotate them by. Select
the Advanced button in the Symbology menu and select Rotate.
Navigate through the listed field to the one with the strike
information and choose it. Now your symbols should plot correctly.